JP2015050322A - Pattern formation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve the formation of a pattern in a state where limitation is relieved, using a vertical cylinder phase structure formed by a microphase separation.SOLUTION: In a pattern formation method, a plasma oxidized layer 102 is formed on a surface of a substrate 101; a block copolymer thin film 103 comprising a block copolymer is formed on the plasma oxidized layer 102, the block copolymer comprising a first block chain and a second block chain having surface free energies different with each other; the block copolymer thin film 103 is heated to induce a microphase separation; a plurality of columnar phase structures 104 comprising the first block chain are formed on the block copolymer thin film 103; and the block copolymer thin film 103 is immersed into a process liquid 105 comprising an ammonium fluoride aqueous solution to form a plurality of openings 106.

Description

  The present invention relates to a pattern forming method for forming a fine pattern by utilizing a microphase separation structure.

  Conventionally, an all-wet pattern forming method using a vertical cylinder phase structure utilizing a microphase separation structure of a block copolymer is known (see Non-Patent Document 1).

  The pattern forming method described above will be described. First, as shown in FIG. 4A, a silicon substrate 401 having a main surface plane orientation of (100) is prepared. Next, heat treatment is performed on the silicon substrate 401 in an oxygen atmosphere to form a thermally oxidized silicon layer 402 with a thickness of about 20 nm on the main surface of the silicon substrate 401 as shown in FIG. 4B. Next, the thermal silicon oxide layer 402 is thinned to a thickness of about 2 nm by etching using an aqueous hydrogen fluoride (HF) solution.

  Next, as shown in FIG. 4C, a block copolymer thin film 403 is formed on the thinned thermally oxidized silicon layer 402. For example, a block toluene thin film 403 is formed by preparing a mixed toluene solution of an amphiphilic side chain liquid crystal block copolymer and polyethylene glycol monomethyl ether (PEGME) and applying the solution by a spin coating method. To do. The amphiphilic side chain liquid crystal block copolymer is composed of, for example, polyethylene oxide (PEO) and poly (11- [4- (4-butylphenylazo) phenoxy] -undecyl methacrylate) (PMA (Az)). It is a block copolymer (PEO-b-PMA (Az)).

  Next, the block copolymer thin film 403 is subjected to heat treatment to induce microphase separation, thereby forming a vertical cylinder phase structure 404 inside the block copolymer thin film 403 as shown in FIG. 4D. In this structure, the PEO block chain forms part of the vertical cylinder phase structure 404, and the PMA (Az) block chain forms the peripheral part of the vertical cylinder phase structure 404. In this state, the PEGME molecule 441 segregates in the vertical cylinder phase structure 404 because of its high affinity with the PEO block chain.

Next, as shown in FIG. 4E, an ammonium fluoride (NH ₄ F) aqueous solution 405 that is an etching solution is applied to the silicon substrate 401 on which the block copolymer thin film 403 in a microphase-separated state is formed as described above. PEGME molecules 441 that are segregated in the vertical cylinder phase structure 404 are water-soluble. Therefore, instead of being dissolved from the vertical cylinder phase structure 404 into the NH ₄ F aqueous solution 405, the NH ₄ F aqueous solution 405 is used. NH ₄ F molecules, which are solutes of the above, penetrate into the vertical cylinder phase structure 404.

Eventually, when the NH ₄ F molecules that have penetrated into the vertical cylinder phase structure 404 reach just below the vertical cylinder phase structure 404, the thermal silicon oxide layer 402 is dissolved, and as shown in FIG. Then, an opening 406 is formed. In addition, a part of the reaction product 442 generated along with the dissolution of the thermal silicon oxide layer 402 described above diffuses from the vertical cylinder phase structure 404 into the NH ₄ F aqueous solution 405.

  In the etching described above, only the portion immediately below the vertical cylinder phase structure 404 of the thermally oxidized silicon layer 402 is dissolved. Therefore, the nanohole array formed by the openings 406 reflecting the arrangement structure of the vertical cylinder phase structure 404 is heated in the thermally oxidized silicon layer 402. A silicon oxide film is formed.

  Next, the silicon substrate 401 is immersed in a mixed solution of tetrahydrofuran and water, and the block copolymer thin film 403 is dissolved and removed. Next, when the silicon substrate 401 is immersed in a potassium hydroxide (KOH) aqueous solution that is an etching solution of silicon, the silicon substrate 401 exposed at the bottom portions of the plurality of openings 406 formed in the thermally oxidized silicon layer 402 is dissolved. . When the silicon substrate 401 is etched using a KOH aqueous solution, since the etching rate of the Si (111) surface is slow, anisotropic etching occurs, and as shown in FIG. 4G, 54.7 with respect to the Si (100) surface. Etching proceeds so that a Si (111) surface inclined at a degree appears.

  In Non-Patent Document 1, since the etching time of silicon is too long, the etching of silicon starts through a part of the openings 406 formed in the thermally oxidized silicon layer 402, and a structure as shown in FIG. 4G is obtained. Yes.

R. Watanabe, K. Kamata, and T. Iyoda, "Smart block copolymer masks with molecule-transport channels for total wet nanopatterning", Journal of Materials Chemistry, vol.18, pp.5482-5491, 2008.

However, the above-described technique has a problem that a pattern that can be formed is limited. For example, in the above-described technique, in etching using an NH ₄ F aqueous solution for transferring a vertical cylinder phase structure formed by microphase separation to a silicon oxide layer, the silicon oxide layer needs to be thinned to about 2 nm. is there. Since such a thin thermally oxidized silicon layer has low dry etching resistance, wet etching is used when etching silicon. For this reason, a high aspect ratio hole pattern cannot be formed on a silicon substrate. In the above-described anisotropic etching of silicon, the maximum aspect ratio is about 1.41 (tan 54.7 °). When the etching proceeds isotropically by wet etching, the aspect ratio is about 1.

  Further, since the etching solution flows under the mask made of silicon oxide and the etching proceeds not only in the depth direction but also in the lateral direction, when the etching time is lengthened, adjacent hole patterns become continuous. For this reason, etching must be stopped when adjacent hole patterns are not connected, and the maximum diameter of the hole pattern remains at the distance D between adjacent hole centers, and the maximum depth of the hole pattern is about 1.41D. Stay on.

  Further, when thermal silicon oxide is used, the substrate material to be processed is limited to silicon, and the pattern that can be formed is also limited in this respect.

  The present invention has been made in order to solve the above-described problems, and allows a pattern to be formed without much restriction by utilizing a vertical cylinder phase structure formed by microphase separation. For the purpose.

  The pattern forming method according to the present invention includes a first step of forming a transfer layer made of an organic material on a substrate, a second step of applying a coating glass material on the transfer layer to form an SOG layer, and an SOG. A third step of thinning the layer to a predetermined thickness, a fourth step of oxidizing the SOG layer by applying oxygen plasma to the thinned SOG layer to form a plasma oxide layer, and a plasma oxide layer, A fifth step of forming a block copolymer thin film comprising a block copolymer composed of a first block chain and a second block chain having different surface free energies, and microphase separation by heating the block copolymer thin film And a sixth step of forming a plurality of columnar phase structures composed of the first block chains on the block copolymer thin film, and a block copolymer thin film having the plurality of columnar phase structures formed on the hydrofluoric acid and A plasma oxide layer in a columnar phase structure is selectively etched by a treatment liquid that is immersed in a treatment liquid containing at least one of an aqueous ammonium fluoride solution and permeates the columnar phase structure, thereby forming a plurality of openings. Seven steps, an eighth step of removing the block copolymer thin film after forming a plurality of openings in the plasma oxide layer, and a plasma oxidation forming a plurality of openings after removing the block copolymer thin film The transfer layer is formed by selectively dry-etching the transfer layer using the layer as a mask to form a plurality of through holes reaching the substrate at locations corresponding to the openings of the transfer layer; And a tenth step of selectively dry-etching the substrate as a mask and forming a plurality of recesses at locations corresponding to the through holes of the substrate.

  In the pattern forming method, the transfer layer may be made of polystyrene.

  A pattern forming method according to the present invention includes a first step of forming a plasma oxide layer having a predetermined thickness on a surface of a substrate by exposing the main surface of a substrate made of silicon to oxygen plasma to oxidize, and a plasma oxide layer A second step of forming a block copolymer thin film comprising a block copolymer composed of a first block chain and a second block chain having different surface free energies, and heating the block copolymer thin film A third step of inducing a microphase separation to form a plurality of columnar phase structures composed of first block chains in the block copolymer thin film, and a block copolymer thin film having a plurality of columnar phase structures formed therein. The formed substrate is immersed in a treatment liquid aqueous solution containing at least one of hydrofluoric acid and an aqueous ammonium fluoride solution, and the columnar phase structure is formed by the treatment liquid that has permeated the columnar phase structure. A fourth step of selectively etching a portion of the plasma oxide layer to form a plurality of openings; a fifth step of removing the block copolymer thin film after forming the plurality of openings in the plasma oxide layer; After removing the block copolymer thin film, the substrate is selectively dry-etched using the plasma oxide layer having a plurality of openings as a mask to form a plurality of recesses at locations corresponding to the openings in the substrate. A process.

  The pattern forming method according to the present invention includes a first step of forming a groove having a side surface of the (111) surface on a substrate made of single crystal silicon and having a main surface of the (110) surface, The second step of forming a plasma oxide layer having a predetermined thickness on the surface of the substrate where the groove is formed by oxidizing the surface including the inside of the groove with oxygen plasma is different from the plasma oxidation layer. A third step of forming a block copolymer thin film composed of a block copolymer composed of a first block chain and a second block chain having surface free energy, and microphase separation by heating the block copolymer thin film A fourth step in which a plurality of columnar phase structures composed of first block chains are induced to form a block copolymer thin film; and a substrate on which the block copolymer thin film having a plurality of columnar phase structures is formed is formed on the substrate. A plurality of openings are formed by selectively etching the plasma oxide layer of the columnar phase structure with a treatment liquid immersed in a treatment liquid aqueous solution containing at least one of hydrofluoric acid and ammonium fluoride aqueous solution and penetrating the columnar phase structure. A fifth step of forming a plurality of openings in the plasma oxide layer, a sixth step of removing the block copolymer thin film, and a plurality of openings after removing the block copolymer thin film. Using the formed plasma oxide layer as a mask, the substrate is selectively wet-etched with an alkaline solution, and a plurality of continuous groove portions are formed in the substrate under a plurality of openings extending and arranged in the direction in which the grooves extend. A seventh step.

  In any of the above pattern forming methods, the first block chain may be composed of polyethylene oxide. The second block chain may be composed of poly (11- [4- (4-butylphenylazo) phenoxy] -undecyl methacrylate).

  As described above, according to the present invention, by using the vertical cylinder phase structure formed by microphase separation, it is possible to obtain an excellent effect that a pattern can be formed without much limitation. Become.

FIG. 1A is a configuration diagram showing a state in each step for explaining a pattern forming method according to Embodiment 1 of the present invention. FIG. 1B is a configuration diagram showing a state in each step for explaining the pattern forming method in Embodiment 1 of the present invention. FIG. 1C is a configuration diagram showing a state in each step for explaining the pattern forming method according to Embodiment 1 of the present invention. FIG. 1D is a configuration diagram showing a state in each step for explaining the pattern forming method in the first embodiment of the present invention. FIG. 1E is a configuration diagram showing a state in each step for explaining the pattern forming method according to the first embodiment of the present invention. FIG. 1F is a configuration diagram showing a state in each step for explaining the pattern forming method according to the first embodiment of the present invention. FIG. 1G is a configuration diagram showing a state in each step for explaining the pattern forming method according to the first embodiment of the present invention. FIG. 2A is a configuration diagram showing a state in each step for explaining a pattern forming method in Embodiment 2 of the present invention. FIG. 2B is a configuration diagram showing a state in each step for explaining a pattern forming method in Embodiment 2 of the present invention. FIG. 2C is a configuration diagram showing a state in each step for explaining the pattern forming method in Embodiment 2 of the present invention. FIG. 2D is a configuration diagram showing a state in each step for explaining a pattern forming method according to the second embodiment of the present invention. FIG. 2E is a configuration diagram showing a state in each step for explaining the pattern forming method according to the second embodiment of the present invention. FIG. 2F is a configuration diagram showing a state in each step for explaining a pattern forming method according to the second embodiment of the present invention. FIG. 2G is a configuration diagram showing a state in each step for explaining the pattern forming method according to the second embodiment of the present invention. FIG. 2H is a configuration diagram showing a state in each step for explaining a pattern forming method according to the second embodiment of the present invention. FIG. 2I is a configuration diagram showing a state in each step for explaining the pattern forming method in the second embodiment of the present invention. FIG. 3A is a configuration diagram showing a state in each step for explaining a pattern forming method according to Embodiment 3 of the present invention. FIG. 3B is a configuration diagram showing a state in each step for explaining a pattern forming method according to Embodiment 3 of the present invention. FIG. 3C is a configuration diagram showing a state in each step for explaining a pattern forming method according to Embodiment 3 of the present invention. FIG. 3D is a configuration diagram showing a state in each step for explaining a pattern forming method according to Embodiment 3 of the present invention. FIG. 3E is a block diagram showing a state in each step for explaining a pattern forming method in Embodiment 3 of the present invention. FIG. 3F is a configuration diagram showing a state in each step for explaining a pattern forming method according to the third embodiment of the present invention. FIG. 3G is a configuration diagram showing a state in each step for explaining a pattern forming method according to Embodiment 3 of the present invention. FIG. 3H is a block diagram showing a state in each step for explaining the pattern forming method in the third embodiment of the present invention. FIG. 3I is a configuration diagram showing a state in each step for explaining a pattern forming method according to the third embodiment of the present invention. FIG. 3J is a configuration diagram showing a state in each step for explaining a pattern forming method according to the third embodiment of the present invention. FIG. 4A is a configuration diagram showing a state in each step for explaining a pattern forming method using a microphase separation structure of a block copolymer. FIG. 4B is a configuration diagram showing a state in each step for explaining a pattern forming method using a microphase separation structure of a block copolymer. FIG. 4C is a configuration diagram showing a state in each step for explaining a pattern forming method using a microphase separation structure of a block copolymer. FIG. 4D is a configuration diagram showing a state in each step for explaining a pattern forming method using a microphase separation structure of a block copolymer. FIG. 4E is a configuration diagram showing a state in each step for explaining a pattern forming method using a microphase separation structure of a block copolymer. FIG. 4F is a configuration diagram showing a state in each step for explaining a pattern forming method using a microphase separation structure of a block copolymer. FIG. 4G is a configuration diagram showing a state in each step for explaining a pattern forming method using a microphase separation structure of a block copolymer. FIG. 4H is a configuration diagram showing a state in each step for explaining a pattern forming method using a microphase separation structure of a block copolymer.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1]
First, Embodiment 1 of the present invention will be described with reference to FIGS. 1A to 1G. 1A to 1G are configuration diagrams showing states in respective steps for explaining a pattern forming method according to Embodiment 1 of the present invention. 1A to 1G schematically show cross sections.

  First, as shown in FIG. 1A, a substrate 101 made of silicon is prepared. For example, a commercially available silicon wafer having a diameter of 4 inches may be used as the substrate 101. Next, as shown in FIG. 1B, the main surface of the substrate 101 is oxidized by exposing it to oxygen plasma, and a plasma oxide layer 102 is formed on the surface of the substrate 101.

  For example, the prepared substrate 101 is immersed in a mixed solution of 98% sulfuric acid / 30% hydrogen peroxide (volume ratio 3/1) for 10 minutes, and then washed with water for 10 minutes. In addition, a treatment of immersing in a 1% hydrofluoric acid aqueous solution for 1 minute is performed to remove the natural oxide film on the surface and expose the hydrophobic silicon surface. Next, washing with water is performed for 10 minutes, and then the substrate 101 is spin-dried at a rotational speed of 2000 rpm for 5 minutes.

After the pretreatment described above, exposure to the oxygen plasma described above is performed using an electron cyclotron resonance (ECR) etching apparatus. For example, the plasma generation conditions were such that O ₂ gas was used as the reaction gas, the flow rate was about 10 sccm, and the microwave power was about 200 W. Note that sccm is a unit of flow rate, and indicates that a fluid at 0 ° C. and 1013 hPa flows 1 cm ³ per minute. Under this condition, the surface of the substrate 101 may be irradiated with oxygen plasma for about 1 second. Assuming that the refractive index of the plasma oxide layer 102 formed in this way is 1.46, the film thickness is measured by ellipsometry. As a result, an extremely thin plasma oxide layer 102 having a thickness of 2 nm or less is formed. It is confirmed that

  Next, as shown in FIG. 1C, on the plasma oxide layer 102, a block copolymer thin film 103 made of a block copolymer composed of a first block chain and a second block chain having different surface free energies. Form.

  When forming the block copolymer thin film 103, the surface free energy of the substrate surface is controlled as necessary. First, the substrate 101 on which the plasma oxide layer 102 is formed is subjected to heat treatment on a hot plate at 100 ° C. for 45 seconds to remove physical water on the surface of the plasma oxide layer 102, and immediately thereafter at room temperature (about 20 ° C.). To expose to hexamethyldisilazane (HMDS) vapor. This exposure time is set so that the contact angle of water on the surface of the plasma oxide layer 102 after exposure is about 5-110 degrees. When the contact angle of water was measured with a droplet volume of 1 microliter on the surface of the plasma oxide layer 102 exposed to HMDS vapor for 45 seconds, it was confirmed to be about 53 degrees.

  After the processing described above, the block copolymer thin film 103 is formed. The block copolymer thin film 103 is formed as follows. First, a mixed toluene solution of an amphiphilic side chain liquid crystal block copolymer and polyethylene glycol monomethyl ether (PEGME) is prepared. The amphiphilic side chain liquid crystal block copolymer is composed of, for example, polyethylene oxide (PEO) and poly (11- [4- (4-butylphenylazo) phenoxy] -undecyl methacrylate) (PMA (Az)). It is a block copolymer (PEO114-b-PMA (Az) 51).

  In this toluene mixed solution, the weight percentage of the block copolymer to toluene was 1.0%, and the weight percentage of the PEGME to the PEO block chain was 55%. Polyethylene oxide is the first block chain, and poly (11- [4- (4-butylphenylazo) phenoxy] -undecyl methacrylate) is the second block chain.

  The toluene mixed solution thus prepared is spin-coated on the above-described plasma oxide layer 102 having been subjected to HMDS treatment at a rotational speed of 2000 rpm for 30 seconds to form a block copolymer thin film 103. .

  Next, the block copolymer thin film 103 is heated to induce microphase separation, and as shown in FIG. 1D, a plurality of columnar phase structures (vertical cylinder phase structures) 104 composed of the first block chains are blocked. The polymer thin film 103 is formed. In this case, the PEGME molecules 141 are segregated in the columnar phase structure 104. For example, heat treatment may be performed on the substrate 101 under conditions of a heating temperature of 110 ° C. and a heating time of 2 hours under the atmosphere. The heat treatment may be performed using an oven. When the surface of the block copolymer thin film 103 after the heat treatment is observed with an atomic force microscope (AFM), a dot structure arranged in a hexagonal lattice pattern is observed in the AFM phase image, and a columnar shape perpendicular to the plane of the substrate 101 is observed. It is confirmed that the phase structure 104 is formed. The distance between adjacent columnar phase structures 104 is about 32 nm.

  Next, as shown in FIG. 1E, the block copolymer thin film 103 in which the plurality of columnar phase structures 104 are formed is immersed in a treatment liquid 105 made of an aqueous ammonium fluoride solution. The substrate 101 on which the block copolymer thin film 103 is formed may be immersed for about 2 minutes in the processing liquid 105 accommodated in a predetermined container (not shown). The treatment liquid 105 may have an ammonium fluoride concentration of 33 wt%. By this treatment, the plasma oxide layer 102 in the columnar phase structure 104 is selectively etched by ammonium fluoride (treatment liquid 105) that has permeated the columnar phase structure 104, and a plurality of openings 106 are formed as shown in FIG. 1F. Form. At this time, a part of the reaction product 142 generated along with the dissolution of the plasma oxide layer 102 described above diffuses from the columnar phase structure 104 to the treatment liquid 105.

  As described above, when the plurality of openings 106 are formed in the plasma oxide layer 102, the substrate is washed with water and spin-dried at a rotational speed of 2000 rpm for 5 minutes to dry the substrate 101 on which the block copolymer thin film 103 is formed. To do. Next, the block copolymer thin film 103 is removed. For example, the block copolymer thin film 103 may be removed by immersing it in a solvent in which tetrahydrofuran and water are mixed at a volume ratio of 6: 4 for 15 minutes while applying ultrasonic waves.

  After the block copolymer thin film 103 is removed as described above, the state of the plasma oxide layer 102 formed on the surface of the substrate 101 is observed by AFM, and a plurality of hexagonal lattices arranged in the AFM height image are observed. Opening 106 was observed. The distance between adjacent openings 106 is about 32 nm. It was confirmed that the nanohole array composed of a plurality of openings 106 was transferred to the plasma oxide layer 102, which was the same as the interval between the columnar phase structures 104 observed on the surface of the block copolymer thin film 103 before removal. .

Next, the substrate 101 is selectively dry-etched using the plasma oxide layer 102 in which the plurality of openings 106 are formed as a mask, and a plurality of recesses 107 are formed at locations corresponding to the openings 106 in the substrate 101 as shown in FIG. 1G. Form. For example, the substrate 101 may be etched by dry etching with a chlorine-based gas using an ECR etching apparatus. For example, Cl ₂ , O ₂ , and SF ₆ may be used as the etching gas, the flow rates may be 15 sccm, 1.5 sccm, and 1.5 sccm, respectively, and the microwave power may be about 400 W. The etching time may be about 60 seconds.

  After the recess 107 is formed as described above, the plasma oxide layer 102 is removed using a 1% hydrofluoric acid solution. When the surface state of the substrate 101 after removing the plasma oxide layer 102 is observed with a scanning electron microscope (SEM), it is observed that a plurality of recesses 107 having an interval of about 32 nm and a depth of about 60 nm are formed. It was done.

[Embodiment 2]
Next, Embodiment 2 of the present invention will be described with reference to FIGS. 2A to 2I. 2A to 2I are configuration diagrams showing states in respective steps for explaining the pattern forming method according to the second embodiment of the present invention. 2A to 2I schematically show cross sections.

  First, as shown in FIG. 2A, a substrate 201 made of silicon is prepared. For example, a commercially available silicon wafer having a diameter of 4 inches may be used as the substrate 201. Further, the prepared substrate 201 is immersed in a mixed solution of 98% sulfuric acid / 30% hydrogen peroxide solution (volume ratio 3/1) for 10 minutes, and then washed with water for 10 minutes. In addition, a treatment of immersing in a 1% hydrofluoric acid aqueous solution for 1 minute is performed to remove the natural oxide film on the surface and expose the hydrophobic silicon surface. Next, washing with water is performed for 10 minutes, and then the substrate 201 is spin-dried at a rotational speed of 2000 rpm for 5 minutes.

  Next, as shown in FIG. 2B, a transfer layer 202 made of an organic material is formed on the substrate 201. Subsequently, a coating glass material is applied on the transfer layer 202, and an SOG (Spin on Glass) layer 203 is formed. Form.

  For example, polystyrene may be used as the organic material. First, a 2 wt% orthodichlorobenzene solution of polystyrene having a weight average molecular weight of about 200,000 and a polydispersity of about 1.8 is prepared. Next, the prepared orthodichlorobenzene solution is spin-coated on the stomach plate 201 at a rotational speed of 2000 rotations / minute for 60 seconds to form a transfer layer 202 made of polystyrene. The thickness of the transfer layer 202 formed in this way was measured by ellipsometry, and was about 100 nm.

  Further, as the coating glass material, hydrogenated silsesquioxane (HSQ) used as a well-known interlayer insulating film may be used. First, an HSQ MIBK solution in which a methyl isobutyl ketone (MIBK) solution of HSQ (trade name: Fox-16, manufactured by Dow Corning) was diluted 40 times with MIBK was prepared. The solution thus adjusted is spin-coated on the transfer layer 202 of the substrate 201 at a rotation speed of 7000 rpm and a time of 30 seconds. Next, the coating film formed by coating is subjected to hot plate heat treatment in the air under the heating conditions of a heating temperature of 240 ° C. and a heating time of 10 minutes, so that the SOG layer 203 is formed.

  The coating film by HSQ has a flattening effect as a feature of the material used for the interlayer insulating film. By performing the treatment at the above-described heat treatment temperature, pinholes existing in the film immediately after coating are filled, and at the same time, planarization proceeds and a continuous extremely thin SOG layer 203 can be formed. When the film thickness of the SOG layer 203 formed as described above was measured by ellipsometry, it was about 10 nm. Since polystyrene is insoluble in MIBK, which is an HSQ solvent, the transfer layer 202 is not dissolved when HSQ is spin-coated.

  Next, the SOG layer 203 is thinned to a predetermined thickness. The SOG layer 203 is thinned using a solution that dissolves it. First, a TMAH solution in which a 2.38% tetramethylammonium hydroxide (TMAH) aqueous solution (trade name: MICROPOSIT MF-CD26, manufactured by Shipley Co., Ltd.), which is a standard developer of photoresist, is diluted 10 times with pure water is prepared. To do. Next, the substrate 201 on which the SOG layer 203 is formed is immersed in the prepared TMAH solution. By adjusting the immersion time, the SOG layer 203 was thinned to a film thickness of about 2 nm.

Next, oxygen plasma is applied to the thinned SOG layer 203 to oxidize the SOG layer 203 to form a plasma oxide layer 204 as shown in FIG. 2C. The plasma oxide layer 204 is formed on the transfer layer 202. For example, the above-described oxygen plasma exposure is performed using an ECR etching apparatus. For example, the plasma generation conditions were such that O ₂ gas was used as the reaction gas, the flow rate was about 10 sccm, and the microwave power was about 200 W. Under this condition, the SOG layer 203 may be irradiated with oxygen plasma for about 1 second. sccm is a unit of flow rate, and indicates that a fluid of 0 ° C. and 1013 hPa flows 1 cm ³ per minute.

  Next, as shown in FIG. 2D, on the plasma oxide layer 204, a block copolymer thin film 205 made of a block copolymer composed of a first block chain and a second block chain having different surface free energies. Form.

  When the block copolymer thin film 205 is formed, first, the substrate 201 on which the plasma oxide layer 204 is formed is heated on a hot plate at 100 ° C. for 45 seconds, and physical water on the surface of the plasma oxide layer 204 is removed. Immediately after removal, it is exposed to hexamethyldisilazane (HMDS) vapor at room temperature (about 20 ° C.). This exposure time is set so that the contact angle of water on the surface of the plasma oxide layer 204 after exposure is about 5-110 degrees as necessary. When the contact angle of water was measured with a droplet volume of 1 microliter on the surface of the plasma oxide layer 204 exposed to HMDS vapor for 45 seconds, it was confirmed to be about 53 degrees.

  After the processing described above, the block copolymer thin film 205 is formed. The block copolymer thin film 205 is formed as follows. First, a mixed toluene solution of an amphiphilic side chain liquid crystal block copolymer and polyethylene glycol monomethyl ether (PEGME) is prepared. The amphiphilic side chain liquid crystal block copolymer is composed of, for example, polyethylene oxide (PEO) and poly (11- [4- (4-butylphenylazo) phenoxy] -undecyl methacrylate) (PMA (Az)). It is a block copolymer (PEO114-b-PMA (Az) 51).

  In this toluene mixed solution, the weight percentage of the block copolymer to toluene was 1.0%, and the weight percentage of the PEGME to the PEO block chain was 55%. Polyethylene oxide is the first block chain, and poly (11- [4- (4-butylphenylazo) phenoxy] -undecyl methacrylate) is the second block chain. Here, in the block copolymer, it is important that the first block chain is polyethylene oxide, and the second block chain is poly (11- [4- (4-butylphenylazo) phenoxy] -undecyl. Methacrylate).

  The toluene mixed solution thus prepared is spin-coated on the above-described plasma oxide layer 204 that has been subjected to the HMDS treatment at a rotational speed of 2000 rpm for 30 seconds to form a block copolymer thin film 205. .

  Next, the block copolymer thin film 205 is heated to induce microphase separation, and as shown in FIG. 2E, a plurality of columnar phase structures (vertical cylinder phase structures) 206 composed of the first block chains are blocked. The polymer thin film 205 is formed. In this case, the PEGME molecules 261 are segregated in the columnar phase structure 206. For example, heat treatment may be performed on the substrate 201 under conditions of a heating temperature of 110 ° C. and a heating time of 2 hours under the atmosphere. The heat treatment may be performed using an oven. When the surface of the block copolymer thin film 205 after the heat treatment is observed with an atomic force microscope (AFM), a dot structure arranged in a hexagonal lattice pattern is observed in the AFM phase image, and a columnar shape perpendicular to the plane of the substrate 201 is observed. It is confirmed that the phase structure 206 is formed. The distance between adjacent columnar phase structures 206 is about 32 nm.

  Next, as shown in FIG. 2F, the block copolymer thin film 205 in which the plurality of columnar phase structures 206 are formed is immersed in a treatment liquid 207 made of an aqueous ammonium fluoride solution. The substrate 201 on which the block copolymer thin film 205 is formed may be immersed in a processing solution 207 contained in a predetermined container (not shown) for about 2 minutes. The treatment liquid 207 may have an ammonium fluoride concentration of 33 wt%. By this treatment, the plasma oxide layer 204 in the columnar phase structure 206 is selectively etched by ammonium fluoride (treatment liquid 207) that has permeated the columnar phase structure 206, and a plurality of openings 208 are formed as shown in FIG. 2G. Form. At this time, a part of the reaction product 262 generated along with the dissolution of the plasma oxide layer 204 described above diffuses from the columnar phase structure 206 to the treatment liquid 207.

  As described above, when the plurality of openings 208 are formed in the plasma oxide layer 204, the substrate is washed with water and spin-dried at a rotational speed of 2000 rpm for 5 minutes to dry the substrate 201 on which the block copolymer thin film 205 is formed. To do. Next, the block copolymer thin film 205 is removed. For example, the block copolymer thin film 205 may be removed by immersing in a solvent in which tetrahydrofuran and water are mixed at a volume ratio of 6: 4 for 15 minutes while applying ultrasonic waves.

  After removing the block copolymer thin film 205 as described above, the state of the plasma oxide layer 204 formed on the substrate 201 via the transfer layer 202 as shown in FIG. A plurality of openings 208 arranged in a hexagonal lattice pattern were observed in the height image. The distance between adjacent openings 208 is about 32 nm. It was confirmed that the nanohole array was transferred to the plasma oxide layer 204, which was the same as the interval between the columnar phase structures 206 observed on the surface of the block copolymer thin film 205 before removal.

As described above, after the block copolymer thin film 205 is removed, the transfer layer 202 is selectively dry-etched using the plasma oxide layer 204 in which the plurality of openings 208 are formed as a mask to form openings 208 in the transfer layer 202. A plurality of through holes 209 reaching the substrate 201 are formed at corresponding locations. For example, by using an ECR etching apparatus and exposing to oxygen plasma, the transfer layer 202 may be selectively removed by etching using the plasma oxide layer 204 in which the opening 208 is formed as a mask. The etching conditions may be, for example, that O ₂ gas is supplied at a flow rate of about 10 sccm and the microwave power is about 200 W. The etching time may be about 120 seconds.

  When the surface state of the substrate 201 after forming the through holes 209 was observed with a scanning electron microscope (SEM), it was observed that a plurality of through holes 209 having an interval of about 32 nm and a depth of about 100 nm were formed. It was done.

  Next, the substrate 201 is selectively dry-etched using the transfer layer 202 in which the plurality of through holes 209 are formed as a mask, and a plurality of recesses 210 are formed at locations corresponding to the through holes 209 of the substrate 201 as shown in FIG. Form. FIG. 2I shows a state where the transfer layer 202 and the plasma oxide layer 204 are removed.

For example, the substrate 201 may be etched by dry etching with a chlorine-based gas using an ECR etching apparatus. For example, Cl ₂ and SF ₆ are used as the etching gas, the flow rates are 15 sccm and 2 sccm, respectively, and the microwave power is about 400 W. The etching time may be about 45 seconds.

  After forming the recesses 210 as described above, the transfer layer 202 is removed using a mixed solution of 98% sulfuric acid and 30% hydrogen peroxide (volume ratio 3/1), and at the same time, the plasma oxidation layer 204 is removed. Remove. For example, the substrate 201 may be immersed in the mixed solution for about 10 minutes. Thereafter, washing with water for 1 minute is performed. When the surface state of the substrate 201 after removing the transfer layer 202 and the plasma oxide layer 204 as described above is observed with a scanning electron microscope (SEM), a plurality of recesses having an interval of about 32 nm and a depth of about 100 nm are obtained. A state in which 210 was formed was observed.

  According to the second embodiment described above, the substrate 201 does not need to be made of silicon, and the substrate 201 is made of any material. Pattern formation is possible.

[Embodiment 3]
Next, Embodiment 3 of the present invention will be described with reference to FIGS. 3A to 3J. 3A to 3J are configuration diagrams showing states in respective steps for explaining the pattern forming method according to the third embodiment of the present invention. 3A to 3G and FIG. 3I schematically show cross sections. Moreover, FIG. 3H and FIG. 3J have shown the plane.

  First, as shown in FIG. 3A, a substrate 301 made of silicon is prepared. For example, a commercially available silicon wafer having a diameter of 4 inches may be used as the substrate 301. The substrate 301 has a main surface plane orientation of (110). Next, as shown in FIG. 3B, a groove 301a is formed on the surface of the substrate 301 by, for example, dry etching using a mask pattern formed by a well-known lithography technique as a mask. The side wall of the groove 301a is a (111) plane. Note that a plurality of grooves 301 a arranged in parallel to each other are formed in the substrate 301. In FIG. 3B, a part of the substrate 301 is shown.

  For example, the prepared substrate 301 is immersed in a mixed solution of 98% sulfuric acid / 30% hydrogen peroxide solution (volume ratio 3/1) for 10 minutes, and then washed with water for 10 minutes. In addition, a treatment of immersing in a 1% hydrofluoric acid aqueous solution for 1 minute is performed to remove the natural oxide film on the surface and expose the hydrophobic silicon surface. Next, the substrate is washed with water for 10 minutes, and then the substrate 301 is spin-dried at a rotational speed of 2000 rpm for 5 minutes.

  Next, heat treatment is performed in a generally used annealing furnace in an oxygen atmosphere at a heat treatment temperature of 1000 ° C. and a heat treatment time of 30 minutes to form a thermal silicon oxide film having a thickness of about 30 nm on the main surface of the substrate 301. To do. Next, a photoresist (trade name: OFPR-800, manufactured by Tokyo Ohka Kogyo Co., Ltd.) is spin-coated on the formed thermal silicon oxide film at 4000 rpm for 20 seconds to form a resist film having a thickness of about 1 μm. In addition, heat treatment is performed on a hot plate at 120 ° C. for 2 minutes.

Next, using a photomask in which a pattern layer is formed of a chromium film with a commonly used contact exposure apparatus, ultraviolet rays (wavelength of about 365 to 435 nm) are irradiated at an exposure amount of about 50 mJ / cm ^2. Perform exposure. By this exposure, a latent image of a line & space pattern having a line width of about 1 μm and a pitch of about 2 μm is formed. Next, the resist film on which a latent image was formed by exposure was developed to form a resist mask having a line & space pattern having a line width of about 1 μm and a pitch of 2 μm. Here, the extending direction of the line & space pattern is a direction in which the side surface of the groove 301a of the substrate 301 formed by the resist mask becomes the (111) plane.

Next, using a reactive ion etching (RIE) etching apparatus, the thermal silicon oxide film formed on the surface of the substrate 301 is selectively etched using the resist mask as a mask. For example, CF ₄ diluted with argon gas is used as an etching gas, argon gas is 120 sccm, CF ₄ gas is 40 sccm, supplied to the processing chamber, the degree of vacuum is 6 Pa, and the self-bias voltage of radio frequency (RF) is about 400V. And it is sufficient. The etching time may be about 120 seconds. sccm is a unit of flow rate, and indicates that a fluid of 0 ° C. and 1013 hPa flows 1 cm ³ per minute.

  By this etching process, the resist mask pattern is transferred to the thermal silicon oxide film, and an inorganic mask is formed. Next, the substrate 301 is anisotropically etched by wet etching using a 50% aqueous potassium hydroxide (KOH) solution to form a plurality of grooves 301a. As is well known, since the (111) plane of silicon is harder to etch than the (100) plane in anisotropic etching with alkali, the substrate 301 made of silicon with the main surface of (110) is described above. By performing the etching process as described above, the groove 301a whose side wall becomes the (111) plane is formed.

  Thereafter, the substrate is immersed in a mixed solution of 98% sulfuric acid / 30% hydrogen peroxide solution (volume ratio 3/1) for 10 minutes, and then washed with water for 10 minutes. Next, a treatment of immersing in a 1% hydrofluoric acid aqueous solution for 1 minute is performed to remove the above-described resist mask and thermal silicon oxide film. Thereafter, the substrate was washed with water for 10 minutes, spin-dried at a rotational speed of 2000 rotations / minute, and for 5 minutes to dry the substrate 301.

After forming the groove 301a as described above, as shown in FIG. 3C, the main surface of the substrate 301 is oxidized by exposing it to oxygen plasma, and a plasma oxide layer 302 is formed on the surface of the substrate 301. For example, exposure to the above-described oxygen plasma is performed using an electron cyclotron resonance (ECR) etching apparatus. For example, the plasma generation conditions were such that O ₂ gas was used as the reaction gas, the flow rate was about 10 sccm, and the microwave power was about 200 W. Note that sccm is a unit of flow rate, and indicates that a fluid at 0 ° C. and 1013 hPa flows 1 cm ³ per minute. Under this condition, the surface of the substrate 301 may be irradiated with oxygen plasma for about 1 second. Assuming the refractive index of the plasma oxide layer 302 thus formed is 1.46, the film thickness is measured by ellipsometry. As a result, an extremely thin plasma oxide layer 302 having a thickness of 2 nm or less is formed. It is confirmed that

  Next, as shown in FIG. 3D, on the plasma oxide layer 302, a block copolymer thin film 303 made of a block copolymer composed of a first block chain and a second block chain having different surface free energies. Form.

  When the block copolymer thin film 303 is formed, first, the substrate 301 on which the plasma oxide layer 302 is formed is heated on a hot plate at 100 ° C. for 45 seconds, and physical water on the surface of the plasma oxide layer 302 is removed. Immediately after removal, it is exposed to hexamethyldisilazane (HMDS) vapor at room temperature (about 20 ° C.). This exposure time is set so that the contact angle of water on the surface of the plasma oxide layer 302 after the exposure is about 5-110 degrees as necessary. When the contact angle of water was measured with a droplet volume of 1 microliter on the surface of the plasma oxide layer 302 exposed to HMDS vapor for 45 seconds, it was confirmed to be about 53 degrees.

  After the processing described above, the block copolymer thin film 303 is formed. The block copolymer thin film 303 is formed as follows. First, a mixed toluene solution of an amphiphilic side chain liquid crystal block copolymer and polyethylene glycol monomethyl ether (PEGME) is prepared. The amphiphilic side chain liquid crystal block copolymer is composed of, for example, polyethylene oxide (PEO) and poly (11- [4- (4-butylphenylazo) phenoxy] -undecyl methacrylate) (PMA (Az)). It is a block copolymer (PEO114-b-PMA (Az) 51).

  In this toluene mixed solution, the weight percentage of the block copolymer to toluene was 1.0%, and the weight percentage of the PEGME to the PEO block chain was 55%. Polyethylene oxide is the first block chain, and poly (11- [4- (4-butylphenylazo) phenoxy] -undecyl methacrylate) is the second block chain.

  The toluene mixed solution thus prepared is spin-coated on the above-described plasma oxidation layer 302 that has been subjected to the HMDS treatment at a rotational speed of 2000 rpm for 30 seconds to form a block copolymer thin film 303. .

  Next, the block copolymer thin film 303 is heated to induce microphase separation, and as shown in FIG. 3E, a plurality of columnar phase structures (vertical cylinder phase structures) 304 composed of the first block chains are blocked. The polymer thin film 303 is formed. In this case, the PEGME molecules 341 are segregated in the columnar phase structure 304. For example, heat treatment may be performed on the substrate 301 under conditions of a heating temperature of 110 ° C. and a heating time of 2 hours under the atmosphere. The heat treatment may be performed using an oven.

  When the surface of the block copolymer thin film 303 after the heat treatment is observed with an atomic force microscope (AFM), a dot structure arranged in a hexagonal lattice pattern is observed in the AFM phase image, and a columnar shape perpendicular to the plane of the substrate 301 is observed. It is confirmed that the phase structure 304 is formed. The columnar phase structures 304 are formed side by side in the direction in which the grooves 301a extend, and the distance between adjacent columnar phase structures 304 is about 32 nm.

  Next, as shown in FIG. 3F, the block copolymer thin film 303 in which a plurality of columnar phase structures 304 are formed is immersed in a treatment liquid 305 made of an aqueous ammonium fluoride solution. The substrate 301 on which the block copolymer thin film 303 is formed may be immersed in a processing liquid 305 accommodated in a predetermined container (not shown) for about 2 minutes. The treatment liquid 305 may have an ammonium fluoride concentration of 33 wt%. By this treatment, the plasma oxide layer 302 in the columnar phase structure 304 is selectively etched with ammonium fluoride (treatment liquid 305) that has permeated the columnar phase structure 304, and a plurality of openings 306 are formed as shown in FIG. 3G. Form. At this time, a part of the reaction product 342 generated along with the dissolution of the plasma oxide layer 302 described above diffuses from the columnar phase structure 304 to the treatment liquid 305.

  As described above, when the plurality of openings 306 are formed in the plasma oxide layer 302, the plasma oxide layer 302 is washed with water and subjected to spin drying at a rotational speed of 2000 rpm for 5 minutes to dry the substrate 301 on which the block copolymer thin film 303 is formed. To do. Next, the block copolymer thin film 303 is removed. For example, the block copolymer thin film 303 may be removed by immersing in a solvent in which tetrahydrofuran and water are mixed at a volume ratio of 6: 4 for 15 minutes while applying ultrasonic waves.

  After removing the block copolymer thin film 303 as described above, the state of the plasma oxide layer 302 formed on the surface of the substrate 301 was observed by AFM. As shown in FIGS. 3H and 3I, the height of the AFM was increased. A plurality of openings 306 arranged in a hexagonal lattice pattern were observed in the image. The plurality of openings 306 are arranged side by side in the direction in which the groove 301a extends. The distance between adjacent openings 306 is about 32 nm. It was confirmed that the nanohole array composed of a plurality of openings 306 was transferred to the plasma oxide layer 302 with the same spacing as the columnar phase structure 304 observed on the surface of the block copolymer thin film 303 before removal. .

  As described above, after the block copolymer thin film 303 is removed, the substrate 301 is selectively wet-etched with an alkaline solution using the plasma oxide layer 302 having a plurality of openings 306 as a mask. By this etching, as shown in FIGS. 3I and 3J, a plurality of continuous groove portions 307 are formed in the substrate 301 under a plurality of openings 306 extending and arranged in the direction in which the grooves 301a extend. For example, a 50% potassium hydroxide (KOH) aqueous solution may be used as the alkaline solution.

  In this anisotropic etching of single crystal silicon with an alkaline solution, the (100) plane is etched faster. In addition, since the etching is wet etching, the direction in which the etching acts is isotropic, and the etching proceeds under the plasma oxide layer 302 in which the opening 306 is not formed. As a result, etching proceeds in the extending direction of the groove 301a starting from the opening 306, and a plurality of groove parts 307 extending and arranged in the extending direction of the groove 301a are formed. Note that the groove 307 is formed to a depth of about 100 nm. As described above, even when the plasma oxide layer 302 having a plurality of openings 306 arranged in a hexagonal lattice is used as an etching mask, the plane orientation of the main surface of the substrate 301 made of single crystal silicon or the groove 301a. By controlling the extending direction, the groove 307 can be formed.

  After the groove 307 is formed as described above, the plasma oxide layer 302 is removed using a 1% hydrofluoric acid solution. When the surface state of the substrate 301 after the plasma oxide layer 302 is removed is observed with a scanning electron microscope (SEM), a plurality of grooves 307 having an interval of about 27 nm and a depth of about 100 nm are formed. Observed.

  According to the present invention described above, first, a plasma oxide layer oxidized by plasma is used. Therefore, as a thin oxide layer necessary for patterning using a vertical cylinder phase structure formed by microphase separation, Dry etching can be applied. As a result, a high density pattern having a higher aspect ratio than the maximum aspect ratio (1.41) of the pattern that can be transferred by the wet etching method can be transferred to the substrate. Further, by using the transfer layer, it is possible to form a pattern not only on the silicon substrate but also on various substrates.

  In addition, by appropriately selecting the plane direction of the silicon substrate and the direction of the groove and applying anisotropic etching with alkali in the patterning of the silicon substrate, it becomes possible to form a stripe-shaped groove portion in the silicon substrate.

  The present invention is not limited to the embodiment described above, and many modifications and combinations can be implemented by those having ordinary knowledge in the art within the technical idea of the present invention. It is obvious. For example, in the above description, the ammonium fluoride aqueous solution is used as the treatment liquid. However, the present invention is not limited to this, and the treatment liquid may include at least one of hydrofluoric acid and ammonium fluoride aqueous solution. Good. A mixed liquid of hydrofluoric acid and an aqueous ammonium fluoride solution may be used as the treatment liquid. Further, the transfer layer is not limited to polystyrene, but may be made of so-called spin-on carbon that can be spin-coated.

  DESCRIPTION OF SYMBOLS 101 ... Substrate, 102 ... Plasma oxide layer, 103 ... Block copolymer thin film, 104 ... Columnar phase structure, 105 ... Treatment liquid, 106 ... Opening, 107 ... Recess, 141 ... PEGME molecule, 142 ... Reaction product.

  DESCRIPTION OF SYMBOLS 201 ... Substrate, 202 ... Transfer layer, 203 ... SOG (Spin on Glass) layer, 204 ... Plasma oxidation layer, 205 ... Block copolymer thin film, 206 ... Columnar phase structure, 207 ... Treatment liquid, 208 ... Opening, 209 ... through hole, 210 ... recess, 261 ... PEGME molecule, 262 ... reaction product.

  301 ... Substrate, 301a ... Groove, 302 ... Plasma oxide layer, 303 ... Block copolymer thin film, 304 ... Columnar phase structure, 305 ... Treatment liquid, 306 ... Opening, 307 ... Groove, 341 ... PEGME molecule, 342 ... Reaction Product.

Claims (6)

A first step of forming a transfer layer made of an organic material on a substrate;
A second step of forming a SOG layer by applying a coating glass material on the transfer layer;
A third step of thinning the SOG layer to a predetermined thickness;
A fourth step in which oxygen plasma is applied to the thinned SOG layer to oxidize the SOG layer to form a plasma oxide layer;
A fifth step of forming a block copolymer thin film made of a block copolymer composed of a first block chain and a second block chain having different surface free energies on the plasma oxide layer;
A sixth step of heating the block copolymer thin film to induce microphase separation to form a plurality of columnar phase structures composed of the first block chains in the block copolymer thin film;
A plurality of the block copolymer thin films formed with the columnar phase structure are immersed in a treatment liquid containing at least one of hydrofluoric acid and an aqueous ammonium fluoride solution, and the columnar phase is formed by the treatment liquid that has permeated the columnar phase structure. A seventh step of selectively etching the plasma oxide layer in the structure portion to form a plurality of openings;
An eighth step of removing the block copolymer thin film after forming the plurality of openings in the plasma oxide layer;
After the block copolymer thin film is removed, the transfer layer is selectively dry-etched using the plasma oxide layer having the plurality of openings as a mask, at a position corresponding to the openings of the transfer layer. A ninth step of forming a plurality of through holes reaching the substrate;
And a tenth step of selectively dry-etching the substrate using the transfer layer having the plurality of through-holes as a mask to form a plurality of recesses at locations corresponding to the through-holes of the substrate. A pattern forming method. In the pattern formation method of Claim 1,
The pattern forming method, wherein the transfer layer is made of polystyrene. A first step of forming a plasma oxide layer having a predetermined thickness on the surface of the substrate by oxidizing the main surface of the substrate composed of silicon by exposing it to oxygen plasma;
A second step of forming a block copolymer thin film composed of a block copolymer composed of a first block chain and a second block chain having different surface free energies on the plasma oxide layer;
A third step of heating the block copolymer thin film to induce microphase separation to form a plurality of columnar phase structures composed of the first block chains in the block copolymer thin film;
The substrate on which the block copolymer thin film formed with a plurality of the columnar phase structures is formed is immersed in a treatment solution containing at least one of hydrofluoric acid and an aqueous ammonium fluoride solution, and penetrates the columnar phase structure. A fourth step of selectively etching the plasma oxide layer in the columnar phase structure portion with a treatment liquid to form a plurality of openings;
A fifth step of removing the block copolymer thin film after forming the plurality of openings in the plasma oxide layer;
After removing the block copolymer thin film, the substrate is selectively dry-etched using the plasma oxide layer having the plurality of openings as a mask, and a plurality of portions are formed at locations corresponding to the openings of the substrate. And a sixth step of forming a recess. A first step of forming a groove having a side surface of a (111) surface in a substrate made of single crystal silicon and having a main surface of (110) surface;
A second step of forming a plasma oxide layer having a predetermined thickness on the surface of the substrate on which the groove is formed by oxidizing the surface including the inside of the groove of the substrate on which the groove is formed by exposure to oxygen plasma. When,
A third step of forming a block copolymer thin film comprising a block copolymer composed of a first block chain and a second block chain having different surface free energies on the plasma oxide layer;
A fourth step of heating the block copolymer thin film to induce microphase separation to form a plurality of columnar phase structures composed of the first block chains in the block copolymer thin film;
The substrate on which the block copolymer thin film formed with a plurality of the columnar phase structures is formed is immersed in a treatment solution containing at least one of hydrofluoric acid and an aqueous ammonium fluoride solution, and penetrates the columnar phase structure. A fifth step of selectively etching the plasma oxide layer in the columnar phase structure portion with a treatment liquid to form a plurality of openings;
A sixth step of removing the block copolymer thin film after forming the plurality of openings in the plasma oxide layer;
After removing the block copolymer thin film, the substrate is selectively wet-etched with an alkaline solution using the plasma oxide layer having a plurality of openings as a mask and extended in the direction in which the groove extends. And a seventh step of forming, on the substrate, a plurality of continuous groove portions below the plurality of opening portions that are present and lined up. In the pattern formation method of any one of Claims 1-4,
The pattern forming method, wherein the first block chain is made of polyethylene oxide. In the pattern formation method of Claim 5,
The pattern forming method, wherein the second block chain is composed of poly (11- [4- (4-butylphenylazo) phenoxy] -undecyl methacrylate).

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