JP2014197195A - Pattern formation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of forming a regular pattern with reduced variation by utilizing a self-organizing micro phase separation structure.SOLUTION: A method of forming a regular pattern includes a step of forming, on a substrate, a bond with a first bonding group of a first hydrophilic homopolymer and a second bonding group of a second hydrophobic homopolymer which is cleavable with acid, base, light or heat to form a block copolymer consisting of the first homopolymer and the second homopolymer bonded together, a step of causing the formed block copolymer by a heat treatment to undergo micro phase separation so as to arrange alternately the hydrophilic region containing the first homopolymer and the hydrophobic region containing the second homopolymer and a step of cleaving the bond between the first homopolymer and the second homopolymer selectively by acid, base, light or heat.

Description

  The present invention relates to a pattern forming method.

  Miniaturization of semiconductor devices and the like has been achieved by using an exposure light source having a shorter wavelength in lithography. As a method for obtaining fine patterns at a lower cost and higher throughput, a self-assembly method (AASA: Artificially Assisted Self-Assembling) that controls the pattern arrangement using the phase separation phenomenon of block copolymers has been proposed (for example, , See Patent Document 1).

  A method for producing a recording medium using the obtained polymer pattern has also been proposed (see, for example, Patent Document 2). Although the polymer pattern is used as an etching mask, it becomes difficult to obtain a structure faithfully corresponding to the phase separation structure when the pattern size is reduced. Due to the generated variation, the regularity of the pattern after processing is lowered. Since dyeing and dry etching steps are required, the number of process steps and cost increase.

U. S. Patent 5,948,470 JP 2002-279616 A

  An object of the present invention is to provide a method of forming a regular pattern with small variations by using a self-organized microphase separation structure.

  The pattern forming method according to one embodiment of the present invention includes an acid, a base, light, or a hydrophilic first homopolymer binding group and a hydrophobic second homopolymer second binding group. A bond capable of being cut by heat is formed on a substrate to form a block copolymer in which the first homopolymer and the second homopolymer are bonded; and the formed block copolymer is subjected to heat treatment to form a microphase. Separating the hydrophilic region containing the first homopolymer and the hydrophobic region containing the second homopolymer, and the first homopolymer and the second homopolymer And the step of selectively cleaving the bond with an acid, a base, light or heat.

  According to the present invention, it is possible to form a regular pattern with small variations using a self-organized microphase separation structure.

The phase diagram which shows the state of micro phase separation. The schematic diagram which shows the coupling | bonding of a 1st polymer chain and a 2nd polymer chain. Sectional drawing which shows 1 process of the pattern formation method which concerns on one Embodiment. Sectional drawing which shows the process of following FIG. FIG. 5 is an enlarged cross-sectional view illustrating a process following FIG. 4. Sectional drawing which shows the process of following FIG. Sectional drawing which shows the process of following FIG. Sectional drawing which shows the process of following FIG. Sectional drawing which shows the process of following FIG. Sectional drawing which shows the other process following FIG. FIG. 11 is a cross-sectional view showing a step following FIG. 10. Sectional drawing which shows the process following FIG. Sectional drawing which shows the process following FIG. Sectional drawing which shows the process of following FIG.

  Embodiments of the present invention will be described below.

When two or more types of homopolymers are mixed, it is rare that a uniform mixed state is obtained. As a result of repulsion between different homopolymers, homopolymers of the same type aggregate to cause phase separation. Even in block copolymers, chemically linked heterogeneous polymers repel and phase separation occurs. Because different homopolymers are chemically bonded in the molecule, the phase size cannot be increased. The size of the phase is about the same as the rotation free radius R _g of the block copolymer. Such phase separation of the block copolymer is microphase separation, and a phase separated at a pitch of several nm to 100 nm is formed.

  The shape of the microphase-separated domain greatly depends on the degree of polymerization of the block copolymer, the chemical properties of each block chain, the volume fraction of each block chain, and the like. The microphase separation of the diblock copolymer will be described with reference to FIG.

  In FIG. 1, the horizontal axis represents the volume fraction f of the first polymer chain, and the vertical axis represents the product χN of the interaction parameter χ and the degree of polymerization N of the first and second polymer chains. The larger the value of χ, the lower the compatibility of the polymers with each other and the easier the phase separation. Further, the greater the degree of polymerization N, the easier the phase separation. Therefore, χN is often used as an index of ease of phase separation, and phase separation is easier as the value of χN increases. On the other hand, if the value of χN becomes too small, phase separation cannot be shown, and the state becomes disordered. Generally, it is known that when the value of χN is 10 or less, a disordered state occurs.

Regarding the phase separation pitch L _0, there is a relation of L _{0 to} aN ^2/3 χ ^1/6 . S. Bates et al .; Annu. Rev. Phys. Chem. , Vol. 41, p. 525-557. The pattern size is defined by the length a of the segments forming the polymer, the degree of polymerization N of the block copolymer, and the χ parameter. A fine pattern can be obtained by changing the degree of polymerization and the type of polymer as long as the phase separation of the block copolymer occurs stably.

In the embodiment of the present invention, a polymer that exhibits a microphase separation structure is based on a structure in which a first polymer chain 21 and a second polymer chain 22 are bonded as shown in FIG. The bond 23 between the first polymer chain 21 and the second polymer chain 22 includes a part of the first binding group at the end of the first polymer chain 21 and the second bond at the end of the second polymer chain 22. And a part of the bonding group is formed by bonding. A bond between a part of the bonding groups is formed by, for example, dehydration condensation, S _N 2 reaction, or the like.

  The bond 23 formed needs to be cleavable by acid, base, light or heat. Examples of the bond include an acetal bond formed by a reaction of a carbonyl group and an alcohol or a diol, an ether bond formed by a reaction of a hydroxyl group and methoxymethyl ether chloride, a hydroxyl group and trimethylsilyl chloride or triethylsilyl chloride. Examples thereof include a silyl ether bond formed by a reaction, an ester bond formed by a reaction between a carboxyl group and an alcohol, and an amide bond formed by a reaction between an amino group and a carboxyl group. Such bonds can be cleaved by acid.

  Examples of the bond cleaved by the base include an ester bond formed by a reaction between a hydroxyl group and acetic anhydride or benzoyl chloride.

  A combination of the first and second linking groups is selected such that the desired linkage is obtained, and each linking group is combined with an appropriate polymer chain to produce the first homopolymer and the second A homopolymer can be prepared.

  The combination of the first polymer chain and the second polymer chain can be selected as follows. In two types of polymer chains, it is known that the square of the solubility parameter difference affects the interaction parameter χ between these polymers. Therefore, what is necessary is just to combine a 1st polymer chain and a 2nd polymer chain so that the difference of the solubility parameter according to desired pattern size may be obtained. It is also necessary to set the polymerization degree and segment length of the polymer chain according to the desired pattern size. However, in order to form a pattern, a difference in solubility is required between the first homopolymer and the second homopolymer.

  In one embodiment, the first homopolymer is hydrophilic and the second homopolymer is hydrophobic. As long as this condition is satisfied, the combination of the binding group and the polymer chain is not particularly limited.

  As the polymer chain, for example, a polydiene derivative polymer chain, a polyalkene derivative polymer chain, a polyacrylate derivative polymer chain, a polymethacrylate derivative polymer chain, a polystyrene derivative polymer chain, and a polysiloxane chain can be used.

  Specific examples of the polydiene derivative polymer chain include poly (1,2-butadiene), poly (1,3-butadiene), poly (chloroprene), poly (1,4-cis-isoprene), and poly (isobutylene). ) And the like.

  Specific examples of the polyalkene derivative polymer chain include poly (ethylene), poly (isobutene), poly (propylene), and poly (2-methylpropene).

  Examples of polyacrylic acid ester derivative polymer chains include poly (methyl acrylate), poly (ethyl acrylate), poly (t-butyl acrylate), poly (n-butyl acrylate), poly (neopentyl acrylate), poly (n -Nonyl acrylate), poly (n-octyl acrylate), poly (2-ethylhexyl acrylate), poly (1-ethoxyethyl acrylate), poly (hydroxyethyl acrylate) and the like.

  Specific examples of polymethacrylate derivative polymer chains include poly (methyl methacrylate), poly (ethyl methacrylate), poly (n-propyl methacrylate), poly (n-butyl methacrylate), and poly (t-butyl methacrylate). , Poly (neopentyl methacrylate), poly (cyclohexyl methacrylate), poly (2-hydroxyethyl methacrylate), poly (2-hydroxypropyl methacrylate), poly (trifluoroethyl methacrylate) and the like.

  Specific examples of the polystyrene derivative polymer chain include polystyrene, poly (α-methylstyrene), poly (2-vinylpyridine), poly (4-vinylpyridine), poly (4-hydroxystyrene), and poly (t- Butyl styrene), poly (t-butoxy styrene), poly (4-aminomethyl styrene), poly (4-methyoxy styrene), poly (p-chloromethyl styrene) and the like.

  Specific examples of the polysiloxane chain include poly (dimethylsiloxane), poly (diphenylsiloxane), and poly (methylphenylsiloxane).

  Furthermore, poly (ferrocenyldimethylsilane), polyacrylonitrile, polyacrylamide, poly (N, N-dimethylacrylamide), poly (vinyl alcohol), poly (4-vinylphenol), poly (vinyl acetate), poly (vinyl) Chloride), poly (vinyl bromide), poly (tetrafluoroethylene), poly (ε-caprolactone), poly (ethylene oxide), poly (propylene oxide), polyacrylic acid, and polymethacrylic acid.

  Examples of hydrophilic polymer chains include polyethylene oxide, polymethyl methacrylate, polyvinyl alcohol, polyacrylonitrile, and polypropylene, and examples of hydrophobic polymer chains include polystyrene, polyethylene, polyisoprene, and polydimethyl. Examples thereof include siloxane.

  The weight average molecular weight of the first and second homopolymers is not particularly limited, but is preferably 1000 to 200000. The volume ratio can be selected according to the intended phase separation morphology based on the phase diagram of the volume ratio and the molecular weight as shown in FIG.

  The first homopolymer and the second homopolymer are dissolved in a solvent to obtain a blend polymer solution. What is necessary is just to select suitably the compounding ratio of a 1st homopolymer and a 2nd homopolymer according to the structure of a target phase-separation, a pitch, etc. For example, the weight ratio can be about 20:80 to 40:60. As the solvent, water, alcohol solvents, ester solvents, ketone solvents, cellosolve solvents, ether solvents, aromatic solvents, and the like can be used.

  Examples of the alcohol solvent include methanol, ethanol, and 2-propanol. Examples of the ester solvent include ethyl acetate, ethyl lactate, butyl acetate, isoamyl acetate, γ-butyrolactone, and 3-methoxypropionic acid. Examples include methyl and diethyl carbonate.

  Examples of ketone solvents include cyclopentanone, cyclohexanone, acetone, methyl ethyl ketone, and methyl isobutyl ketone. Examples of cellsolv solvents include methyl cellosolve, methyl cellosolve acetate, ethyl cellosolve acetate, and butyl cellosolve acetate. .

  Examples of the ether solvent include diethylene glycol dimethyl ether and ethylene glycol monomethyl ether, and examples of the aromatic solvent include toluene, xylene, anisole, tetralin, and tetramethylbenzene.

  Furthermore, propylene glycol monoethyl acetate (PGMEA) or the like can be used.

  The above-described solvents can be used alone or as a mixed solvent of two or more. The solvent may be appropriately selected so that the blend polymer containing the first homopolymer and the second homopolymer dissolves well. The concentration of the polymer in the solution is selected according to the coating conditions, but is generally about 1 to 10% by weight.

The blend polymer solution is applied onto the substrate 31 as shown in FIG. The material of the board | substrate 31 is not specifically limited, A metal, a semiconductor, or an insulator can be used. The substrate 31 is preferably a Si substrate in which a flat region exists. It is desirable to provide an underlayer 32 between the substrate 31 and the coating film 33. The underlayer 32 has a function of promoting the vertical alignment of the polymer in the coating film 33 and is called a neutral film. The underlayer 32 can be formed by treating the substrate surface with a polymer having a hydroxyl group at the terminal.

  Since the Si substrate has a natural oxide film on the surface, hydroxyl groups exist on the surface of the substrate 31. The hydroxyl group on the substrate surface and the hydroxyl group at the polymer terminal in the underlayer 32 are bonded by dehydration condensation. The polymer used for forming the underlayer 32 is preferably in a state having a surface energy intermediate to that of the polymer constituting the diblock copolymer in the coating film 33 provided thereon. This is to ensure the vertical alignment of the predetermined polymer chain.

  What is necessary is just to select the polymer used for formation of the base layer 32 suitably according to the kind of diblock copolymer. For example, in the case of a diblock copolymer containing polystyrene and polyethylene oxide, the underlayer 32 can be formed using a random copolymer of polystyrene and polymethyl methacrylate. A predetermined polymer is dissolved in a solvent such as toluene to prepare a solution of about 1% by weight. This solution is applied to the substrate 31 and heated at 140 ° C. to dehydrate and condense the substrate surface and the polymer. Thereafter, the base layer 32 is formed on the surface of the substrate 31 by removing unreacted polymer by washing with toluene. By performing such treatment, it can be said that the surface of the substrate 31 is modified.

  In forming the coating film 33 on the underlayer 32, the blend polymer solution can be applied by any method. In general, methods such as spin coating, roller coating, dip coating, brush coating, spray coating, and curtain coating can be used. A spin coating method is preferable because a film having excellent uniformity can be obtained.

  By heating the coating film of the blend polymer, a part of the first binding group at the end of the first homopolymer is bonded to a part of the second binding group at the end of the second homopolymer. To do. Furthermore, microphase separation of the block copolymer comprising the first homopolymer and the second homopolymer occurs, facilitating the cylindrical arrangement. The heat treatment temperature here is higher than the glass transition temperature of the constituent polymer and lower than the melting point of the constituent polymer. Generally, heat treatment is performed at a temperature within the range of 100 to 300 ° C. The temperature T2 that satisfies the following relationship can be set as the heat treatment temperature.

T1 <T2 <T3
(T1 is a temperature at which the first binding group and the second binding group are bonded, and T3 is a temperature at which the bond is thermally broken.)
The time for the heat treatment is the time at which the reaction in which a part of the first binding group at the end of the first homopolymer and the part of the second binding group at the end of the second homopolymer are combined is completed, Although it can be suitably determined according to the time for optimizing the phase separation structure, it is usually about 12 to 36 hours. When solvent annealing is performed, a pattern with a large area and few defects can be produced.

  In some cases, by mixing, a part of the binding group at the end of the first homopolymer and a part of the binding group at the end of the second homopolymer are bonded. When a bonding group having a high temperature at which a bond is formed is selected, it is desirable to perform heat treatment.

  In the coating film 32 after the heat treatment, as a result of the microphase separation, as shown in FIG. 4, the hydrophilic region 34 containing the first homopolymer and the hydrophobic region 35 containing the second homopolymer are alternately arranged. Adjacent to each other. A bond 36 is formed between the first homopolymer constituting the hydrophilic region 34 and the second homopolymer constituting the hydrophobic region 35. As described above, the bond 36 includes a part of the first binding group at the end of the first homopolymer and a part of the second binding group at the end of the second homopolymer. This is what happened.

  The bond formed between the first homopolymer and the second homopolymer is cleaved as shown in FIG. 5 by applying a predetermined stimulus. In FIG. 5, reference numeral 37 represents a broken bond. Examples of the stimulus include acid, base, light, and heat, and the bond is selectively cut at the phase separation interface.

  For example, in the case of a bond cleaved by acid, tris (4-methylphenyl) sulfonium trifluoromethanesulfonate, tris (4-methylphenyl) sulfonium hexafluorophosphate, and bis (4-tertbutylphenyl) iodonium trifluoromethanesulfonate A photoacid generator such as is added to the solution of the blend polymer. Thereby, an acid is generated by light irradiation, and the bond can be broken.

  Such a photoacid generator can be referred to as a cleavage initiator. If the cleavage initiator is blended in an amount of about 20 to 60% of the total weight of the first homopolymer and the second homopolymer, the effect is obtained.

  It is also possible to break the bond by directly dropping an acid or base solution onto the polymer film after microphase separation. It is preferable that the solution to be used is selectively immersed in a region to be dissolved and removed by subsequent solvent washing. As a result, a polymer pattern having a more precise shape can be obtained.

  After cutting the bond, the polymer pattern is formed by solvent washing as shown in FIG. 6 with a solvent that selectively dissolves one homopolymer region. The solvent used here is not particularly limited, and a solvent capable of satisfactorily dissolving and removing the target region can be appropriately selected depending on the polymer.

  It is preferable to adjust the surface free energy of the surface of the underlayer 32 in accordance with the hydrophilicity and hydrophobicity of the homopolymer to remain. This can prevent pattern collapse during solvent cleaning. The surface free energy is generally adjusted using a silane coupling agent. Examples of the silane coupling agent include compounds having a halogen group, an alkoxy group, or a silazane group at the terminal.

  In the pattern forming method of this embodiment, the first homopolymer and the second homopolymer are bonded to obtain a phase separation structure, and then the bond at the phase separation interface is broken. Next, the region containing any one of the homopolymers is dissolved and removed with a solvent to form a polymer pattern. Variation in the phase separation interface becomes the roughness of the obtained polymer pattern, and a regular pattern with small variation can be formed.

  Thus, a polymer pattern is obtained by dissolving and removing either the hydrophilic region or the hydrophobic region in the polymer film. When a polymer pattern is formed by dry etching, an etching residue may be generated due to local variation in etching rate. In the method of this embodiment, the polymer pattern is formed by dissolving and removing with a solvent, so that such a problem is avoided.

  Since the vacuum process and the dyeing process called dry etching can be omitted, it is possible to form a highly regularly arranged pattern with high accuracy and high throughput by the method of this embodiment.

  In the formed polymer pattern, since the binding groups are aligned on the surface, the wettability of the surface with respect to the solvent is good. The solvent used for solvent washing is not limited, and a wide range of solvents can be used. Moreover, since the molecular weight of the polymer to be eluted is almost uniform, the solubility in the solvent is constant. Thereby, it is also possible to reduce dissolution residues.

  Since a polymer pattern is formed by dissolving and removing a predetermined region with a solvent, the surface of the obtained polymer pattern is subjected to a hydrophilic treatment with the solvent. Even when fine dust such as particles adheres to the surface, it can be easily removed by washing with water.

Using the remaining polymer pattern as a mask, the base layer 32 is processed as shown in FIG. For example, when the underlayer 32 is made of a random copolymer of polystyrene and polymethyl methacrylate, etching is performed by reactive ion etching (RIE) using an etching gas such as O ₂ gas or CF ₄ gas.

Using the processed underlayer 32 and polymer pattern as an etching mask, the substrate 31 is processed as shown in FIG. For example, when the substrate to be processed is a silicon substrate, etching is performed by RIE using a fluorine-based etching gas such as CF ₄ . As a result, the exposed silicon substrate surface is etched, and the regular pattern is transferred.

  After the pattern is transferred to the substrate surface, the substrate is washed with a solvent that dissolves the underlayer 32 well, and the etching mask is peeled off as shown in FIG. Also in this case, the solvent to be used is not particularly limited, and a solvent capable of satisfactorily dissolving and removing the underlayer can be appropriately selected according to the material of the underlayer.

  When the polymer pattern left on the underlayer 32 does not have sufficient etching resistance, an inverted pattern can be formed to serve as an etching mask. Specifically, as shown in FIG. 10, the difficult-to-etch region 38 is formed of a material having high etching resistance. Examples of the material having high etching resistance include SOG (spin on glass). SOG is excellent in oxygen plasma etching resistance.

  Oxygen plasma treatment is performed to selectively remove the polymer pattern and expose the underlying layer 32 as shown in FIG. Using the difficult etching region 38 as an etching mask, the base layer 32 is processed by etching as shown in FIG. 12, and using the processed base layer 32 and the hard etching region 38 as a mask, a substrate as shown in FIG. 31 is processed by etching. The etching gas used in each processing step may be appropriately selected according to the object to be processed.

  After the pattern is transferred to the substrate surface, the substrate is washed with a solvent that dissolves the hardly-etched region well, and the difficult-to-etch region 38 is peeled off together with the base layer 32 as shown in FIG. As described above, the solvent used here is not particularly limited, and a solvent that can dissolve the underlayer satisfactorily can be appropriately selected according to the material of the underlayer.

  According to the pattern formation method of the present embodiment, the edge roughness and variation of the produced polymer pattern are small. For this reason, for example, when applied to the manufacture of patterned media, high-precision positioning is possible when positioning the recording / playback head to the pattern. When applied to high-density recording media and highly integrated electronic components, the number of substantial steps can be reduced, and the industrial advantage is tremendous.

  Hereinafter, although an Example is shown and it demonstrates in detail about embodiment of this invention, this invention is not limited to these Examples.

Example 1
A compound represented by the following chemical formula (1) was prepared as the first homopolymer, and a compound represented by the following chemical formula (2) was prepared as the second homopolymer.

  In the above chemical formula, n is the degree of polymerization of polystyrene, and m is the degree of polymerization of polyethylene oxide. As shown in the chemical formula, the first homopolymer is polystyrene having a carbonyl group at the end as a binding group, and the weight average molecular weight is about 20,000. The second homopolymer is polyethylene oxide having a diol at the terminal as a binding group, and the weight average molecular weight is about 11,000.

  The first homopolymer and the second homopolymer were mixed in a 1: 1 weight ratio. Furthermore, tris (4-methylphenyl) sulfonium trifluoromethanesulfonate was added as a photoacid generator. The amount of the photoacid generator added was about 50% of the weight of the polystyrene having a carbonyl group at the end. 1,4-Dioxane and water were mixed at a volume ratio of 1: 1 to prepare a mixed solvent, and the above mixture was dissolved to obtain a blend polymer solution. The concentration of the polymer in the solution was about 1% by weight.

  At this stage, the carboxyl group in the first homopolymer and the diol in the second homopolymer are dehydrated and condensed to form an acetal. The block polymer thus obtained is represented by the following chemical formula.

  The blend polymer solution was applied onto a silicon substrate by spin coating to form a coating film. Prior to coating, the surface of the silicon substrate was modified by the above-described method using a random copolymer of polystyrene-polymethyl methacrylate (polystyrene 25% -polymethyl methacrylate 75%). This ensures a vertical array of diblock polymers.

  After the application, heat treatment was performed at 180 ° C. for about 3 hours to form a microphase separation structure in the polymer film. Thereafter, light irradiation was performed using a low-pressure mercury UV lamp as a light source. An acid was generated from the photoacid generator, and the bond by the acetal connecting the first polymer chain and the second polymer chain was broken.

  By washing the polymer film after the light irradiation with water, the polyethylene oxide region was selectively dissolved and removed, and the polystyrene region arranged perpendicular to the substrate remained to form a polymer pattern.

  For evaluation of edge roughness, the dot diameter variation of this polymer pattern was evaluated by the half width at half maximum of the distribution of TEM measurement, and was about 7%.

  For comparison, a polymer pattern was formed in the same manner as described above except that a 65:35 copolymer of polystyrene and polyethylene oxide was used. The weight average molecular weight of the copolymer used here is about 30,000. The resulting polymer pattern had a dot diameter variation of as much as 10%.

  In Example 1, it was confirmed that the regularity of the regular arrangement pattern was improved.

  In the manufacture of electronic elements and storage media, the fact that the regular structure is not constant is often a big problem. For example, when considering application to the above-described patterned media, it is possible to cause recording noise with a high signal-to-noise ratio due to jitter noise in the reproduction signal and deviation from the positioning mark.

(Example 2)
Using a polymer pattern formed in the same manner as in Example 1 described above as a template, a magnetic patterned medium was produced.

  A CoCrPt alloy thin film having a thickness of 5 nm was formed on a glass substrate by sputter deposition. A polymer pattern made of polystyrene was formed on the obtained alloy thin film by the same method as in Example 1 described above. Between polymer patterns, spin-on glass (SOG) was filled to form difficult-to-etch regions.

  Oxygen plasma treatment was performed to selectively remove the polymer pattern made of polystyrene, leaving a hard-to-etch region made of SOG. Argon ion milling was performed using this difficult etching region as a mask. By etching the CoCrPt film in this way, the pattern was transferred to produce a patterned media.

  The variation in the formed dot diameter was about 8% of the dot diameter, and it was confirmed that a highly accurate regular array was formed even after substrate processing.

(Example 3)
A compound represented by the following chemical formula (4) was prepared as the first homopolymer, and a compound represented by the following chemical formula (5) was prepared as the second homopolymer.

  In the above chemical formula, k is the degree of polymerization of polystyrene, and j is the degree of polymerization of polyethylene oxide. As shown in the chemical formula, the first homopolymer is polystyrene having a hydroxyl group at the terminal as a binding group, and the weight average molecular weight is about 20,000. The second homopolymer is polyethylene oxide having a Br atom at the end as a binding group, and the weight average molecular weight is about 11,000. Halogen atoms other than Br atoms can also be introduced at the terminal of the second homopolymer as bonding groups.

  The first homopolymer and the second homopolymer were mixed in a 1: 1 weight ratio. Furthermore, tris (4-methylphenyl) sulfonium trifluoromethanesulfonate was added as a photoacid generator. The amount of the photoacid generator added was about 50% of the weight of the polystyrene having a hydroxyl group at the end. 1,4-Dioxane and water were mixed at a volume ratio of 1: 1 to prepare a mixed solvent, and the above mixture was dissolved to obtain a blend polymer solution. The concentration of the polymer in the solution was about 1% by weight.

At this stage, the hydroxyl group in the first homopolymer and the Br atom in the second homopolymer undergo an S _N 2 reaction due to the nucleophilic reaction by the hydroxyl group to form an ether bond. The block polymer thus obtained is represented by the following chemical formula.

  The blend polymer solution was applied onto a silicon substrate by spin coating to form a coating film. Prior to coating, the surface of the silicon substrate was modified by the above-described method using a random copolymer of polystyrene and polymethyl methacrylate. This ensures a vertical array of diblock polymers.

  After coating, heat treatment was performed at 180 ° C. for about 24 hours to form a microphase separation structure in the polymer film. Thereafter, light irradiation was performed using a low-pressure mercury UV lamp as a light source. An acid was generated from the photoacid generator, and the ether bond connecting the first polymer chain and the second polymer chain was cleaved.

  By washing the polymer film after the light irradiation with water, the polyethylene oxide region was selectively dissolved and removed, and the polystyrene region arranged perpendicular to the substrate remained to form a polymer pattern.

  When the dot diameter variation of this polymer pattern was determined by the same method as in Example 1, it was about 7%.

Example 4
Using a polymer pattern formed in the same manner as in Example 3 described above as a template, a magnetic patterned medium was produced.

  A CoCrPt alloy thin film having a thickness of 5 nm was formed on a glass substrate by sputter deposition. A polymer pattern made of polystyrene was formed on the obtained alloy thin film by the same method as in Example 3 described above. Between polymer patterns, spin-on glass (SOG) was filled to form difficult-to-etch regions.

  Oxygen plasma treatment was performed to selectively remove the polymer pattern made of polystyrene, leaving a hard-to-etch region made of SOG. Argon ion milling was performed using this difficult etching region as a mask. By etching the CoCrPt film in this way, the pattern was transferred to produce a patterned media.

  The variation in the formed dot diameter was about 8% of the dot diameter, and it was confirmed that a highly accurate regular array was formed even after substrate processing.

  The present invention is expected as a method for forming a fine pattern with small roughness.

DESCRIPTION OF SYMBOLS 21 ... 1st polymer chain; 22 ... 2nd polymer chain; 23 ... Bond | bond 31 ... Substrate; 32 ... Underlayer; 33 ... Coating film containing blend polymer 34 ... Hydrophilic region; 35 ... Hydrophobic region; Bonding; 37 ... Broken bond 38 ... Difficult to etch region.

Claims (5)

A bond capable of being cleaved by an acid, a base, light or heat is formed on the substrate with the binding group of the hydrophilic first homopolymer and the second binding group of the hydrophobic second homopolymer; Forming a block copolymer in which the first homopolymer and the second homopolymer are combined;
Microphase-separating the formed block copolymer by heat treatment, and alternately arranging hydrophilic regions containing the first homopolymer and hydrophobic regions containing the second homopolymer;
A pattern forming method comprising: selectively cutting the bond between the first homopolymer and the second homopolymer with an acid, a base, light, or heat.   The pattern forming method according to claim 1, wherein the bond cleaved by the acid is an ether bond or an acetal bond. The pattern forming method according to claim 1, wherein the heat treatment is performed at a temperature T <b> 2 that satisfies the following relationship.
T1 <T2 <T3
(T1 is a temperature at which the first binding group and the second binding group are bonded, and T3 is a temperature at which the bond is thermally broken.)   The pattern forming method according to claim 1, further comprising a step of processing the substrate surface to form an underlayer before forming the block copolymer. After cutting the bond, selectively removing the hydrophilic region or the hydrophobic region to obtain a polymer pattern;
The pattern forming method according to claim 1, further comprising: etching the substrate using the polymer pattern.

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