TWI299435B - Positive photoresist composition and resist pattern formation method - Google Patents

Description

1299435 (1) Description of the Invention [Technical Field of the Invention] The present invention relates to a positive-type photoresist composition and a method of forming a photoresist pattern using the positive-type photoresist composition. [Prior Art]

In the process of manufacturing semiconductor elements and liquid crystal display elements in recent years, miniaturization has been rapidly promoted as lithography technology progresses. The miniaturization method generally has a short wavelength of the exposure light source. Specifically, the ultraviolet rays represented by the g-line and the i-line were previously used, and now a KrF excimer laser (248 nm) was introduced, and an ArF excimer laser (193 nm) was started. A known material that conforms to a high resolution condition capable of reproducing a fine-sized pattern, such as a base resin which can be changed to an alkali-soluble resin by an acid in an organic solvent, and a chemically-enhanced light of an acid generator which generates an acid under exposure. Blocking composition. A chemically-enhanced positive-type photoresist composition which has been proposed to be used as a method for laser exposure using KrF excimer laser is generally used in a polyhydroxystyrene-based resin for a basic resin, and a part of the hydroxyl group is protected by an acid-dissociable dissolution inhibiting group. (For example, refer to Patent Document 1). Further, the acid dissociable dissolution inhibiting group is mainly used, an acetal group such as a chain ether group represented by 1-ethoxyethyl group or a cyclic ether group represented by a tetrahydropyranyl group, or tert-butyl group. The tertiary alkyl group represented by the above, the tertiary alkoxycarbonyl group represented by tert-butoxycarbonyl group, and the like. Patent Document 1: JP-A-H05-249682 (2) 1299435 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION In recent years, improvements in photoresist have been demanded in response to the gradual miniaturization of photoresist patterns and the demand for higher resolution. The rectangular shape of the pattern, the shape of the side wall surface of the line pattern, the edge roughness (LER) and other shape problems, the depth of focus (D OF), and the dimensional change of the pattern are safe for the exposure amount representing the amount of change in the exposure amount within a certain range. The coefficient (EL safety factor) is an important issue.

In view of the above, an object of the present invention is to provide a positive photoresist composition having high resolution and capable of improving at least one of a rectangular shape, an LER, a DOF, and an EL safety factor of a photoresist pattern, and a photoresist pattern. Forming method. Means for Solving the Problems In order to achieve the above object, the present invention consists of the following. That is, the positive-type photoresist composition of the present invention is characterized in that it contains a resin component (A) which can increase alkali solubility under the action of an acid, and a positive photoresist composition of an acid generator component (B) which generates an acid under exposure. The resin component (A) contains a constituent unit (a1) having a phenolic hydroxyl group, a constituent unit (a2) containing a monocyclic or polycyclic group containing a lactone, and a composition containing an acid dissociable dissolution inhibiting group. Copolymer (A1) of unit (a3). The method for forming a photoresist pattern of the present invention is characterized in that after forming a positive-type photoresist film on the substrate by using the positive-type photoresist composition of the present invention, the positive-type photoresist film is selectively exposed to light, and then the image forming process is performed. Form a photoresist pattern. Further, in the present invention, "exposure" includes an irradiation electron beam. “Units and “constituting units” refer to the monomer units that make up the polymer. -5- (3) 1299435 Effect of the Invention The present invention can provide a positive photoresist composition having high resolution and which can improve the rectangularity of the resist pattern, the LER, the DOF, and the EL safety factor. The formation method of the photoresist pattern. BEST MODE FOR CARRYING OUT THE INVENTION The positive resist composition of the present invention contains a resin component (A) which can increase alkali solubility under an action of an acid, and an acid generator component (B) which produces an acid under exposure. (hereinafter also referred to as (Α) component) The resin component (Α) contains a constituent unit (a 1) containing a phenolic hydroxyl group, a constituent unit (a2) containing a monocyclic or polycyclic group containing a lactone, and The copolymer (A1) (hereinafter also referred to as (A1) component) of the constituent unit (a3) of the acid dissociable dissolution inhibiting group.

(A) When the component is subjected to the acid generated by the component (B) under exposure, the acid dissociable dissolution inhibiting group contained in the component (A 1) is dissociated, and the component (A) is changed from alkali insoluble to alkali soluble. . Therefore, when the photoresist pattern is formed, when the mask is exposed or heated after exposure, the exposed portion can be converted into alkali-soluble and the unexposed portion can maintain alkali-insolubility, so that a positive light can be formed after alkali development. Resistance pattern. • (A 1) component <constituting unit (al)> -6 - 1299435 The constituent unit (a 1) is a constituent unit containing a phenolic hydroxyl group, preferably a constituent unit represented by the following general formula (1) (al-Ι) ), that is, the constituent unit derived from (2-methyl)hydroxybenzene.ethylene. The "(α-methyl) hydroxystyrene" means one or both of hydroxystyrene and methoxy-styrene. In other words, "(α-methyl)hydroxystyrene" is a general term for hydroxystyrene and α-methylhydroxystyrene, and "constituting units derived from (α-methyl)hydroxystyrene" as in the general formula (I). As shown, it is a constituent unit composed of an ethylene double bond in (α.methyl)hydroxystyrene. The position of the hydroxyl group in the constituent unit (a1) may be 0-position, m-position or Ρ-position', but it is preferably a P-position which is easy to obtain and has a low price.

(wherein R is a hydrogen atom or a methyl group) <Constituent unit (a2)> The constituent unit (a2) is a constituent unit containing a lactone-containing monocyclic or polycyclic group. The monoester- or polycyclic group containing a lactone in the present invention means a monocyclic group formed by a lactone ring or a polycyclic group having a lactone ring. At this time, the lactone ring means a ring containing a -C0-0 structure and is calculated by one unit ring. Therefore, it is referred to as a lactone-containing monocyclic group only when formed from the inner 8 (5) 1299435 ester ring, and the structure is referred to as a lactone-containing polycyclic group without other ring structures. _ The constituent unit (a2) is preferably a constituent unit (a2-1) represented by the following general formula (II), that is, a hydrogen atom in the hydroxyl group of (meth)acrylic acid is subjected to X (monoester or poly-cyclic group containing lactone) a constituent unit derived by substituting (meth)acrylic acid. In the present specification, "(meth)acrylic acid" means one or both of methacrylic acid and acrylic acid. In other words, "(meth)acrylic acid" is a generic term for methacrylic acid and acrylic acid. In the present specification, "(meth) acrylate" means one or both of methacrylate and acrylate. In other words, "(meth) acrylate" is a generic term for methacrylate and acrylate.

(wherein R is a hydrogen atom or a methyl group, and X is a lactone-containing monocyclic or polycyclic group.) Specifically, the constituent unit (a2) is preferably a constituent unit represented by the following general formula (IV) (a2-l) 1), the following constituent unit (a2-12) of the general formula (V), the constituent unit (a2-13) represented by the following general formula (VI), and the constituent unit (a2-14) shown by the following general formula (VII) At least one of the groups selected. Particularly preferred is a constituent unit (a2-13) represented by the general formula (VI). (6) 1299435

m (wherein R is a hydrogen atom or a methyl group)

R

, carboxy oxygen bond The general form of the compound of the formula (VI) is a mixture of the isomers at the 5-position or the 6-position. (wherein R is a hydrogen atom or a methyl group) -9- 8 (7) 1299435

(wherein R is a hydrogen atom or a methyl group) <Constituent unit (a3)> The constituent unit (a3) is a constituent unit containing an acid dissociable dissolution inhibiting group. The constituent unit (a3) is not particularly limited, and a hydroxystyrene resin for a base resin of a chemically strengthened type and a positive resistive composition for KFF and a positive resistive composition for ArF can be suitably used. The acrylic resin contains a constituent unit of an acid dissociable dissolution inhibiting group. The constituent unit (a 3 ) is preferably a constituent unit (a3-1) represented by the following general formula (111), that is, a hydroxyl group hydrogen atom of (α-methyl)hydroxystyrene is subjected to Y (acid dissociable dissolution inhibiting group) The constituent unit of the substitution, and the constituent unit (a3-2) represented by the following general formula (iii), that is, the constituent unit in which the hydrogen atom in the carboxyl group of (meth)acrylic acid is substituted by γ (acid dissociable dissolution inhibiting group) At least one. Particularly preferred are the constituent units (a3-l) shown in the following general formula (II). -10- 1299435

(wherein R is a hydrogen atom or a methyl group, and Y is an acid dissociable dissolution inhibiting group)

(wherein R is a hydrogen atom or a methyl group, and Y is an acid dissociable dissolution inhibiting group). The acid dissociable dissolution inhibiting group Y is specifically, for example, an alkoxyalkyl group, preferably a 1 β alkoxy group, a grade 3 Oxide ore base, grade 3 yard, grade 3

An oxycarbonylalkyl group, a cyclic ether group or the like. Position-dependent chain The 1-alkoxyalkyl group has a structure in which the following general formula (VIII) is substituted, branched or cyclic alkoxy groups. (VIII) r°-R2 (wherein R1 is a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, and R2 is a chain, branched or cyclic alkyl group having 1 to 12 carbon atoms, and an alkyl group of R1 The end may be bonded to the chain or branched alkyl end of R2 to form a ring). -11 - (9) 1299435 Specifically, for example, 1-methoxyethyl, 1-ethoxyethyl, i-iso-propoxyethyl, 1-n-butoxyethyl, l-tert- 1-oxyl group such as butoxyethyl, methoxy, methyl, ethoxymethyl, iso-propoxymethyl, n-butoxymethyl, m, tert_butoxymethyl, etc. Alkyl; 1-cyclopentyloxyethyl, 1-cyclo-hexyloxyethyl, 1-tricyclo[5.2.1.02,6]nonyloxyethyl, cyclopentyloxymethyl, cyclohexyloxy a 1-alkoxyalkyl group having an alicyclic structure such as a methyl group or a tricyclo[5·2·1·02'6]nonyloxymethyl group; a f-cyclic ether group such as a tetrahydropyranyl group or a tetrahydrofuranyl group; . The above-mentioned tertiary alkyl group is, for example, a tert-butyl group, a tert-pentyl group or the like, a chain 3 alkyl group; 1-methyl-1-cyclopentyl group, 1-ethyl-1-cyclopentyl group, 1·methyl group -丨_cyclohexyl β, 1-ethyl-1-cyclohexyl, 2·methyl-2·adamantyl, 2-ethyl-2-adamantyl, 2-propyl-2-adamantyl, 2- (1-adamantyl)_2_propyl, 8-methyl-8-tricyclo[5·2·1·02'6]decyl, 8-ethyl-8-tricyclo[5.2.1.02,6] Mercapto, 8-methyl-8-tetracyclo[4·4·0·12'5·17'1ϋ]dodecyl, 8-ethyl-8-tetracyclo[4·4·0·12 ' 5·17 '1G] a tertiary alkyl group having an alicyclic structure such as dodecyl group. A tertiary alkoxycarbonyl group such as tert-butoxycarbonyl, tert-pentyloxycarbonyl or the like. A tertiary alkoxycarbonylalkyl group such as tert-butoxycarbonylmethyl, tert-pentyloxycarbonylmethyl or the like. Further, it is preferably a 1-alkoxyalkyl group and a tertiary alkyl group having excellent resolution properties, particularly preferably a 1-alkoxyalkyl group, most preferably a 1-ethoxyethyl group. In the positive resist composition of the present invention, the ratio of the constituent units (a2) constituting all the constituent units of the copolymer (A1) is preferably from 5 to 50 mol%, more preferably from 12 to 8 (10) 1299435. It is 10 to 30 mol%. When the constituent unit (a2) exceeds this range, the solubility in the developing solution will be insufficient, and the resist pattern may not be formed. Also, when it is small, the effect of using the constituent unit (a2) sufficiently cannot be obtained. In order to ensure good solubility in the developing solution, the total ratio of the constituent units (al) and (a3) constituting all the constituent units of the copolymer (A1) is preferably 40 to 95 mol%. More preferably, it is 50 to 90% by mole.

The ratio of the constituent unit (a3) of the total of the constituent units (al) and (a3) is preferably from 5 to 50% by mole, more preferably from 10 to 30% by mole. When the ratio of the constituent unit (a3) is less than or equal to the upper limit of the range, in particular, a good resistive pattern-shaped rectangular shape can be obtained after development, and the development defect (瑕疵) of the photoresist pattern after development can be effectively prevented. Further, when the constituent unit (a3) is at least the lower limit of the range, good resolution performance can be obtained. The total amount of the constituent unit (al), the constituent unit (a2) and the constituent unit (a3) in the copolymer (A1) is preferably 80 mol% or more for all the constituent units constituting the copolymer (A1). When it is less than 80 mol%, the resolution tends to deteriorate. The total amount of the constituent unit (al), the constituent unit (a2), and the constituent unit (a3) is preferably 90 mol% or more, and most preferably 1 mol%. <Other constituent unit (a4)> The copolymer (Al) may contain a constituent unit having an acid-safe dissolution inhibiting group (a4) in addition to the constituent unit (al), the constituent unit (a2), and the constituent unit (a3). . The constituent unit (a4) is not particularly limited, and a conventional chemically-reinforced KrF positive-type photoresist composition and a positive-type photoresist group for ArF-13-(β) (11) 1299435 can be suitably used. A constituent unit having an acid-safe dissolution inhibiting group in a hydroxystyrene resin or a (meth)acrylic resin for a resin. The constituent unit (a 4) is preferably a constituent unit (a4-1) represented by the following general formula (IX), that is, a constituent unit derived from (α-methyl)styrene, and a composition represented by the following general formula (ix) The unit (a4-2), that is, at least one selected from the constituent units in which the hydrogen atom in the carboxyl group of (meth)acrylic acid is substituted by Z (acid-safe dissolution inhibiting group).

Among them, the unit (a4-l) is particularly preferable as shown in the general formula (IX) having excellent dry etching resistance. Further, the acid-stable dissolution inhibiting group refers to a group which does not dissociate under the action of an acid.

(IX) (wherein R is a hydrogen atom or a methyl group, R3 is a linear or branched alkyl group having 1 to 5 carbon atoms, and η is an integer of 0 or 1 to 3) (12) 1299435

R

(χ) (wherein R is a hydrogen atom or a methyl group, and Z is an acid-safe dissolution inhibiting group).

R3 in the general formula (IX) is a linear or branched alkyl group having 1 to 5 carbon atoms, specifically, for example, methyl, ethyl, propyl, isopropyl, η-butyl, isobutyl, tert- Butyl, pentyl, isopentyl, neopentyl and the like. Industrially preferred is methyl or ethyl. η is an integer of 0 or 1 to 3, preferably 0 or 1, and industrially preferably 0. Further, when η is from 1 to 3, the substitution position of R3 may be a 〇-position, an m-position or a P-position, and when η is 2 or 3, the substitution position may be arbitrarily combined. Specific examples of the acid-safe dissolution inhibiting group in the general formula (ix) are, for example, a linear or branched alkyl group such as a methyl group, an ethyl group or an isopropyl group; a cyclopentyl group, a cyclohexyl 'isobornyl group, and a tricyclic ring. [5·2·1·02 '6] an alkyl group having an alicyclic structure such as a fluorenyl group, a 2-adamantyl group, or a tetracyclo[4·4·0·12' 5·17' 1G] dodecyl group. The constituent unit (a4) of the present invention is not essential, but it can improve the focus coating degree and enhance the dry contact resistance. When the constituent unit (a4) is used, the ratio of the constituent unit (a4) of all the constituent units constituting the copolymer (A1) in the copolymer (A1) is preferably 〇.5 to 1 〇 mol%, more preferably 2 to 5 moles %. When the constituent unit (a4) exceeds this range, the solubility in the developing liquid tends to deteriorate. The mass average molecular weight Mw of the copolymer (A1) (calculated by gel permeation chromatography-15-(13) 1299435 (GPC) in terms of polystyrene, the same applies hereinafter), and is preferably 3,00 To 30,000, more preferably 5,000 to 20,000. Further, the degree of dispersion of the copolymer - (A1) (Mw/Mn ratio, Μη is a number average molecular weight) is preferably such that the dispersion is small and good resolution is obtained. Specifically, it is preferably 2.0 or less, and more preferably 1.7 or less. The method for producing the copolymer (Α1) may be that [1] corresponds to a monomer constituting the unit (al), corresponds to a monomer constituting the unit (a2), and corresponds to the constituent f unit (a3) without introduction of acid dissociation. The method of protecting the hydroxyl group or the carboxyl group of the constituent unit (a3) with an acid dissociable dissolution inhibiting group after copolymerization of the constituent unit of the dissolution inhibiting group state; [2] Modulation corresponds to pre-introduction of acid dissociation dissolution inhibition After the monomer of the constituent unit (a3), the monomer corresponds to a method of copolymerizing a monomer constituting the unit (al) and a monomer corresponding to the constituent unit (a2); [3] is equivalent to the composition The monomer of the unit (a3) and the monomer corresponding to the constituent unit (a2) are subjected to copolymerization, hydrolysis, or the like, and a part of the substituent of the constituent unit (a3) protected by the acid dissociable dissolution inhibiting group is converted into a hydroxyl group to be purified. f unit (al) method, etc. The polymerization method is not particularly limited, but it is preferred that the radical polymerization is preferred. In particular, a solution in which a raw material monomer, a polymerization initiator, a polymerization catalyst, and a chain transfer agent are dissolved in a polymerization solvent is subjected to radical polymerization, and at this time, for example, all monomers, a polymerization initiator, and a polymerization catalyst may be used. And the chain transfer agent is dissolved in the polymerization solvent and heated to the polymerization temperature, that is, the polymerization method is used, or the monomer is dissolved in the solvent, heated to the polymerization temperature, and then added with a polymerization initiator, a polymerization catalyst, and a chain transfer agent. Alternatively, a monomer, a polymerization initiator, a polymerization catalyst, a chain transfer agent may be partially or wholly mixed or separately dropped into a polymerization system heated to a temperature of poly-16-(14) 1299435, that is, a dropping polymerization method or the like. Among them, the drop polymerization method can improve the reproducibility of each batch of the product, and it is particularly preferable to separately inject the monomer, the polymerization initiator of the radical generating source, the polymerization catalyst and the chain transfer agent, and the part is 'alone. Drop method. Further, all or a part of the polymerization catalyst, the polymerization initiator, and the chain transfer agent may be supplied to the polymerization system before the supply of the polymerizable monomer. Since the dropping method can change the supply rate in accordance with the concentration and composition of the monomer in the polymerization system, the radical concentration, etc., the molecular weight distribution of the copolymer and the composition of the dP can be controlled. In the case of radical polymerization, the polymerization initiator used is, for example, 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2-methylbutyronitrile), 2,2,- Dimethyl azobisisobutyrate, 1,1'-azobis(cyclohexane-b-carbonitrile), 4,4,_azo double (4_

Azo compounds such as cyanovaleric acid; hydrazine peroxide, lauryl peroxide, phenylhydrazine peroxide, bis(3,5,5-trimethylhexyl) peroxide, succinic acid peroxidation Separately or as a mixture of organic peroxides such as tert-butyl peroxy-2-ethylhexanoate. Further, the chain transfer agent used is, for example, dodecyl mercaptan, mercaptoethanol, mercaptopropanol, mercaptoacetic acid, mercaptopropionic acid, 4,4-bis(trifluoromethyl)-4-hydroxyl Separately or as a mixture of known thiol compounds such as 1-thiol. The solvent used for the radical polymerization may be a solvent which can stably dissolve the raw material monomers, the obtained copolymer, the polymerization initiator and the chain transfer agent, and is not particularly limited. Suitable solvents are, for example, alcohols such as methanol, ethanol, and isopropanol; ketones such as acetone, methyl ethyl ketone, methyl amyl ketone, and cyclohexanone; tetrahydrofuran, dioxane, polyether, and propylene glycol-A Ethers such as ethers, esters such as ethyl acetate and ethyl lactate; ether esters such as propylene glycol methyl ether acetate; lactones such as butyl-17-(15) 1299435 lactone, and Or mixed use. The polymerization conditions are not particularly limited, and a general polymerization temperature is from 40 ° C to 1 〇〇 ° C. The polymerization time may vary depending on the polymerization method, and therefore cannot be specified. For example, when the polymerization is included, the reaction time after reaching the polymerization temperature may be from 1 to 24 hours, preferably from 2 to 12 hours. When the dropping liquid is polymerized, the monomer composition, the concentration, and the radical concentration in the polymerization system can be kept constant, and the monomer composition and molecular weight generated during the dropping time are preferably f. However, when the dripping time is too long, the production efficiency per unit of time and the stability of the monomer in the drip are not favorable. Therefore, the dropping time is 〇5 to 25 hours ‘preferably 1 to 10 hours. Since the unreacted monomer remains after the completion of the dropping, it is preferred to carry out the aging at a maintenance polymerization temperature. The ripening time may be within 8 hours, preferably 1 to 6 hours.

Since the copolymer obtained by the polymerization contains low molecular weight impurities such as unreacted monomers, oligomers, polymerization initiators, chain transfer agents, and reaction by-products thereof, it is preferably removed by a purification step. At this time, the desired good solvent may be added to dilute the polymerization reaction solution, and then contact the weak solvent to precipitate the copolymer as a solid, and then extract the impurity (hereinafter referred to as reprecipitation) from the weak solvent phase, or in a liquid-liquid two-phase manner. Solvent phase extraction of impurities. In the case of reprecipitation, the precipitated solid may be separated by a solvent by filtration or decantation, and then the solid is re-dissolved in a good solvent and then added to a weak solvent, or washed with a mixed solvent of a weak solvent, a good solvent and a weak solvent. The solid step is refined. Further, in the liquid-liquid two-layer separation, the weak solvent phase can be separated by a liquid separation method, and a weak solvent or a mixed solvent of a good solvent and a weak solvent is added to the obtained copolymer solution for reprecipitation or liquid-liquid two-phase separation to be purified. This step can be repeated or combined with different steps. -18- (16) 1299435 The method for protecting the hydroxyl group of the copolymer by an acid dissociable dissolution inhibiting group may be a P-toluenesulfonic acid, a trifluoroacetic acid, a strongly acidic ion exchange resin, etc. [1] A method of reacting a copolymer obtained by the method with a compound which imparts an acid dissociable group such as a vinyl ether or a halogenated alkyl ether. 'The method of changing the acid dissociative dissolution inhibitory group of the copolymer to a hydroxyl group may be a copolymer obtained by the method [3] in the presence of a known acid catalyst such as P-toluenesulfonic acid, trifluoroacetic acid or a strongly acidic ion exchange tree. A method in which a substance reacts with water and a solution of water is added. Among them, a method in which a copolymer containing constituent units (al) and (a2) is prepared by the method of [1], and a copolymer (A1) is obtained by reacting with an alkyl vinyl ether under the above-mentioned acid catalyst is preferred. The solvent used in the reaction may be a solvent capable of dissolving the copolymer, and is not particularly limited. Suitable solvents are, for example, those indicated by the polymerization solvent. The reaction conditions are not particularly limited. Generally, the reaction temperature may be from 0 to 100 ° C, but the influence of the acid catalyst on the solvent and the stability of the production are considered, which is preferably from 0 to 8 ° C. 〇 to 60 ° C. The reaction time will vary depending on the temperature of the reaction, and the time to achieve the desired reaction rate can be selected. After the reaction, the reaction solution may be contacted with a known basic compound or an anion exchange resin to remove the acid catalyst. If necessary, a filter having an average pore diameter of 5·5 μΐΏ or less, preferably 0.1 μη or less, may be passed through to remove extremely small solid components and insoluble foreign matters. Further, by contacting a filter having a positive word potential, a resin having an ion exchange group, a filter, or the like, the metal component can be removed. Further, when necessary, a solution for forming a coating film having a predetermined concentration can be obtained by distilling off a low boiling point component such as -19-(17) 1299435 while supplying a solvent for forming a coating film. The solvent for forming a coating film is not particularly limited as long as it can dissolve the copolymer, and is generally selected based on the boiling point, the influence on the semiconductor substrate and other coating films, and the radiation absorbability for lithography. The solvent for forming a coating film to be used is generally a solvent such as propylene glycol methyl ether acetate, ethyl lactate, propylene glycol monomethyl ether, methyl amyl ketone, 7-butyrolactone or cyclohexanone. The amount of the solvent to be used is not particularly limited, and is usually from 1 part by mass to 20 parts by mass per part by mass of the copolymer.

In the above-mentioned positive-type resist composition, in addition to the copolymer (A1), a component other than the copolymer (A1) may be appropriately added to a positive resist composition such as a polyhydroxystyrene resin or a (meth)acrylic resin, but In the component (A) contained in the positive resist composition, the copolymer (A1) is preferably 80% by mass or more, more preferably 90% by mass or more, and most preferably 100% by mass. The ratio of the component (A) in the positive resist composition can be appropriately adjusted depending on the purpose and the thickness of the photoresist film. • Acid generator (B) (hereinafter also referred to as (B) component) (B) The known acid generator used in the prior chemically-reinforced photoresist composition can be used without particular limitation. Known acid generators such as iron iodide salts, barium salts, etc., salt generators, sulfonate acid generators, dialkyl or diarylsulfonium diazomethanes, poly(disulfonium) A diazomethane acid generator such as diazomethane, a nitrobenzylsulfonate acid generator, an imidosulfonate acid generator, or a bismuth acid generator. -20- (18) 1299435 § The specific salt generator is, for example, diphenyliodo-trifluoromethanesulfonate or nonafluorobutanesulfonate; bis(4-tert-butylphenyl) Iodine III. fluoromethanesulfonate or nonafluorobutanesulfonate; triphenylmethane trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; tris(4-methyl a trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; dimethyl(4-hydroxynaphthyl)phosphonium trifluorobutanesulfonate, heptafluoropropanesulfonate , nonafluorobutane sulfonate; triphenylmethanesulfonate, heptafluoropropane sulfonate or nonafluorobutane sulfonate; diphenylmethylhydrazine trifluoromethanesulfonic acid a salt, heptafluoropropane sulfonate or nonafluorobutane sulfonate; (4-methylphenyl)diphenylphosphonium trifluoromethanesulfonate, heptafluoropropane sulfonate or nonafluorobutane sulfonate; -Methoxyphenyl)diphenylphosphonium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; tris(4-tert-butyl)phenylhydrazine trifluoromethanesulfonic acid Salt, heptafluoropropane sulfonate Salt or nonafluorobutane sulfonate. Specific examples of the sulfonate-based acid generator are, for example, α-(methylsulfonyloxy Φimino)-phenylacetonitrile, α-(methylsulfonyloxyimino)-ρ-methoxy Phenyl acetonitrile, α-(trifluoromethylsulfonyloxyimino)-phenylacetonitrile, α-. (trifluoromethylsulfonyloxyimino)-ρ-methoxyphenylacetonitrile, --(ethylsulfonyloxyimino)-fluorene-methoxyphenylacetonitrile, α-(propylsulfonyloxyimino)-ρ-methylphenylacetonitrile, α-(methyl Sulfomethoxyimino)-indole-bromophenylacetonitrile, bis-indolyl-(η-butylsulfonyl)dimethylglyoxime, and the like. Of these, (methanesulfonyloxyimino)-fluorene-methoxyphenylacetonitrile is preferred. Among the diazomethane acid generators, specific examples of the dialkyl or diarylsulfonyl diazomethanes are, for example, bis(isopropylsulfonyl)diazomethane and di(p-

-21 - (19) 1299435 toluene sulfonate) diazomethane, bis(1,1-dimethylethyl sulfonate)~extension s oxazine, bis(cyclohexylsulfonyl)diazomethane, Bis(2,4-dimethylbenzene^saidoxime)diazomethane. Poly(disulfonium)diazomethanes have the following structures, for example, 1,3,

Bis(phenylsulfonium diazomethylsulfonyl)propane (Compound A, decomposition point 135 ° C), 1,4-bis(phenylsulfonyldiazomethylsulfonyl)butane (compound b, Decomposition point 147 ° C), 1,6-bis(phenylsulfonyldiazomethylsulfonyl)hexane (Compound C, melting point 132t, decomposition point 145 ° C), 1,1 〇 _ bis (phenyl Sulfonium diazomethylsulfonyl) brothel (Compound D, decomposition point 147 ° C), I, 2-bis(cyclohexylsulfonyldiazomethylsulfonyl)ethane (Compound E, decomposition point 149 〇), bis(cyclohexylsulfonyldiazomethylsulfonyl)propane (compound F 'decomposition point 153 ° C), 1,6-bis(cyclohexylsulfonyldiazomethylsulfonium)hexane ( Compound G, i.e., 9 ° C, decomposition point U2C), bis(cyclohexylsulfonyldiazomethylsulfonyl) decane (compound oxime, decomposition point 1 16 ° C), and the like.

-22- (20)1299435

Compound A 〇 n2 〇 Ο Ν2 Ο Υ ιι2 ιι , , ιι ιιζ ιι / ΓΛ S — C—S — (CH2)3 —S — 0 A S-V y II Jl Η Η \=/

ο Ο 〇 O Compound B 〇 N — n II II2 II , , H 11^ Μ /T\ (/ γ-S —C —S —(CH2)4 —S —C —y

O 0 〇 n2 o \_/ )! O Compound c II o o I! o o 1] \-/ o '7\λΛ2Λ-·(〇η2), -ΪΛ-1-/Λ o

Compound D o Ο

G Ο “— C—S — (Ch^)T. One tube one ό one γ ^===^ 〇 Ο Ο Ο ο

Q Ο

口 Ε Ν 〇 Ο Ν 2 Ο

All II2 II , , Η )Ι II

S — CS —(CH2)2 — SCS II II II H 〇Ο Ο 化合物 Compound F Ο Ν 〇Ο Ν2 Ο _ / \-SC一羞一(CH2)3 — έ One C-S 〉 \^j\\ » « ιι w xf 〇ooo

Compound G 〇O _ A J\ ϊ !I2 II , , « n / V 〇-?-c-r(GH2)6 —f _c_f Nf Ο Ο 〇〇 compound H 〇〇H+( N~' ο O Ψ oo π*2 Π /~\CH2)i<r*S — c One yoo (B) component can be used alone or in combination of two or more. Among them, it is preferred that the component (B) contains a diazomethane acid generator. When the above component (A) and the diazomethane acid generator are combined, the LER can be further lowered to obtain good resolution. The amount of the diazo-methyl-based acid generator in the component (B) is preferably 40 to 95% by mass', more preferably 50 to 9% by mass. -23- (§, (21) 1299435 (B) In addition to the above-mentioned diazomethane acid generator, the addition of a _ salt acid generator can enhance the sensitivity of the positive photoresist composition of the present invention. Further, it is preferable to improve the linearity of the mask (reticle reproducibility). (B) The amount of the key salt acid generator in the component is preferably 5 to 60 mass%, more preferably 10 to 50% by mass. When a diazomethane acid generator and a key salt generator are used in combination, the ratio of the two (diazomethane acid generator: key salt generator; mass ratio) Preferably, it is 9 ··1 to 1:9, more preferably 8:2 to 6: 4. Further, the total amount of the diazomethane acid generator and the key salt acid generator in the component (B) is preferably 80% by mass or more, preferably 100 mass%. (Β) The content of the component is 0.5 to 30 parts by mass, preferably 1 to 10 parts by mass, per 100 parts by mass of the (Α) component. It is feared that the pattern cannot be sufficiently formed, and when it exceeds the range, it is difficult to obtain a uniform solution, which may cause a decrease in storage stability. f · Organic solvent The positive resist composition of the present invention may be The above (Α) component, (Β) component, and any of the components described below are dissolved in an organic solvent. The organic solvent can be a compound which can dissolve the components used to form a homogeneous solution, so it is suitable for the prior chemical strengthening type. Any one or two or more kinds of known solvents for the photoresist, for example, 7-butyrolactone, acetone, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone, 2-heptanone Ketones; ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, propylene glycol monoacetate

-24- (22) 1299435, dipropylene glycol or dipropylene glycol monoacetate, one of methyl ether, monoethyl ether, monopropyl ether, monobutyl ether or monophenyl ether, and its derivatives Cyclic ethers such as dioxane; methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methoxypropionate Esters such as esters and ethyl ethoxypropionate. The organic solvent may be used singly or in combination of two or more.

Among them, at least one selected from the group consisting of propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monomethyl ether (PGME), and ethyl lactate (EL) is preferred. Further, a mixed solvent of propylene glycol monomethyl ether acetate (PGMEA) and a polar solvent is preferred. The addition is appropriately determined in consideration of the compatibility of the PGMEA and the polar solvent, but is preferably 9:1 to 1:9, more preferably 8:2 to 2:8. More specifically, when the polar solvent EL is added, the mass Φ of PGMEA: EL is preferably from 8:2 to 2:8, more preferably from 7:3 to 3:7. Other preferred organic solvents such as PGMEA and EL select at least one mixed solvent with r · butyrolactone. The mixing at this time is better, the mass ratio of the former to the latter is 70: 30 to 95: 5. The amount of the organic solvent to be used is not particularly limited, and the concentration of the substrate or the like can be appropriately set depending on the coating film thickness. Generally, the solid content concentration of the photoresist composition is 2 to 20% by mass, preferably 5 To 15 mass% -25- (23) 1299435 • Nitrogen-containing organic compound (C) (hereinafter also referred to as (C) component) The positive resist composition of the present invention is used to enhance the shape of the resist pattern and to place the warp. A nitrogen-containing organic compound (C) (hereinafter referred to as a (C) component) for adding any component may be added to the post exposure stability of the latent image formed by the pattern-wise exposure of the resist layer or the like. It is known that the (C) component has various proposals, so that the known compound can be used arbitrarily, but it is preferably an amine, particularly preferably a secondary aliphatic amine and a tertiary aliphatic amine. The lower aliphatic amine refers to an alkyl group having an alkyl group of 5 or less or an amine of an alkanol, and the amines of the second and third stages are, for example, trimethylamine, diethylamine, triethylamine, di-n-propylamine. Further, tri-n-propylamine, tripentylamine, diethanolamine, triethanolamine, triisopropanolamine or the like is particularly preferably a tertiary alkanolamine such as triethanolamine or triisopropanolamine. These amines may be used singly or in combination of two or more.

The amount of the component (C) used in 100 parts by mass of the (Α) component is generally from 0.01 to 5.0 parts by mass. • Acid component (D) (hereinafter also referred to as (D) component) In order to prevent the sensitivity of the (C) component from being deteriorated, and to improve the shape of the photoresist pattern, the post exposure stability of the latent An acid component (D) which may be formed by an organic carboxylic acid, an oxyacid of phosphorus or a derivative thereof, which may be contained in any other component (hereinafter referred to as (D) Cheng-26-8 (24) 1299435 copies). Further, the component (C) and the component (D) may be used alone or in combination with any of the hydrazines, organic carboxylic acids such as malonic acid, citric acid, malic acid, succinic acid, benzoic acid, salicylic acid and the like. Phosphorus oxyacid or its derivatives such as phosphoric acid, di-n-butyl phosphate, diphenyl phosphate and other derivatives of phosphoric acid and esters thereof; phosphonic acid, dimethyl phosphonate, phosphonic acid-two -phosphine acids such as η-butyl ester, phenylphosphonic acid, diphenyl phosphonate, dibenzyl phosphinate and derivatives thereof; phosphinic acid, phenylphosphinic acid and other hypophosphorous acid and A derivative of an ester, particularly preferably a phosphonic acid. The use ratio of the component (D) to the component (A) per 100 parts by mass is 〇·〇1 to 5.0 parts by mass. <Other optional components> The positive-type photoresist composition of the present invention may be added with a mixture of additives such as an additive resin for improving the properties of the photoresist film, a surface-enhancing agent for improving the coating property, and a plasticizer. , stabilizers, colorants, anti-halation agents, etc. Further, it may contain any additive which has at least one acid dissociable dissolution inhibiting group and which is capable of dissociating the dissolution inhibiting group by an acid generated by a ^(Β) component to obtain a compound (Ε) of an organic carboxylic acid. The (Ε) component is preferably a phenol derivative having a mass average molecular weight of 200 to 1, 〇 and having 1 to 6 substituted or unsubstituted benzene nuclei. Specific examples are the compounds represented by the following general formula (1). -27- (25) 1299435

(wherein R' is an acid dissociable dissolution inhibiting group).

Further, a known acid dissociable dissolution inhibiting group in a chemically strengthened positive type photoresist can be arbitrarily selected. Specific examples are preferably a tertiary alkoxycarbonyl group such as tert-butoxycarbonyl tert-pentyloxycarbonyl; a tertiary alkoxycarbonyl group such as tert-butoxycarbonylmethyl or tert-butoxycarbonylethyl; Alkyl; tert-butyl, tert-pentyl, etc. 3-alkyl; tetrahydropyranyl, tetrahydrofuranyl, etc.; cyclic fluorenyl; ethoxyethyl, methoxypropyl and the like. More preferably, it is tert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-butyl, tetrahydropyranyl, ethoxyethyl, methylcyclohexyl and 1-ethylcyclohexyl. However, at least one of the acid-dissociable dissolution inhibiting groups R' used is a 3-stage alkoxycarbonylalkyl-based carboxylic acid-generating group. The positive photoresist composition of the present invention can be used for forming a photoresist pattern with a positive photoresist composition for the prior KrF. The positive-type photoresist composition of the present invention can obtain a photoresist pattern having high squareness and excellent LER and resolution. This photoresist pattern has high practicability' and can improve the DOF and EL safety factor. It is presumed that the effect is due to the fact that the constituent unit (a2) containing a monocyclic or polycyclic group containing a lactone is hydrophilic, and contains a monocyclic or polycyclic group of lactones. 8-28-(26) 1299435 product If the alkali solubility is lower than the constituent unit (a 1), the copolymer formed by the constituent unit (a 1), the constituent unit (a2), and the constituent unit (a3) is more hydrophilic than only the constituent unit (a). 1) The polyhydroxystyrene formed can be a substance having low alkali solubility. Further, for example, the photoresist pattern obtained by the development step can be observed by SEM (Scanning Electron Microscope) to confirm the effect of the present invention for improving the resolution, the squareness, and the LER.

Next, a method of forming a photoresist pattern of the present invention will be explained. First, the positive-type photoresist composition of the present invention is applied onto a substrate such as a circuit board by a spin coater, and after pre-baking, an exposure apparatus or the like is used to align the coating film of the positive-type photoresist composition with a desired pattern. The cover is selectively exposed and then PEB (post-exposure heating). Thereafter, the development process is carried out using an alkali developing solution, and the cleaning treatment is performed to remove the developing liquid on the substrate and the photoresist composition dissolved in the developing liquid, followed by drying. All steps can be performed in a known manner. Further, the operating conditions and the like may be appropriately set depending on the composition and characteristics of the positive resist composition used. It is preferable to use a KrF plasma laser for exposure, but it is suitable for electron line photoresist and EUV (extreme ultraviolet light). Further, depending on the case, a heating step after alkali development may be included, or an organic or inorganic antireflection film may be provided between the substrate and the coating layer of the photoresist composition. The heating temperature during pre-baking and the heating temperature after exposure (PEB) are generally 90 ° C or higher, but in order to form a good rectangular photoresist pattern, each is preferably 90 to 120 ° C, preferably 90 to 1 10 ° C. Microbridge generation can be effectively suppressed in this temperature range. -29 - 8 (27) 1299435 [Embodiment] - Example The following "%" means "% by mass" unless otherwise noted. [Synthesis Example 1] <Precursor of synthetic copolymer (A1)> 24% of P-hydroxystyrene (hereinafter referred to as "PHS") and 43% of p-ethyl f-phenol were contained. 93 3 g of a mixed solution of methanol 23% and water 10% (hereinafter referred to as a monomer 1 solution) was placed in a vessel maintained with nitrogen. Further, 62 g of a mixed solution of PHS 2 4 %, p -ethylstyrene 4 3 %, methanol 2 3 %, and water 10% and MAIB (dimethyl 2-2' azobis(2-methyl group) were contained. Propionate)) 39 g was placed in another vessel maintained with nitrogen and dissolved to give an initiator solution. 252 g of 50% MEX (methyl ethyl ketone) solution of oxa-tricyclic fluorenone methacrylate (hereinafter referred to as OTM) and 5.9 g of TDM (tert-dodecyl decyl alcohol) were placed in another In a nitrogen container, the monomer 2 solution was obtained after mixing. Next, the monomer 1 solution in the polymerization tank of φ was 80 ° C was stirred, and the temperature was raised to 80 ° C, and the monomer 2 solution and the initiator solution were supplied at 4 hours. After the completion of the supply, the mixture was aged at a polymerization temperature of 80 ° C for 1 hour, and then cooled to room temperature. After the obtained polymerization liquid was dropped into 3,500 g of toluene to precipitate a polymer, the supernatant liquid was removed. Thereafter, the mixture was dissolved in 500 g of methanol three times, and reprecipitated with toluene of 3,500 g to remove the supernatant liquid. Then, it is dissolved in 100 g of methanol, and the obtained methanol solution is heated under reduced pressure to extract a low-boiling solvent such as methanol, and propylene glycol monomethyl etherate (hereinafter referred to as "PGMEA") is added to obtain a copolymer (precursor). 20% by mass of PGMEA solution, and said to be -30-8 (28) 1299435 Resin 1. The composition of the copolymer (precursor), the composition of Mw and Mw/Mn 〇 copolymer (precursor) were determined by nuclear magnetic resonance spectroscopy (13C-NMR) and GPC analysis using carbon 13 (mass 13 carbon). :PHS/OTM = 82.5/17.5 (mol%) Molecular weight (Mw): 73 00 Molecular weight distribution (Mw/Mn): 1.5 5 f [Synthesis Example 2] <Introduction of an acid dissociable dissolution inhibitory group into a precursor Aldehyde)> 25 g of the resin 1 solution obtained above was placed in a vessel maintained with nitrogen, and after heating to 40 ° C, 20% trifluoroacetic acid (hereinafter referred to as TFA) / PGMEA solution 1 · 5 g of stirring 1 was added. After 0 minutes, 17.8 g of a 50% ethyl vinyl ether (hereinafter referred to as EVE)/PGMEA solution was further added, and the reaction was carried out at 40 ° C for 6 hours. After the reaction is completed, it is cooled to room temperature and then ionized on the glass column.

The exchange resin (B20HG DRY made by Ocano) was passed through the liquid to remove TEA. The reaction solution was passed through a Zeota plus 40 QSH filter manufactured by Seiko Co., Ltd., and then concentrated under reduced pressure to obtain a PGM EA solution containing 30% by mass of the acetalized copolymer, which was referred to as Resin 2. The acetalization ratio, Mw and Mw/Mn of the solution were determined by 13 C-NMR and GPC analysis. Further, the acetalization ratio means a ratio of the acetal type acid dissociative dissolution inhibiting group 〇-ethoxy-1-ethyl group derived from ethyl vinyl ether in the hydroxyl group of the PHS unit of the precursor. The acetalization ratio is 3 3.8 %. The molecular weight Mw = 8,0 00 The molecular weight distribution Mw / Mn = 1.64 -31 - 5 (29) 1299435 The acetalization copolymer obtained in this synthesis example The substance (resin 2) is formed by three structural units represented by the following chemical formula (14). In the chemical formula, X: y ·· z (Mo Erbi) = 54·6 : 27.9 : 17·5 .

...(14)

[Synthesis Example 3] &lt;Introduction of an acid dissociable dissolution inhibiting group into a precursor (acetalization)&gt; In addition to the addition of the EVE/PGMEA solution of Synthesis Example 2 to 12.2 g, and the reaction after adding the EVE/PGMEA solution The time was changed to 5 hours, and other PGMEA solution of the total acetalized copolymer of 30% by mass was obtained as the resin 3. The awakening ratio, Mw and Mw/Mn of the solution were determined by 13 C-NMR and GPC analysis. The acetalization rate was 22.9% and the molecular weight Mw was 7860. Molecular weight distribution Mw / Mn = 1.60 The acetalized copolymer (resin 3) obtained in the synthesis example is formed by three structural units represented by the above formula (14). In the chemical formula X: y ·· z (Mo Erbi) = 63.6 : 18.9 : 17·5 . <Example 1> -32- (30) 1299435 Resin 2 obtained in Synthesis Example 2 and Resin 3 obtained in Synthesis Example 3 were used as the component (A) to prepare a positive resist composition. 100 parts by mass of the component (A) (resin 2: resin 3 = 5:5) and (B) are used in an amount of 10 parts by mass of the compound represented by the following chemical formula (2), and 4.0 parts by mass of the compound represented by the following chemical formula (3). 4.0 parts by mass of the compound represented by the following chemical formula (4), 0.3 parts by mass of the compound represented by the following chemical formula (5), and 0.28 parts by mass of the component (C), 0.28 parts by mass of triisopropanolamine, and (E) In a portion of the compound represented by the following chemical formula (6), 2 parts by mass of a fluorine-based surfactant (product name XR-104, manufactured by Dainippon Ink and Chemicals Co., Ltd.), 0.025 parts by mass, dissolved in a mixed solvent of PGMEA and EL (PGMEA: EL) In the mass ratio of 6:4), a positive resist composition (solid content concentration of 10% by mass) was obtained.

8 (31)1299435 H3C-C — N-OS〇2—n—C4H9 H3C-0== N-OS〇2一 n-· · · (5)

The material for an organic anti-reflection film (trade name: DUV-44, manufactured by Preuwa Co., Ltd.) was applied onto an 8-inch ruthenium circuit board, and fired at 22 5 t for 60 seconds to obtain an anti-reflection film having a film thickness of 65 nm. Substrate. The obtained positive resist composition was uniformly applied onto the substrate by a spin coater, prebaked at 100 ° C for 60 seconds on a hot plate, and dried to form a photoresist layer having a film thickness of 2 87 nm.

Next, a KrF exposure apparatus (wavelength 248 nm) NSR-S203 B (manufactured by Nikon Corporation, NA (number of openings) = 0.68, 2/3 wheel belt illumination) was used, and an optional exposure of 8% half-degree linear mask was used. Thereafter, the PEB treatment was carried out under the conditions of ll 〇 ° C for 60 seconds, and the image was incubated with a 2.38 mass % tetramethylammonium hydroxide aqueous solution at 23 ° C for 60 seconds, followed by washing with pure water for 30 seconds, and drying. After heating at 100 ° C for 60 seconds, it is dried to form a 120 ° line and space (1:1) photoresist pattern (hereinafter referred to as l/s pattern). The substrate on which the L/S pattern was formed was observed using a scanning electron microscope (length measuring SEM, S-9200) manufactured by Hitachi, Ltd., and the profile of the L/S pattern was obtained.

-34- (32) 1299435 It is a good thing without high rectangularity. The formed pattern is obtained as 3σ of the LERR degree. As a result, the 3 σ of the pattern obtained was 3.4 nm. The 3 σ is 3 times 标准 (3σ) of the standard deviation (σ) calculated by the side length SEM (manufactured by Hitachi, Ltd., trade name "S-9220"). The smaller the 3σ, the smaller the roughness, the more uniform the photoresist pattern. The depth of focus (DOF) is 0.5gm.

The exposure safety factor (EL safety factor) obtained in the range of ±10% of the 120 nmL/S pattern was 14.79%. (Comparative Example 1) The positive light of the same Example 1 was used except that the resin Y protected by the 1-ethoxyethyl group of 42 mol% of the hydroxyl group of polyhydroxystyrene (Mw 8,000) was used as the component (A). Blocking composition. A photoresist pattern is formed using the positive photoresist composition. This resin Y is a copolymer formed of two constituent units represented by the following chemical formulas. Chemical formula. Medium X: y (Morby) = 58: 42.

The substrate forming the L/S pattern was evaluated in the same manner as in Example 1, and as a result, an L/S_ type of 120 - 35 - 1299435 (33) nm was formed, but the tip of the pattern was rounded. The LER is 3 σ = 5·5ηΐΏ ’ the depth of focus is 〇·2μηι, and the exposure safety factor is 7.73%. From the above, it was found that Example 1 can obtain a better resistive pattern rectangularity than Comparative Example 1, and can reduce the LER to obtain a fine photoresist pattern. In addition, the depth of focus and the exposure safety factor can be improved.

Claims (1)

1299435 (1) X. Patent application scope 1 · A positive-type photoresist composition characterized by containing a resin component (A) which can increase alkali solubility under acid action, and an acid generator component which can produce acid under exposure ( In the positive resist composition of B), the resin component (A) contains a constituent unit (al) having a phenolic hydroxyl group, a constituent unit (a2) containing a lactone-containing monocyclic or polycyclic group, and an acid group. The copolymer (A1) of the constituent unit (a3) of the dissociative dissolution inhibiting group. 2. The positive resist composition according to item 1 of the patent application, wherein the constituent unit (al) is a constituent unit (al-l) represented by the following general formula (I), (wherein R is a hydrogen atom or a methyl group) The constituent unit (a2) is a constituent unit (a2-l) represented by the following general formula (π), (wherein R is a hydrogen atom or a methyl group, and X is a lactone-containing monocyclic or polycyclic group). The constituent unit (a3) is a constituent unit (ahi) represented by the following general formula (111), -37- (2) ) 1299435 (wherein 'R is a hydrogen atom or a methyl group, and Y is an acid dissociable dissolution inhibiting group). m 3 · A positive photoresist composition as claimed in claim 1 The W unit (a2) is a constituent unit (a2-l 1) represented by the following general formula (IV), (wherein R is a hydrogen atom or a methyl group, and m is hydrazine or 1) The following structural unit (a2-12) R is represented by the general formula (V) -38- (3) 1299435 (wherein R is a hydrogen atom or a methyl group) The following general formula (VI) shows the constituent unit (a2-l 3) (wherein R is a hydrogen atom or a methyl group) and the following general formula (VII) does not constitute a unit (a2-l4) (wherein R is a hydrogen atom or a methyl group) at least one selected from the group. 4. The positive resist composition of claim 1, wherein the ratio of the constituent units (a3) of the constituent units (al) and (a3) is 5 to 50 mol%. -39- (4) 1299435 5. The positive-type photoresist composition of claim 1, wherein the ratio of constituent units (a2) in the copolymer (A1) is 5 to 50 mol%. 6. The positive-type photoresist composition according to claim 1, wherein the acid-dissociable dissolution inhibiting group of the constituent unit (a3) is an alkoxyalkyl group. A 7 The positive resist composition of claim 1, wherein the acid generator component (B) contains a diazomethane acid generator. 8. The positive-type photoresist composition according to item 7 of the patent application, wherein the acid generator component (B) further contains an iron salt-based acid generator. 9 • A positive-type photoresist composition as claimed in claim 1 which additionally contains a nitrogen-containing organic compound (C). 1 0 · A method for forming a photoresist pattern, characterized in that the positive-type photoresist film is selected after forming a positive-type photoresist film on the substrate using a positive-type photoresist composition as in claim 1 The exposure treatment is followed by development processing to form a photoresist pattern. -40 5