Method for forming resist underlayer film and patterning process

Abstract

To provide a method for forming, by plasma irradiation, a resist underlayer film with excellent dry etching resistance and film thickness uniformity.SOLUTION: A method for forming a resist underlayer film includes the steps of: (i) applying a coating of a composition containing (A) a polymer and (B) an organic solvent, and performing heat treatment; and (ii) forming a resist underlayer film by plasma irradiation, where the polymer (A) contains a constitutional unit of formula (1) and has a weight-average molecular weight of 2,500 to 20,000 (where Ar1 and Ar2 represent a benzene ring or naphthalene ring, X represents a structure represented by a specific formula, Y represents an organic group, and k represents 0 or 1).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for forming a resist underlayer film that can be used for fine patterning by a multilayer resist method in the manufacturing process of a semiconductor device, and a method for forming a pattern using the resist underlayer film. [Background technology]

[0002] As LSIs become more highly integrated and faster, pattern dimensions are becoming finer. Lithography technology has achieved the formation of finer patterns by shortening the wavelength of light sources and selecting appropriate resist compositions to match them, in line with this trend. The core of this technology is a positive photoresist composition used in a single layer. This single-layer positive photoresist composition has a skeleton in the resist resin that is resistant to dry etching using chlorine- or fluorine-based gas plasma, and also has a switching mechanism that dissolves the exposed areas, forming a pattern by dissolving the exposed areas, and then dry etching the substrate using the remaining resist pattern as an etching mask.

[0003] However, when the thickness of the photoresist film used is made finer, that is, when the pattern width is made smaller, the resolution performance of the photoresist film is reduced, and when an attempt is made to develop the photoresist film into a pattern using a developer, the so-called aspect ratio becomes too large, resulting in problems such as pattern collapse. For this reason, photoresist films have been made thinner as patterns become finer.

[0004] On the other hand, in the processing of a substrate to be processed, a method is usually used in which a photoresist film on which a pattern is formed is used as an etching mask to process the substrate by dry etching, but in reality, there is no dry etching method that can obtain perfect etching selectivity between the photoresist film and the substrate to be processed. Therefore, there is a problem that the photoresist film is also damaged and collapsed during processing of the substrate, and the resist pattern cannot be accurately transferred to the substrate to be processed. Therefore, with the miniaturization of patterns, a higher dry etching resistance has been required for the resist composition. However, on the other hand, in order to increase the resolution, a resin with low light absorption at the exposure wavelength has been required for the resin used in the photoresist composition. Therefore, as the exposure light has become shorter in wavelength from i-line to KrF and ArF, the resin has also changed to novolac resin, polyhydroxystyrene, and resin with an aliphatic polycyclic skeleton, but in reality, the etching speed under dry etching conditions during substrate processing has become faster, and recent photoresist compositions with high resolution tend to have weaker etching resistance.

[0005] For this reason, it has become necessary to dry etch the substrate to be processed using a thinner photoresist film with a weaker etching resistance, and securing the materials and processes for this processing step has become an urgent need.

[0006] One method for solving such problems is the multi-layer resist method, in which a resist intermediate film having etching selectivity different from that of a photoresist film (i.e., a resist upper layer film) is interposed between the resist upper layer film and a substrate to be processed, a pattern is obtained in the resist upper layer film, and then the pattern is transferred to the resist intermediate film by dry etching using the resist upper layer film pattern as a dry etching mask, and the pattern is further transferred to the substrate to be processed by dry etching using the resist intermediate film as a dry etching mask.

[0007] One of the multilayer resist methods is a three-layer resist method that can be performed using a general resist composition used in a single-layer resist method. In this three-layer resist method, for example, an organic film made of novolac resin or the like is formed on a substrate to be processed as a resist underlayer film, a silicon-containing resist intermediate film is formed on the organic film as a resist intermediate film, and a normal organic photoresist film is formed on the organic film as a resist upper layer film. When dry etching is performed using fluorine-based gas plasma, the organic resist upper layer film has a good etching selectivity to the silicon-containing resist intermediate film, so that the resist upper layer film pattern can be transferred to the silicon-containing resist intermediate film by dry etching using fluorine-based gas plasma. According to this method, even if a resist composition that is difficult to form a pattern with a sufficient film thickness for directly processing a substrate to be processed or a resist composition that does not have sufficient dry etching resistance for processing a substrate is used, a pattern can be transferred to the silicon-containing resist intermediate film (resist intermediate film), and then, by performing pattern transfer by dry etching using oxygen-based or hydrogen-based gas plasma, a pattern of an organic film (resist underlayer film) made of novolac resin or the like that has sufficient dry etching resistance for processing a substrate can be obtained. As the above-mentioned resist underlayer film, many films are already known, for example, the one described in Patent Document 1.

[0008] On the other hand, in recent years, the miniaturization of DRAM memories has accelerated, and the need for a resist underlayer film having further improved dry etching resistance and excellent filling and planarization properties has increased. As a coating-type organic underlayer film material having excellent filling and planarization properties, for example, the one described in Patent Document 2 has been reported, but in terms of application to the latest generation, there are concerns about dry etching resistance, and the application limit of conventional coating-type organic underlayer film materials is approaching.

[0009] In response to the above problem, Patent Document 3 reports that the etching resistance during substrate processing is improved by subjecting the resist underlayer film to additional processing such as plasma irradiation or electron beam irradiation. It is believed that the additional processing causes the chemical bonds of the hydrocarbon-containing film to dissociate and recombine, reconstructing the film as a hardened film having a diamond-like carbon structure, thereby contributing to an increase in hardness and density. However, the resist underlayer film used in the above example has a large film thickness change of 100 nm or more due to the additional processing, and it is expected that the film thickness uniformity after the additional processing is also insufficient. When used as a filling film for a substrate to be processed having a step, it is possible that the flatness will deteriorate due to the influence of film shrinkage caused by plasma irradiation and electron beam irradiation, and that voids will occur in the filling film due to excessive scattering of solid components in the film during the plasma irradiation and electron beam irradiation. For this reason, it is considered that a method for forming a resist underlayer film with a small film thickness change before and after plasma irradiation is required. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2004-205685 A [Patent Document 2] Patent No. 6714493 [Patent Document 3] JP 2020-183506 A Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a method for forming a resist underlayer film which, by irradiating with plasma, exhibits extremely superior dry etching resistance compared to conventional organic underlayer film materials and also exhibits excellent film thickness uniformity, and a method for forming a pattern using the resist underlayer film. [Means for solving the problem]

[0012] In order to solve the above problems, the present invention provides A method for forming a resist underlayer film on a substrate, comprising the steps of: (i) coating a composition for forming a resist underlayer film, which comprises (A) a polymer and (B) an organic solvent, on the substrate, and curing the composition by heat treatment at a temperature of 100° C. or higher and 800° C. or lower for 10 to 7,200 seconds to form an underlayer film precursor film; (ii) irradiating the substrate on which the underlayer film precursor film has been formed with plasma to form a resist underlayer film; A method for forming a resist underlayer film, comprising: The present invention provides a method for forming a resist underlayer film, wherein the polymer (A) contains a structural unit represented by the following general formula (1) and has a weight average molecular weight of 2,500 to 20,000 in terms of polystyrene as determined by gel permeation chromatography: [ka] (In the formula, Ar 1 and Ar 2 are independently a substituted or unsubstituted benzene ring or a substituted or unsubstituted naphthalene ring, X is a structure represented by the following general formula (1A), Y is a divalent organic group having 6 to 50 carbon atoms, and k is 0 or 1. [ka] (In the formula, n 1 is 0 or 1, n 2 is 1 or 2, R 2 R is a hydrogen atom, an organic group having 1 to 10 carbon atoms, or a structure represented by the following general formula (1B). 3 is a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, or a group represented by the following general formula (1C), 3 is 0, 1, or 2, * is the bond to the methylene group, and ** is the bond to the quaternary carbon of the fluorene.) [ka] (wherein * represents the bond site to the oxygen atom, R Ais a divalent organic group having 1 to 10 carbon atoms, R B is a hydrogen atom or a monovalent organic group having 1 to 10 carbon atoms. [ka] (In the formula, R 4 is a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms, and the hydrogen atom on the benzene ring in the formula may be substituted with a methyl group or a methoxy group.

[0013] In this resist underlayer film forming method, the structure containing the fluorene skeleton with high carbon density is repeatedly bonded via the methylene group, so that the film is easily modified by plasma irradiation, and a resist underlayer film with excellent dry etching resistance can be provided. In addition, by containing the crosslinking group structure containing oxygen atoms and the methylene group, the hardening property, density, and heat resistance of the resist underlayer film are improved, and the scattering of solid components in the film caused by plasma irradiation can be mitigated, so that the change in film thickness before and after plasma irradiation is small, and a resist underlayer film with high film thickness uniformity and dry etching resistance can be formed.

[0014] In addition, in the general formula (1), Y preferably has any of the structures represented by the following formula (Y-1). [ka] (The hydrogen atoms in the above structure may be substituted with hydroxyl groups or monovalent organic groups having 1 to 10 carbon atoms.)

[0015] According to such a method for forming a resist underlayer film, the film is easily modified by plasma irradiation, and a resist underlayer film having excellent dry etching resistance can be provided.

[0016] In addition, in the general formula (1A), R 2 is preferably a hydrogen atom.

[0017] Such a method for forming a resist underlayer film can provide a resist underlayer film having excellent adhesion to a substrate after plasma exposure, and is also preferable because it contributes to densifying the film.

[0018] In addition, in the general formula (1A), R 2 is a hydrogen atom or a structure represented by the general formula (1B), 2 In the structure constituting the formula (1), when the ratio of hydrogen atoms is a and the ratio of the structure represented by the general formula (1B) is b, it is preferable that the relationship of a+b=1, 0.1≦b≦0.9 is satisfied.

[0019] Such a method for forming a resist underlayer film can provide a resist underlayer film having excellent adhesion to a substrate after plasma exposure, and also provides a polymer having excellent fluidity and therefore excellent planarization properties.

[0020] In addition, in the general formula (1), Ar 1 and Ar 2 is an unsubstituted benzene ring, and in the general formula (1A), it is preferable that n1 is 0, n2 is 1 or 2, and n3 is 0.

[0021] According to such a method for forming a resist underlayer film, since the film is easily modified by plasma irradiation, it is possible to provide a resist underlayer film having excellent dry etching resistance, and since the resulting polymer has excellent fluidity, it is possible to provide a method for forming a resist underlayer film having excellent planarization properties.

[0022] In the general formula (1), k is preferably 0.

[0023] According to such a method for forming a resist underlayer film, a polymer having excellent solvent solubility is obtained, so that the storage stability of the composition for forming a resist underlayer film is improved, and a method for forming a resist underlayer film having excellent practicality can be provided.

[0024] The (A) polymer preferably has a weight average molecular weight in terms of polystyrene measured by gel permeation chromatography of 7,000 to 15,000.

[0025] Such a method for forming a resist underlayer film can improve the curability, density, and heat resistance of the resist underlayer film and can mitigate the scattering of solid components in the film due to plasma exposure, making it possible to form a resist underlayer film that achieves both high film thickness uniformity and high dry etching resistance.

[0026] In addition, it is preferable that the composition for forming a resist underlayer film further contains one or more of (C) a crosslinking agent, (D) a surfactant, (E) an acid generator, and (F) a plasticizer.

[0027] By using a composition for forming a resist underlayer film containing the above additive, it becomes possible to adjust various physical properties required when used to form a resist underlayer film, such as coatability, film thickness uniformity, dry etching resistance, and filling / planarization characteristics, within an appropriate range.

[0028] The (B) organic solvent is preferably a mixture of one or more organic solvents having a boiling point of less than 180°C and one or more (B-1) high boiling point solvents having a boiling point of 180°C or higher.

[0029] By using such a composition for forming a resist underlayer film containing the component (B), a resist underlayer film having excellent planarization properties can be formed.

[0030] In the step (ii), the plasma irradiation is performed using N 2 , N.F. 3 , H 2 It is preferred to carry out the reaction in an atmosphere of a fluorocarbon, a rare gas, or a mixture of any of these.

[0031] By using plasma irradiation as a method for curing the resist underlayer film, it is possible to provide a resist underlayer film that exhibits excellent dry etching resistance compared to a curing method that involves only heating.

[0032] In the step (i), the heat treatment is preferably carried out in an atmosphere having an oxygen concentration of 1% or more and 21% or less.

[0033] By using such a method, the reactive points of the resin in the resist underlayer film can be activated, and the curing reaction caused by the plasma irradiation can be promoted.

[0034] In the step (i), the heat treatment is preferably carried out in an atmosphere having an oxygen concentration of less than 1%.

[0035] This method is useful because it can activate reactive sites of the polymer in the resist underlayer film and promote the curing reaction by plasma irradiation without causing deterioration of the substrate to be processed, even if the substrate to be processed contains a material that is unstable when heated in an oxygen atmosphere.

[0036] The present invention also provides a method for forming a pattern on a substrate to be processed, comprising the steps of: (I-1) forming a resist underlayer film on a substrate to be processed by the above-mentioned method for forming a resist underlayer film; (I-2) forming a resist intermediate film on the resist underlayer film; (I-3) forming a resist upper layer film on the resist intermediate film using a photoresist material; (I-4) a step of forming a pattern on the resist upper layer film by pattern-exposing the resist upper layer film and then developing the resist upper layer film with a developer; (I-5) a step of transferring the pattern to the resist intermediate film by dry etching using the resist upper layer film on which the pattern has been formed as a mask; (I-6) a step of transferring a pattern to the resist underlayer film by dry etching using the resist intermediate film to which the pattern has been transferred as a mask; and (I-7) A step of processing the substrate to be processed using the resist underlayer film on which the pattern has been formed as a mask to form a pattern on the substrate to be processed. The present invention provides a pattern forming method comprising the steps of:

[0037] The above-described pattern forming method makes it possible to form a fine pattern on a workpiece with high precision.

[0038] The present invention also provides a method for forming a pattern on a substrate to be processed, comprising the steps of: (II-1) forming a resist underlayer film on a substrate having a step by the above-mentioned method for forming a resist underlayer film; (II-2) forming a resist top layer film on the resist underlayer film; (II-3) a step of forming a pattern on the resist upper layer film by pattern-exposing the resist upper layer film and then developing the resist upper layer film with a developer; (II-4) a step of transferring the pattern to the resist underlayer film by dry etching using the resist upper layer film on which the pattern has been formed as a mask; (II-5) A step of processing the substrate to be processed using the resist underlayer film on which the pattern has been formed as a mask to form a pattern on the substrate to be processed. The present invention provides a pattern forming method comprising the steps of:

[0039] The above-described pattern forming method makes it possible to form a fine pattern on a workpiece with high precision.

[0040] In this case, it is preferable that the aspect ratio of the step of the substrate to be processed is 3 or more.

[0041] The pattern formation method of the present invention is capable of forming a resist underlayer film having high-level filling / planarization properties, and is therefore particularly useful for microfabrication of substrates having such structures or steps. Effect of the Invention

[0042] As described above, the resist underlayer film forming method and the pattern forming method of the present invention are particularly suitable for use in a multi-layer resist process including filling / flattening a substrate to be processed having steps and irregularities, and are extremely useful in fine patterning for manufacturing semiconductor devices. In particular, in a fine patterning process using a multi-layer resist method in a semiconductor device manufacturing process, even on a substrate to be processed having a portion where filling / flattening is difficult, such as a dense portion of a fine pattern structure with a high aspect ratio, as typified by a DRAM memory that is becoming increasingly finer, filling can be performed without causing defects such as voids or peeling, and a resist underlayer film with excellent flatness characteristics can be formed. In addition, the resist underlayer film shows excellent etching resistance and film thickness uniformity compared to conventional resist underlayer film forming methods, and the effect can be exhibited particularly by plasma irradiation. Therefore, a fine pattern can be formed on a substrate to be processed with even greater precision. [Brief description of the drawings]

[0043] [Figure 1] FIG. 2 is an explanatory diagram of an example (three-layer resist process) of the pattern forming method of the present invention. [Diagram 2] FIG. 1 is an explanatory diagram of a method for evaluating embedding characteristics. [Diagram 3] FIG. 1 is an explanatory diagram of a flattening characteristic evaluation method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] As described above, in a fine patterning process using a multilayer resist method, there has been a demand for the development of a resist underlayer film forming method capable of transferring a resist pattern to a substrate to be processed with higher accuracy, and a pattern forming method using the resist underlayer film.

[0045] Patent Document 3 reports that plasma exposure improves the dry etching resistance of the resist underlayer film during substrate processing. It is believed that plasma exposure causes the carbon bonds in the resist underlayer film to dissociate and recombine, reconstructing the film as a hardened film with a diamond-like carbon structure, which contributes to an increase in hardness and density.

[0046] On the other hand, the resist underlayer film forming composition used in the examples of Patent Document 3 uses an oligomer with a molecular weight of 1,100 or less, and therefore the curability of the resist underlayer film before the additional treatment is insufficient, and not only the dissociation and recombination of carbon bonds progresses, but also the scattering of solid components in the film is actively occurring. In the above examples, the change in film thickness due to plasma irradiation is large at 100 nm or more, and it is expected that the film thickness uniformity of the resist underlayer film after plasma irradiation is also insufficient. When used as a filling film for a substrate to be processed having a step, it is possible that the flatness will deteriorate due to the influence of film shrinkage caused by plasma irradiation and electron beam irradiation, and that voids will occur in the filling film due to excessive scattering of solid components in the film during the plasma irradiation and electron beam irradiation. For this reason, it is considered that a method for forming a resist underlayer film with a small change in film thickness before and after plasma irradiation is required.

[0047] The present inventors have been searching for a method for forming a resist underlayer film that can achieve both high dry etching resistance and film thickness uniformity, and have conducted intensive research. As a result, they have found that a resist underlayer film forming method comprising: coating a composition for forming a resist underlayer film, which comprises a polymer (A) containing a structural unit represented by general formula (1) and an organic solvent (B), and the polymer (A) has a weight average molecular weight in terms of polystyrene of 2,500 to 20,000 as measured by gel permeation chromatography; curing the composition by heat treatment at a temperature of 100°C to 800°C for 10 to 7,200 seconds to form an underlayer film precursor film; and exposing the substrate on which the underlayer film precursor film has been formed to plasma to form a resist underlayer film (cured film), can form a resist underlayer film that has a smaller change in film thickness before and after plasma exposure and exhibits excellent dry etching resistance and film thickness uniformity, compared to the conventional resist underlayer film forming method using plasma exposure, and have completed the present invention.

[0048] The present invention will be described in detail below, but the present invention is not limited thereto.

[0049] <Method for forming resist underlayer film> The present invention is a method for forming a resist underlayer film on a substrate, the method comprising the steps of: (i) coating a composition for forming a resist underlayer film, the composition including (A) a polymer and (B) an organic solvent, onto the substrate, and curing the composition by heat treatment at a temperature of 100° C. or higher and 800° C. or lower for 10 to 7,200 seconds, to form an underlayer film precursor film; and (ii) irradiating the substrate on which the underlayer film precursor film has been formed with plasma to form a resist underlayer film, wherein the (A) polymer includes a constitutional unit represented by the following general formula (1) and has a weight average molecular weight in terms of polystyrene of 2,500 to 20,000 as determined by gel permeation chromatography. [ka] (In the formula, Ar 1 and Ar 2 are independently a substituted or unsubstituted benzene ring or a substituted or unsubstituted naphthalene ring, X is a structure represented by the following general formula (1A), Y is a divalent organic group having 6 to 50 carbon atoms, and k is 0 or 1. [ka] (In the formula, n 1 is 0 or 1, n 2 is 1 or 2, R 2 R is a hydrogen atom, an organic group having 1 to 10 carbon atoms, or a structure represented by the following general formula (1B). 3 is a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, or a group represented by the following general formula (1C), 3 is 0, 1, or 2, * is the bond to the methylene group, and ** is the bond to the quaternary carbon of the fluorene.) [ka] (wherein * represents the bond site to the oxygen atom, R A is a divalent organic group having 1 to 10 carbon atoms, R B is a hydrogen atom or a monovalent organic group having 1 to 10 carbon atoms. [ka] (In the formula, R 4 is a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms, and the hydrogen atom on the benzene ring in the formula may be substituted with a methyl group or a methoxy group.

[0050] The method for coating the composition for forming a resist underlayer film in the above step (i) is not particularly limited. The details of the composition for forming a resist underlayer film will be described later.

[0051] In the above step (i), the heat treatment (baking) temperature of the coating film is from 100° C. to 800° C., preferably from 150° C. to 600° C., more preferably from 150° C. to 400° C., and even more preferably from 200° C. to 350° C. The baking time is in the range of 10 seconds to 7,200 seconds, more preferably from 30 seconds to 600 seconds.

[0052] By adjusting the baking temperature and time appropriately within the above range, it is possible to obtain planarization and filling characteristics suitable for the application, as well as hardening characteristics such as dry etching resistance and heat resistance. By performing heat treatment (baking) within the temperature range of 150°C to 400°C, the film contains many active sites where carbon bonds in the underlayer film precursor film are dissociated and recombined, which makes it easier to promote film modification by plasma irradiation, and therefore a resist underlayer film with excellent dry etching resistance can be formed. At a baking temperature of 100°C or higher, the residual solvent in the film can be reduced, and deterioration of film thickness uniformity due to plasma irradiation can be suppressed. At a baking temperature of 800°C or lower, thermal decomposition of the base resin can be suppressed, and a resist underlayer film with a small amount of sublimation can be provided. It is also possible to perform the heating treatment in multiple steps (step baking).

[0053] In the above step (i), the heat treatment can be carried out in an atmosphere having an oxygen concentration of 1% or more and 21% or less.

[0054] By using such a method, the reactive sites of the resin in the resist underlayer film precursor film can be activated, and the curing reaction caused by the plasma irradiation can be promoted.

[0055] Alternatively, in the above step (i), the heat treatment can be carried out in an atmosphere with an oxygen concentration of less than 1%.

[0056] The atmosphere during baking can be selected as necessary from either an oxygen-containing atmosphere such as air (oxygen concentration 1% to 21%) or an oxygen-free atmosphere such as nitrogen. For example, if the substrate to be processed is susceptible to air oxidation, substrate damage can be suppressed by forming a hardened film by performing heat treatment in an atmosphere with an oxygen concentration of less than 1%.

[0057] The plasma irradiation can be performed by a known method, for example, the method described in Japanese Patent No. 5746670, "Improvement of the wiggling profile of spin-on carbon hard mask by H2 plasma treatment" (J.Vac.Sci.Technol. B26 (1), Jan / Feb 2008, p67-71).

[0058] The RF discharge power is preferably 100 to 10,000 W, and more preferably 500 to 5,000 W.

[0059] The gas atmosphere is, for example, N 2 , N.F. 3 , H 2 , rare gases such as He, and fluorocarbons; more preferably He, Ar, N 2 , Ne, NF 3 , H 2 , C.F. 4 , CHF 3 , C.H. 2 F 2 , C.H. 3 F, C 4 F 6 , C 4 F 8 These gases may be used in combination of two or more.2 It is an advantage of the present invention that the effect of the present invention can be expected even when a gas atmosphere not containing

[0060] The plasma irradiation time can be selected from the range of, for example, 10 to 240 seconds, and the pressure can be appropriately selected.

[0061] In the above step (ii), the plasma irradiation is performed with N 2 , N.F. 3 , H 2 It is preferable to carry out the reaction under an atmosphere of a fluorocarbon, a rare gas such as He, or a mixture of any of these.

[0062] From the viewpoint of productivity, the most preferable gas atmospheres are He, Ar, and N 2 , H 2 etc.

[0063] After the plasma irradiation, the resist underlayer film may be subjected to a heat treatment. When heating after the plasma irradiation, the heating conditions can be appropriately selected from the range of a heating temperature of 80 to 800°C (preferably 100 to 700°C, more preferably 200 to 600°C) and a heating time of 30 to 180 seconds (preferably 30 to 120 seconds). Without being bound by theory, it is believed that high-temperature heating after the plasma irradiation can bond dangling bonds and contribute to densification of the cured film (resist underlayer film).

[0064] The atmosphere during heating after plasma irradiation can be selected as necessary from either an oxygen-containing atmosphere such as air (oxygen concentration 1% to 21%) or an oxygen-free atmosphere such as nitrogen. For example, if the substrate to be processed is susceptible to air oxidation, substrate damage can be suppressed by forming a hardened film by performing heat treatment in an atmosphere with an oxygen concentration of less than 1%.

[0065] The irradiation device is not particularly limited as long as it is capable of irradiating plasma, and for example, Telius SP and Tactras Vigus manufactured by Tokyo Electron Co., Ltd. can be used. It is possible to select the device and set the conditions so that the effect of the present invention can be more significantly exhibited.

[0066] In the pattern forming method of the present invention using the resist underlayer film forming composition described in detail below, it is preferable to use a substrate to be processed having a structure or step with an aspect ratio of 3 or more or a height of 30 nm. The resist underlayer film forming composition used in the present invention has excellent filling / flattening properties, so that even if the substrate to be processed has a structure or step (unevenness) with an aspect ratio of 3 or more or a height of 30 nm or more, a flat resist underlayer film (cured film) can be formed. The structure of the substrate to be processed preferably has an aspect ratio of 3 or more, and more preferably has an aspect ratio of 5 or more. The height of the structure or step of the substrate to be processed is preferably 30 nm or more, more preferably 50 nm or more, and more preferably 100 nm or more. In a method for processing a stepped substrate having a pattern with the above aspect ratio and height, by forming a resist underlayer film using the resist underlayer film formation method of the present invention and performing filling / planarization, it becomes possible to make the film thicknesses of the resist intermediate film and resist top layer film formed thereafter uniform, which makes it easier to ensure the exposure depth margin (DOF) during photolithography, and is therefore highly preferable.

[0067] <Composition for forming resist underlayer film> The method for forming a resist underlayer film of the present invention uses a composition for forming a resist underlayer film containing (A) a polymer and (B) an organic solvent, and is characterized in that the polymer (A) contains a constitutional unit represented by the following general formula (1) and has a weight average molecular weight of 2,500 to 20,000 in terms of polystyrene, as determined by a gel permeation chromatography method: [ka] (In the formula, Ar 1 and Ar 2are independently a substituted or unsubstituted benzene ring or a substituted or unsubstituted naphthalene ring, X is a structure represented by the following general formula (1A), Y is a divalent organic group having 6 to 50 carbon atoms, and k is 0 or 1. [ka] (In the formula, n 1 is 0 or 1, n 2 is 1 or 2, R 2 R is a hydrogen atom, an organic group having 1 to 10 carbon atoms, or a structure represented by the following general formula (1B). 3 is a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, or a group represented by the following general formula (1C), 3 is 0, 1, or 2, * is the bond to the methylene group, and ** is the bond to the quaternary carbon of the fluorene.) [ka] (wherein * represents the bond site to the oxygen atom, R A is a divalent organic group having 1 to 10 carbon atoms, R B is a hydrogen atom or a monovalent organic group having 1 to 10 carbon atoms. [ka] (In the formula, R 4 is a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms, and the hydrogen atom on the benzene ring in the formula may be substituted with a methyl group or a methoxy group.

[0068] [(A) Polymer (resin)] If the (A) polymer is a resin containing a structural unit represented by the above general formula (1), a structure containing a high carbon density fluorene skeleton is repeatedly bonded via a methylene group, so that dissociation and recombination of carbon bonds is easily promoted by plasma irradiation, and a resist underlayer film having a diamond-like carbon structure can be formed. In addition, by containing a crosslinking group structure containing an oxygen atom and a methylene group, the hardening property, density, and heat resistance of the resist underlayer film are improved, and scattering of solid components in the film due to plasma irradiation can be mitigated, so that a resist underlayer film that highly balances film thickness uniformity and dry etching resistance can be formed.

[0069] In the above general formula (1B), R A Examples of the divalent organic group having 1 to 10 carbon atoms represented by the formula (1) include alkanediyl groups such as a methylene group, an ethanediyl group, a propanediyl group, a butanediyl group, a pentanediyl group, a hexanediyl group, an octanediyl group, and a decanediyl group, and arenediyl groups such as a benzenediyl group, a methylbenzenediyl group, and a naphthalenediyl group.

[0070] In the above general formula (1B), R B Examples of the monovalent organic group having 1 to 10 carbon atoms represented by the formula (1) include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a sec-butyl group, a t-butyl group, an n-pentyl group, an n-hexyl group, an n-octyl group, and an n-decyl group, and aryl groups such as a phenyl group, a tolyl group, a xylyl group, a mesityl group, and a naphthyl group.

[0071] A part or all of the hydrogen atoms of the alkanediyl group, arenediyl group, alkyl group, aryl group and the like may be substituted. Examples of the substituent include alkoxy groups such as methoxy group, ethoxy group, n-propoxy group, i-propoxy group, n-butoxy group, i-butoxy group, sec-butoxy group, t-butoxy group, n-pentyloxy group, and n-hexyloxy group; and alkoxycarbonyl groups such as methoxycarbonyl group, ethoxycarbonyl group, n-propoxycarbonyl group, i-propoxycarbonyl group, n-butoxycarbonyl group, i-butoxycarbonyl group, sec-butoxycarbonyl group, t-butoxycarbonyl group, n-pentyloxycarbonyl group, and n-hexyloxycarbonyl group.

[0072] A particularly preferred example is the structure represented by the following formula (1D). When the compound has such a structure, the thermal fluidity is good, and a resist underlayer film material having excellent filling / flattening properties can be provided. In addition, the heat resistance and film formability are good, and the generation of sublimates during heat curing is suppressed, the contamination of the device due to the sublimates is suppressed, and the occurrence of coating defects can be suppressed. [ka] (In the above formula, * represents the bonding site to the oxygen atom.)

[0073] In the above formula (1), Y is preferably any of the structures represented by the following formula (Y-1): In the following structures, the position of the bond to the methylene group in formula (1) is not particularly limited. [ka] (The hydrogen atoms in the above structure may be substituted with hydroxyl groups or monovalent organic groups having 1 to 10 carbon atoms.)

[0074] By using a polymer containing the above structure, the carbon density in the resist underlayer film is improved, and therefore, dissociation and recombination of carbon bonds is easily promoted by plasma irradiation, making it possible to form a resist underlayer film having a diamond-like carbon structure.

[0075] The hydrogen atoms in the above structure may be substituted with hydroxyl groups or monovalent organic groups having 1 to 10 carbon atoms. Examples of the monovalent organic groups having 1 to 10 carbon atoms include linear, branched or cyclic alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 10 carbon atoms, or groups represented by the following general formula (Y-2). [ka] (In the formula, * represents a bonding site with the structure of formula (Y-1), and R A is a divalent organic group having 1 to 10 carbon atoms, R B is a hydrogen atom or a monovalent organic group having 1 to 10 carbon atoms, and s is 0 or 1.

[0076] From the viewpoint of dry etching resistance, it is more preferable that the hydrogen atoms in the structure represented by the above formula (Y-1) are unsubstituted.

[0077] More preferred examples of the structure represented by the above formula (Y-1) include the following structures. [ka]

[0078] In the above formula (1C), R 4 is preferably a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms including an ethenyl group or an ethynyl group, and the hydrogen atom on the benzene ring is preferably unsubstituted.

[0079] Above R 4 When R is a hydrogen atom, the curability of the polymer can be further improved, and the film thickness uniformity after plasma exposure can be further improved. 4 When is an ethenyl group or an ethynyl group-containing hydrocarbon group having 1 to 10 carbon atoms, the fluidity of the polymer can be further improved, and the flattening properties after plasma exposure can be further improved.

[0080] In the above formula (1), Ar 1 and Ar 2It is preferable that n1 is an unsubstituted benzene ring or an unsubstituted naphthalene ring, n2 is 1, and n3 is 0.

[0081] In addition, in the above formula (1), Ar 1 and Ar 2 is an unsubstituted benzene ring, and in the above formula (1A), it is more preferable that n1 is 0, n2 is 1 or 2, and n3 is 0.

[0082] In a method for forming a resist underlayer film using a composition for forming a resist underlayer film containing such a polymer, dissociation and recombination of carbon bonds is easily promoted by plasma irradiation, making it possible to form a resist underlayer film having a diamond-like carbon structure.

[0083] In addition, by including a crosslinking group structure containing an oxygen atom, the curability, density, and heat resistance of the resist underlayer film are improved, and a resist underlayer film with excellent film thickness uniformity before and after plasma irradiation can be formed. On the other hand, the fewer the crosslinking group structures containing an oxygen atom, the fewer the oxygen atoms remaining in the film, which is preferable from the viewpoint of etching resistance. For this reason, n2 is more preferably 1, and n3 is more preferably 0.

[0084] In the above formula (1A), k is preferably 0.

[0085] According to such a method for forming a resist underlayer film, a polymer having excellent solvent solubility is obtained, so that the storage stability of the composition for forming a resist underlayer film is improved, and a method for forming a resist underlayer film having excellent practicality can be provided.

[0086] A specific example of a preferred structure is the following structure (1-A1), but is not limited thereto.

[0087] [ka] (In the above formula, R 2 is the same as the above formula (1A).

[0088] In the above formula (1A), n1 is more preferably 0.

[0089] In the case of a method for forming a resist underlayer film using a composition for forming a resist underlayer film containing such a polymer, since a structure containing a fluorene skeleton with high carbon density is repeatedly bonded via a methylene group, dissociation and recombination of carbon bonds are easily promoted by plasma irradiation, and a resist underlayer film having a diamond-like carbon structure can be formed. In addition, since the polymer has excellent fluidity, a method for forming a resist underlayer film having excellent planarization properties can be provided.

[0090] In the above formula (1A), R 2 is more preferably a hydrogen atom or a structure represented by general formula (1B) from the viewpoint of curability.

[0091] By including the above crosslinking group structure, the curability and heat resistance of the resist underlayer film are improved, and a resist underlayer film having excellent film thickness uniformity before and after plasma exposure can be formed.

[0092] In the above formula (1A), R 2 is a hydrogen atom or a structure represented by general formula (1B), 2 In the structure constituting the above, when the ratio of hydrogen atoms is a and the ratio of the structure represented by the general formula (1B) is b, it is preferable to use a polymer that satisfies the relationship of a+b=1, 0.1≦b≦0.9.

[0093] By controlling the ratio of hydrogen atoms to the above general formula (1B) within the above range, it is possible to provide a resist underlayer film material with high fluidity and substrate adhesion, and improved filling / planarization properties. If the range of b is ≦0.9, the content of hydroxyl groups is sufficient, and adhesion to the substrate is good. In addition, crosslinking reactions between hydroxyl groups are preferable for forming a dense film, and it is also preferable to contain a certain proportion of hydroxyl groups from the viewpoint of heat resistance. On the other hand, if the range of b is 0.1≦, the thermal fluidity of the resin is sufficient, and filling / planarization properties are good.

[0094] In the above formula (1A), R2 It is more preferable that is a hydrogen atom.

[0095] In the resist underlayer film forming method using the composition for forming the resist underlayer film containing such a polymer, dissociation and recombination of carbon bonds are easily promoted by plasma irradiation, and a resist underlayer film having a diamond-like carbon structure can be formed. In addition, since the curability, density, and heat resistance of the resist underlayer film are improved, a resist underlayer film having a small change in film thickness before and after plasma irradiation and excellent film thickness uniformity after plasma irradiation can be formed.

[0096] The weight average molecular weight of the polymer (A) in terms of polystyrene as determined by gel permeation chromatography is 2,500 to 20,000, preferably 5,000 to 18,000, and more preferably 7,000 to 15,000. When it is 2,500 or more, the amount of sublimation can be suppressed, and deterioration of the film thickness uniformity can be suppressed. When it is 20,000 or less, the solvent solubility of the resin can be maintained and precipitation over time can be prevented, which is preferable from the viewpoint of storage stability. In addition, since the fluidity is excellent, excellent embedding properties and excellent flatness can be realized. And, outgassing during baking can be suppressed without impairing the solubility of the polymer in organic solvents.

[0097] The polydispersity (Mw / Mn) of the polymer (A) is preferably in the range of 1.2 to 12, but narrowing the molecular weight distribution by cutting out monomer components, oligomer components, or low molecular weight components with a molecular weight (Mw) of 1,100 or less increases crosslinking efficiency, and by suppressing volatile components during baking and plasma exposure, a resist underlayer film with excellent film thickness uniformity can be formed. By suppressing volatile components during baking, contamination around the bake cup can also be prevented. Note that Mn represents the number average molecular weight.

[0098] The polymer (A) may contain the structural unit of the formula (1) above, and may also be copolymerized with other copolymerizable monomers (A-2). Specific examples of the monomers include phenol, o-cresol, m-cresol, p-cresol, 2,3-dimethylphenol, 2,5-dimethylphenol, 3,4-dimethylphenol, 3,5-dimethylphenol, 2,4-dimethylphenol, 2,6-dimethylphenol, 2,3,5-trimethylphenol, 3,4,5-trimethylphenol, 2-t-butylphenol, 3-t-butylphenol, 4-t-butylphenol, 2-phenylphenol, 3-phenylphenol, 4-phenylphenol, 3,5-diphenylphenol, 2-naphthylphenol, 3-naphthylphenol, 4-naphthylphenol, 4-tritylphenol, resorcinol, 2-methylresorcinol, 4-methylresorcinol, 5-methylresorcinol, catechol, 4-t-butylcatechol, 2-methoxyphenol, 3-methoxyphenol, 2-propylphenol, phenol, 3-propylphenol, 4-propylphenol, 2-isopropylphenol, 3-isopropylphenol, 4-isopropylphenol, 2-methoxy-5-methylphenol, 2-t-butyl-5-methylphenol, pyrogallol, thymol, isothymol, 1-naphthol, 2-naphthol, 2-methyl-1-naphthol, 4-methoxy-1-naphthol, 7-methoxy-2-naphthol, and 1,5-dihydroxynaphthalene, 1,7-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, Examples of the monomer include dihydroxynaphthalenes such as hydroxynaphthalene, 3-hydroxy-naphthalene-2-methyl carboxylate, indene, hydroxyindene, benzofuran, hydroxyanthracene, acenaphthylene, biphenyl, bisphenol, trisphenol, dicyclopentadiene, tetrahydroindene, 4-vinylcyclohexene, norbornadiene, 5-vinylnorborn-2-ene, α-pinene, β-pinene, and limonene. Copolymers of ternary or higher monomers containing these monomers may also be used.

[0099] When the (A) polymer contains a constituent unit derived from another monomer (A-2), the ratio of the constituent unit of the above formula (1) to the constituent unit derived from the other monomer (A-2) preferably satisfies the relationship c+d=1, 0.5≦c≦0.9, and 0.1≦d≦0.5, where c is the constituent unit of the above formula (1) and d is the constituent unit derived from the other monomer (A-2).

[0100] By including a structural unit derived from the other monomer (A-2), it is possible to appropriately adjust the coatability, film thickness uniformity, filling characteristics, planarization characteristics, and dry etching resistance of the resist underlayer film. However, in order to form a resist underlayer film having good dry etching resistance after plasma exposure, a polymer containing a large amount of the structural unit of the above formula (1) is preferable, and a polymer not containing a structural unit derived from the other monomer (A-2) is more preferable.

[0101] The blending ratio of the polymer (A) in the composition for forming a resist underlayer film is not particularly limited, but can be, for example, 1 to 50 parts by mass, preferably 1 to 20 parts by mass, and more preferably 1 to 10 parts by mass, per 100 parts by mass of the total amount of the composition.

[0102] The polymer (A) may contain a resin having the structural unit of the above formula (1), and may further be blended with another compound or polymer. The blending compound or blending polymer is mixed with a resin having the structural unit represented by the above general formula (1) and plays a role in improving the film-forming properties of spin coating and the embedding properties of a substrate having a step. In addition, the blending compound or blending polymer is preferably a compound having a phenolic hydroxyl group.

[0103] Such materials include phenol, o-cresol, m-cresol, p-cresol, 2,3-dimethylphenol, 2,5-dimethylphenol, 3,4-dimethylphenol, 3,5-dimethylphenol, 2,4-dimethylphenol, 2,6-dimethylphenol, 2,3,5-trimethylphenol, 3,4,5-trimethylphenol, 2-tert-butylphenol, 3-tert-butylphenol, 4-tert-butylphenol, 2-phenylphenol, 3-phenylphenol, 4-phenylphenol, 3,5- Diphenylphenol, 2-naphthylphenol, 3-naphthylphenol, 4-naphthylphenol, 4-tritylphenol, resorcinol, 2-methylresorcinol, 4-methylresorcinol, 5-methylresorcinol, catechol, 4-tert-butylcatechol, 2-methoxyphenol, 3-methoxyphenol, 2-propylphenol, 3-propylphenol, 4-propylphenol, 2-isopropylphenol, 3-isopropylphenol, 4-isopropylphenol, 2-methoxy-5-methylphenol, 2-tert-Butyl-5-methylphenol, pyrogallol, thymol, isothymol, 4,4'-(9H-fluoren-9-ylidene)bisphenol, 2,2'dimethyl-4,4'-(9H-fluoren-9-ylidene)bisphenol, 2,2'diallyl-4,4'-(9H-fluoren-9-ylidene)bisphenol, 2,2'difluoro-4,4'-(9H-fluoren-9-ylidene)bisphenol, 2,2'diphenyl-4,4'-(9H-fluoren-9-ylidene)bisphenol, 2,2'dimethoxy-4,4'-(9H- fluoren-9-ylidene) bisphenol, 2,3,2',3'-tetrahydro-(1,1')-spirobiindene-6,6'-diol, 3,3,3',3'-tetramethyl-2,3,2',3'-tetrahydro-(1,1')-spirobiindene-6,6'-diol, 3,3,3',3',4,4'-hexamethyl-2,3,2',3'-tetrahydro-(1,1')-spirobiindene-6,6'-diol, 2,3,2',3'-tetrahydro-(1,1')-spirobiindene-5,5'-diol, 5,5'-dimethyl-3,3,3',3'-tetramethyl-2,3,2',3'-tetrahydro-(1,1')-spirobiindene-6,6'-diol, 1-naphthol, 2-naphthol, 2-methyl-1-naphthol, 4-methoxy-1-naphthol, 7-methoxy-2-naphthol, dihydroxynaphthalenes such as 1,5-dihydroxynaphthalene, 1,7-dihydroxynaphthalene, and 2,6-dihydroxynaphthalene, 3-hydroxynaphthalene-2-methyl carboxylate, indene, hydroxyindene, benzofuran, hydroxyanthracene, acenaphthylene, and biphenyl. Examples of the novolak resins include bisphenol, trisphenol, dicyclopentadiene, tetrahydroindene, 4-vinylcyclohexene, norbornadiene, 5-vinylnorborn-2-ene, α-pinene, β-pinene, and limonene; polyhydroxystyrene, polystyrene, polyvinylnaphthalene, polyvinylanthracene, polyvinylcarbazole, polyindene, polyacenaphthylene, polynorbornene, polycyclodecene, polytetracyclododecene, polynortricyclene, poly(meth)acrylate, and copolymers thereof. In addition, naphthol dicyclopentadiene copolymers described in JP-A-2004-205685, fluorene bisphenol novolac resins described in JP-A-2005-128509, acenaphthylene copolymers described in JP-A-2005-250434, fullerenes having phenol groups described in JP-A-2006-227391, bisphenol compounds and novolac resins thereof described in JP-A-2006-293298, novolac resins of adamantanephenol compounds described in JP-A-2006-285095, bisnaphthol compounds and novolac resins thereof described in JP-A-2010-122656, and fullerene resin compounds described in JP-A-2008-158002 can also be blended.

[0104] The blending amount of the blending compound or blending polymer is preferably 5 to 100 parts by mass, and more preferably 5 to 50 parts by mass, per 100 parts by mass of the (A) polymer (resin having a structural unit represented by the above general formula (1)).

[0105] In order to form a resist underlayer film having good resistance to dry etching after plasma exposure, it is preferable that the blending amount of the blending compound or blending polymer is small, and it is more preferable that the blending compound or blending polymer is not included.

[0106] [(B) Organic solvent] The organic solvent that can be used in the composition for forming a resist underlayer film is not particularly limited as long as it can dissolve the polymer (A), and is preferably one that can also dissolve the crosslinking agent, surfactant, acid generator, and plasticizer described below.

[0107] Specifically, for example, the solvents described in paragraphs

[0091] to

[0092] of JP 2007-199653 A can be added. More specifically, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, 2-heptanone, cyclopentanone, cyclohexanone, γ-butyrolactone, or a mixture containing one or more of these is preferably used.

[0108] The amount of the organic solvent to be added is desirably adjusted depending on the set film thickness of the resist underlayer film, but is usually within the range of 100 to 50,000 parts by mass per 100 parts by mass of the polymer (A).

[0109] [(B-1) High boiling point solvent] In addition, in the above-mentioned composition for forming a resist underlayer film, the (B) organic solvent may be used as a mixture of one or more organic solvents having a boiling point of less than 180 degrees and one or more organic solvents having a boiling point of 180 degrees or more (hereinafter referred to as "(B-1) high boiling point solvent").

[0110] Specific examples of organic solvents having a boiling point of less than 180 degrees include propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, 2-heptanone, cyclopentanone, and cyclohexanone.

[0111] The (B-1) high boiling point solvent is not particularly limited as long as it can dissolve each component of the composition for forming a resist underlayer film used in the present invention, and may be, for example, a hydrocarbon, an alcohol, a ketone, an ester, an ether, or a chlorine-based solvent. Specific examples include 1-octanol, 2-ethylhexanol, 1-nonanol, 1-decanol, 1-undecanol, ethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, 2,4-pentanediol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, 2,4-heptanediol, 2-ethyl-1,3-Hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, glycerin, n-nonyl acetate, monohexyl ether, ethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monohexyl ether, diethylene glycol monophenyl ether, diethylene glycol monobenzyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol butyl methyl ether, triethylene glycol dimethyl ether, triethylene glycol monomethyl ether, triethylene glycol-n-butyl ether, triethylene glycol butyl methyl ether, tetraethylene glycol dimethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-n-butyl ether, tripropylene glycol dimethyl ether, tripropylene glycol monomethyl ether, tripropylene glycol mono-n-propyl ether, tripropylene glycol mono-n-butyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, triacetin, propylene glycol diacetate, dipropylene glycol methyl-n-propyl ether, dipropylene glycol methyl ether acetate, 1,4-butanediol diacetate, 1,3-butylene glycol diacetate, 1,Examples of the diethyl ester include 6-hexanediol diacetate, triethylene glycol diacetate, γ-butyrolactone, methyl benzoate, ethyl benzoate, propyl benzoate, butyl benzoate, dihexyl malonate, diethyl succinate, dipropyl succinate, dibutyl succinate, dihexyl succinate, dimethyl adipate, diethyl adipate, and dibutyl adipate, and these may be used alone or in combination.

[0112] The (B-1) high boiling point solvent may be appropriately selected from the above, for example, according to the temperature at which the composition for forming a resist underlayer film is heat-treated. The (B-1) high boiling point solvent preferably has a boiling point of 180°C to 300°C, more preferably 200°C to 300°C. If the boiling point is so low, there is no risk of the solvent volatilizing too quickly during baking (heat treatment), and sufficient thermal fluidity can be obtained during film formation. In addition, if the boiling point is so high, there is no risk of the solvent remaining in the film without volatilizing even after baking, and therefore there is no risk of adversely affecting the film properties such as etching resistance.

[0113] When the high boiling point solvent (B-1) is used, the blending amount is preferably 1 to 200 parts by mass, and more preferably 1 to 100 parts by mass, per 100 parts by mass of the polymer (A). Such a blending amount is preferable because there is no risk of the blending amount being too small to impart sufficient thermal fluidity during baking, or the blending amount being too large to remain in the film and lead to deterioration of film properties such as etching resistance.

[0114] [(C) Crosslinking agent] A crosslinking agent (C) can also be added to the composition for forming a resist underlayer film in order to enhance curability and improve dry etching resistance.

[0115] Specifically, the crosslinking agent (C) is preferably a compound having a structure represented by the following general formula (C-1). [ka] (In the above general formula (C-1), W 1 and W 2 each represents a benzene ring or a naphthalene ring which may have a substituent, and R 2 represents a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms, and X is any of the groups represented by the following general formula (2): [ka] (In the formula, * represents a binding site.)

[0116] By including the above-mentioned (C) crosslinking agent, the crosslink density and hardness of the resist underlayer film can be further improved without deteriorating the dry etching resistance of the composition for forming a resist underlayer film.

[0117] The ratio Mw / Mn of the weight average molecular weight Mw and the number average molecular weight Mn of the (C) crosslinking agent, calculated as polystyrene, by gel permeation chromatography, is preferably 1.00≦Mw / Mn≦1.25.

[0118] When the molecular weight dispersity of the crosslinking agent is as described above, the thermal fluidity of the composition for forming a resist underlayer film is good, and therefore when the crosslinking agent is blended into a resist underlayer film material, not only can the fine structure formed on the substrate be well embedded, but also a resist underlayer film that flattens the entire substrate can be formed.

[0119] Other (C) crosslinking agents are not particularly limited, and various known crosslinking agents can be widely used. Examples include melamine-based crosslinking agents, glycoluril-based crosslinking agents, benzoguanamine-based crosslinking agents, urea-based crosslinking agents, β-hydroxyalkylamide-based crosslinking agents, isocyanurate-based crosslinking agents, aziridine-based crosslinking agents, oxazoline-based crosslinking agents, epoxy-based crosslinking agents, and phenol-based crosslinking agents (e.g., methylol or alkoxymethyl-type crosslinking agents of polynuclear phenols).

[0120] Specific examples of the melamine-based crosslinking agent include hexamethoxymethylated melamine, hexabutoxymethylated melamine, alkoxy and / or hydroxyl-substituted derivatives thereof, and partial self-condensates thereof. Specific examples of the glycoluril-based crosslinking agent include tetramethoxymethylated glycoluril, tetrabutoxymethylated glycoluril, alkoxy and / or hydroxyl-substituted derivatives thereof, and partial self-condensates thereof. Specific examples of the benzoguanamine-based crosslinking agent include tetramethoxymethylated benzoguanamine, tetrabutoxymethylated benzoguanamine, alkoxy and / or hydroxyl-substituted derivatives thereof, and partial self-condensates thereof. Specific examples of the urea-based crosslinking agent include dimethoxymethylated dimethoxyethyleneurea, alkoxy and / or hydroxyl-substituted derivatives thereof, and partial self-condensates thereof. Specific examples of the β-hydroxyalkylamide-based crosslinking agent include N,N,N',N'-tetra(2-hydroxyethyl)adipic acid amide. Specific examples of the isocyanurate crosslinking agent include triglycidyl isocyanurate and triallyl isocyanurate.Specific examples of the aziridine crosslinking agent include 4,4'-bis(ethyleneiminocarbonylamino)diphenylmethane and 2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate]. Specific examples of the oxazoline crosslinking agent include 2,2'-isopropylidenebis(4-benzyl-2-oxazoline), 2,2'-isopropylidenebis(4-phenyl-2-oxazoline), 2,2'-isopropylidenebis(4-phenyl-2-oxazoline), 2,2'-methylenebis-4,5-diphenyl-2-oxazoline, 2,2'-methylenebis-4-phenyl-2-oxazoline, 2,2'-methylenebis-4-tertbutyl-2-oxazoline, 2,2'-bis(2-oxazoline), 1,3-phenylenebis(2-oxazoline), 1,4-phenylenebis(2-oxazoline), and 2-isopropenyloxazoline copolymer.Specific examples of epoxy crosslinking agents include diglycidyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, poly(glycidyl methacrylate), trimethylolethane triglycidyl ether, trimethylolpropane triglycidyl ether, and pentaerythritol tetraglycidyl ether.

[0121] Specific examples of polynuclear phenol-based crosslinking agents include compounds represented by the following general formula (C-2). [ka] (In the formula, Q is a single bond or a q-valent hydrocarbon group having 1 to 20 carbon atoms. R 3 is a hydrogen atom or a methyl group. q is an integer of 1 to 5.

[0122] In the above general formula (C-2), Q is a single bond or a q-valent hydrocarbon group having 1 to 20 carbon atoms. q is an integer of 1 to 5, and more preferably 2 or 3. When Q is a q-valent hydrocarbon group having 1 to 20 carbon atoms, Q is a q-valent hydrocarbon group obtained by removing q hydrogen atoms from a hydrocarbon having 1 to 20 carbon atoms. In this case, more specific examples of the hydrocarbon having 1 to 20 carbon atoms include methane, ethane, propane, butane, isobutane, pentane, cyclopentane, hexane, cyclohexane, methylpentane, methylcyclohexane, dimethylcyclohexane, trimethylcyclohexane, benzene, toluene, xylene, ethylbenzene, ethylisopropylbenzene, diisopropylbenzene, methylnaphthalene, ethylnaphthalene, and eicosane.

[0123] R in the above general formula (C-2) 3 is a hydrogen atom or a methyl group, and is preferably a methyl group.

[0124] By using the compound represented by the general formula (C-2) as the crosslinking agent (C), it is possible to improve the denseness of the film, which in turn makes it possible to further improve the heat resistance of the composition for forming a resist underlayer film.

[0125] Specific examples of the compound represented by the above general formula (C-2) include, but are not limited to, the following compounds. 3 is the same as above. q=3 and R 3 From the viewpoints of curability, improvement of film thickness uniformity, and reduction of sublimate, it is preferable that the methyl group is satisfied, and in particular, hexamethoxymethylated products of triphenolmethane, triphenolethane, 1,1,1-tris(4-hydroxyphenyl)ethane, and tris(4-hydroxyphenyl)-1-ethyl-4-isopropylbenzene are preferred.

[0126] [ka]

[0127] [ka]

[0128] The above (C) crosslinking agent can be used alone or in combination of two or more. The content of the (C) crosslinking agent is preferably 5 parts by mass to 100 parts by mass, more preferably 10 parts by mass to 50 parts by mass, relative to 100 parts by mass of the above (A) polymer. When the added amount is 5 parts by mass or more, the crosslinking reaction with the (A) polymer is promoted, and a dense film with excellent curability is formed, so that a resist underlayer film with good heat resistance, dry etching resistance, and film thickness uniformity can be formed. On the other hand, when the added amount is 100 parts by mass or less, the generation of sublimates due to the slowdown of the crosslinking reaction between the (A) polymer and the (C) crosslinking agent can be suppressed, and the generation of sublimates and the deterioration of film thickness uniformity can be reduced.

[0129] [(D) Surfactant] The resist underlayer film forming composition may contain a surfactant (D) to improve the coating property in spin coating. For example, the surfactants described in JP-A-2009-269953, paragraphs

[0142] to

[0147] may be used. The amount of the surfactant added is preferably 0.001 to 20 parts by mass, more preferably 0.01 to 10 parts by mass, based on 100 parts by mass of the polymer (A).

[0130] [(E) Acid generator] The resist underlayer film forming composition may generate an acid by thermal decomposition or by light irradiation, and any of them may be added.Specifically, the materials described in paragraphs

[0061] to

[0085] of JP2007-199653A may be added, but are not limited thereto.

[0131] The acid generators may be used alone or in combination of two or more. When an acid generator is added, the amount of the acid generator added is preferably 0.05 to 50 parts by mass, more preferably 0.1 to 10 parts by mass, based on 100 parts by mass of the polymer (A).

[0132] [(F) Plasticizer] In addition, the composition for forming a resist underlayer film may contain a plasticizer (F) in order to further improve the thermal fluidity. The plasticizer is not particularly limited, and various known plasticizers may be widely used. Examples of the plasticizer include low molecular weight compounds such as phthalates, adipic esters, phosphates, trimellitates, and citrates, and polymers such as polyethers, polyesters, and polyacetal polymers described in JP-A-2013-253227. When a plasticizer is added, the amount of the plasticizer is preferably 5 to 500 parts by mass, more preferably 10 to 200 parts by mass, relative to 100 parts by mass of the polymer (A).

[0133] In addition to the above, the resist underlayer film forming composition may contain an additive (flow promoter) for further improving the thermal flowability. The additive is not particularly limited as long as it contributes to improving the thermal flowability and imparts filling and flattening properties, but for example, a liquid additive having a polyethylene glycol or polypropylene glycol structure, or a thermally decomposable polymer having a weight loss rate of 40% or more between 30°C and 250°C and a weight average molecular weight of 300 to 200,000 is preferably used. This thermally decomposable polymer preferably contains a repeating unit having an acetal structure represented by the following general formula (DP1) or (DP1a).

[0134] [ka] (In the formula, R 6 is a hydrogen atom or an optionally substituted saturated or unsaturated monovalent organic group having 1 to 30 carbon atoms. Y is a saturated or unsaturated divalent organic group having 2 to 30 carbon atoms.

[0135] [ka] (In the formula, R 6a is an alkyl group having 1 to 4 carbon atoms. a is a saturated or unsaturated divalent hydrocarbon group having 4 to 10 carbon atoms, which may have an ether bond; and n represents the average number of repeating units and is 3 to 500.

[0136] <Pattern formation method> The present invention also provides a pattern formation method by a two-layer resist process using the above-mentioned composition for forming a resist underlayer film, which comprises forming a resist underlayer film on a substrate to be processed by the resist underlayer film formation method of the present invention, forming a resist upper layer film on the resist underlayer film by using a photoresist material, exposing the resist upper layer film to light and then developing it with a developer to form a pattern in the resist upper layer film, transferring the pattern to the resist underlayer film by dry etching using the resist upper layer film on which the pattern has been formed as a mask, and processing the substrate to be processed by using the resist underlayer film on which the pattern has been formed as a mask to form a pattern on the substrate to be processed.

[0137] The resist upper layer film in the two-layer resist process is preferably a photosensitive organometallic oxide film. The photosensitive organometallic oxide film exhibits resistance to etching by oxygen-based gas, so that in the two-layer resist process, the dry etching of the resist lower layer film using the resist upper layer film as a mask is preferably performed using an etching gas mainly containing oxygen-based gas.

[0138] In addition, the present invention provides a method for forming a pattern by a three-layer resist process using the above-mentioned composition for forming a resist underlayer film, which is a method for forming a pattern on a substrate to be processed, comprising the steps of: (I-1) forming a resist underlayer film on a substrate to be processed by the method for forming a resist underlayer film of the present invention; (I-2) forming a resist intermediate film on the resist underlayer film; (I-3) forming a resist upper layer film on the resist intermediate film using a photoresist material; (I-4) a step of forming a pattern on the resist upper layer film by pattern-exposing the resist upper layer film and then developing the resist upper layer film with a developer; (I-5) a step of transferring the pattern to the resist intermediate film by dry etching using the resist upper layer film on which the pattern has been formed as a mask; (I-6) a step of transferring a pattern to the resist underlayer film by dry etching using the resist intermediate film to which the pattern has been transferred as a mask; and (I-7) A step of processing the substrate to be processed using the resist underlayer film on which the pattern has been formed as a mask to form a pattern on the substrate to be processed. The present invention provides a pattern forming method comprising the steps of:

[0139] An example of a pattern forming method by a three-layer resist process will be described with reference to FIG. 1. First, as shown in FIG. 1(A), a resist underlayer film 3 is formed on a processable layer 2 of a processable substrate 1A including a support substrate 1 and a processable layer 2 formed thereon by the resist underlayer film forming method of the present invention, a resist intermediate film 4 (e.g., a silicon-containing resist intermediate film) is formed on the resist underlayer film 3 using a resist intermediate film material, and a resist upper layer film 5 is formed on the resist intermediate film 4 using a photoresist material. Subsequently, as shown in FIG. 1(B), an exposed portion 6 is formed in the resist upper layer film 5 by pattern exposure. Next, the exposed portion 6 is developed with a developer to form a resist upper layer film pattern 5a on the resist upper layer film 5 as shown in FIG. 1(C). Next, the resist upper layer film 5 on which the pattern 5a is formed is used as a mask to transfer the resist intermediate film pattern 4a to the resist intermediate film 4 by dry etching as shown in FIG. 1(D). Next, the resist underlayer film pattern 3a is transferred to the resist underlayer film 3 by dry etching using the resist intermediate film 4 to which the pattern 4a has been transferred as a mask, as shown in Fig. 1(E). Then, the processable layer 2 of the processable substrate 1A is processed using the resist underlayer film 3 to which the pattern 3a has been formed as a mask, to form a pattern 2a on the processable substrate 1 as shown in Fig. 1(F).

[0140] Since the silicon-containing resist intermediate film in the above three-layer resist process exhibits resistance to etching by oxygen-based gas, it is preferable that the dry etching of the resist underlayer film in the above three-layer resist process is performed using the silicon-containing resist intermediate film as a mask, using an etching gas mainly composed of oxygen-based gas.

[0141] As the silicon-containing resist intermediate film in the above three-layer resist process, a polysiloxane-based intermediate film is also preferably used. By imparting an anti-reflection effect to the silicon-containing resist intermediate film, reflection can be suppressed. In particular, for 193 nm exposure, if a material containing many aromatic groups and having high etching selectivity with the substrate is used as the organic film, the k value becomes high and the substrate reflection becomes high, but by imparting absorption to the silicon-containing resist intermediate film so that the k value becomes appropriate, it is possible to suppress reflection and make the substrate reflection 0.5% or less. As the silicon-containing resist intermediate film having an anti-reflection effect, anthracene is preferably used for 248 nm or 157 nm exposure, and polysiloxane with a pendant light-absorbing group having a phenyl group or a silicon-silicon bond and crosslinked by acid or heat is preferably used for 193 nm exposure.

[0142] In addition, the present invention provides a pattern formation method by a four-layer resist process using such a resist underlayer film forming composition, which comprises the steps of forming a resist underlayer film on a substrate to be processed by the resist underlayer film forming method of the present invention, forming a silicon-containing resist intermediate film on the resist underlayer film using a silicon-containing resist intermediate film material, forming an organic antireflective coating (BARC) or an adhesion film on the silicon-containing resist intermediate film, forming a resist upper layer film on the BARC or adhesion film using a photoresist material, exposing the resist upper layer film to light and then developing it with a developer to form a pattern on the resist upper layer film, transferring the pattern to the BARC or adhesion film and the silicon-containing resist intermediate film by dry etching using the resist upper layer film on which the pattern has been formed as a mask, transferring the pattern to the resist underlayer film by dry etching using the silicon-containing resist intermediate film on which the pattern has been transferred as a mask, and processing the substrate to be processed using the resist underlayer film on which the pattern has been formed as a mask to form a pattern on the substrate to be processed.

[0143] Alternatively, an inorganic hard mask may be formed instead of the silicon-containing resist intermediate film. In this case, at least a resist underlayer film is formed on a workpiece using the composition for forming a resist underlayer film of the present invention, an inorganic hard mask selected from a silicon oxide film, a silicon nitride film, and a silicon oxynitride film is formed on the resist underlayer film, a resist upperlayer film is formed on the inorganic hard mask using a photoresist composition, a circuit pattern is formed on the resist upperlayer film, the inorganic hard mask is etched using the resist upperlayer film on which the pattern has been formed as a mask, the resist underlayer film is etched using the inorganic hard mask on which the pattern has been formed as a mask, and the workpiece is etched using the resist underlayer film on which the pattern has been formed as a mask to form a pattern on the workpiece, thereby forming a semiconductor device circuit pattern on the substrate.

[0144] As described above, when an inorganic hard mask is formed on a resist underlayer film, a silicon oxide film, a silicon nitride film, and a silicon oxide nitride film (SiON film) can be formed by a CVD method, an ALD method, or the like. For example, methods for forming a silicon nitride film are described in JP-A-2002-334869 and WO-A-2004 / 066377. The thickness of the inorganic hard mask is preferably 5 to 200 nm, more preferably 10 to 100 nm. In addition, as the inorganic hard mask, a SiON film, which has a high effect as an anti-reflection film, is most preferably used. Since the substrate temperature during the formation of the SiON film is 300 to 500° C., the resist underlayer film needs to withstand a temperature of 300 to 500° C. The composition for forming the resist underlayer film used in the present invention has high heat resistance and can withstand high temperatures of 300 to 500° C., so that it is possible to combine an inorganic hard mask formed by a CVD method or an ALD method with a resist underlayer film formed by a spin coating method.

[0145] As described above, a photoresist film may be formed on the inorganic hard mask as a resist top layer, but an organic anti-reflective coating (BARC) or adhesion film may be formed on the inorganic hard mask by spin coating, and a photoresist film may be formed on top of that. In particular, when a SiON film is used as the inorganic hard mask, the two-layer anti-reflective coating of the SiON film and the BARC makes it possible to suppress reflection even in immersion exposure with a high NA exceeding 1.0. Another advantage of forming the BARC is that it has the effect of reducing the tailing of the photoresist pattern directly above the SiON film.

[0146] In the above pattern forming method, the resist upper layer film may be either positive or negative, and may be the same as a commonly used photoresist composition. The photoresist composition may contain metal atoms such as Sn, In, Ga, Ge, Al, Ce, La, Cs, Zr, Hf, Ti, Bi, Sb, and Zn. When forming the resist upper layer film using the above photoresist composition, it may be formed by spin coating or deposition processing using CVD or ALD.

[0147] When forming a photoresist composition by spin coating, the resist is prebaked after coating, preferably at 60 to 180° C. for 10 to 300 seconds. Thereafter, exposure is performed according to a conventional method, followed by post-exposure baking (PEB) and development to obtain a resist pattern. The thickness of the resist top layer is not particularly limited, but is preferably 10 to 500 nm, particularly preferably 20 to 400 nm.

[0148] When the photoresist composition is formed by deposition processing by CVD or ALD, the resist composition is an EUV photosensitive metal oxide film, and the metal is selected from Sn, Zr, Hf, Ti, Bi, Sb, etc., among which Sn, which has excellent EUV photosensitivity, is preferred. The metal oxide-containing film may be a photosensitive organometallic oxide film, such as an organotin oxide (e.g., haloalkyl Sn, alkoxyalkyl Sn, or amidoalkyl Sn). Some specific examples of suitable precursors include trimethyltin chloride, dimethyltin dichloride, methyltin trichloride, tris(dimethylamino)methyltin(IV), and (dimethylamino)trimethyltin(IV).

[0149] Metal oxide films may be deposited by PECVD or PEALD, for example using a Lam Vector® tool, with the Sn oxide precursor being separate from the O precursor / plasma in the ALD example. The deposition temperature is preferably in the range of 50° C. to 600° C. The deposition pressure is preferably between 100 and 6000 mTorr. The flow rate of the metal oxide-containing film precursor liquid (e.g., organotin oxide precursor) may be 0.01 to 10 cmm, and the gas flow rate (CO 2 , CO, Ar, N 2 ) may be 100-10000 sccm. Plasma power may be 200-1000 W per 300 mm wafer station using high frequency plasma (e.g., 13.56 MHz, 27.1 MHz, or higher). Deposition thickness is preferably 100-2000 Å.

[0150] Examples of the exposure light include high energy rays with a wavelength of 300 nm or less, specifically, excimer lasers with wavelengths of 248 nm, 193 nm, and 157 nm, soft X-rays with wavelengths of 3 to 20 nm, electron beams, and X-rays.

[0151] The method for forming the pattern on the resist upper layer film is preferably photolithography with a wavelength of 5 nm or more and 300 nm or less, direct drawing with an electron beam, nanoimprinting, or a combination of these.

[0152] In the pattern forming method, the development method is preferably alkaline development or development using an organic solvent.

[0153] Next, etching is performed using the obtained resist pattern as a mask. In the three-layer resist process, etching of the silicon-containing resist intermediate film and the inorganic hard mask is performed using a fluorocarbon-based gas as a mask for the upper resist pattern. This forms a silicon-containing resist intermediate film pattern and an inorganic hard mask pattern.

[0154] Next, the resist underlayer film is etched using the silicon-containing resist intermediate film pattern or the inorganic hard mask pattern as a mask. The etching of the resist underlayer film is preferably carried out using an etching gas mainly containing an oxygen-based gas.

[0155] The next etching of the workpiece can also be performed by a conventional method. For example, if the workpiece is SiO 2 For SiN or silica-based low dielectric constant insulating films, etching is mainly performed using fluorocarbon gases. When etching is performed using fluorocarbon gases for substrate processing, the silicon-containing resist intermediate film pattern in the three-layer resist process is peeled off at the same time as the substrate is processed.

[0156] The resist underlayer film obtained by the method for forming a resist underlayer film of the present invention is characterized by excellent etching resistance when etching the workpiece.

[0157] The workpiece (substrate) is not particularly limited, and may be Si, α-Si, p-Si, SiO 2 The substrate may be made of SiN, SiON, W, TiN, Al, or the like, or a substrate (support substrate) on which a layer to be processed is formed. 2Various low-k films and their stopper films such as SiON, SiN, p-Si, α-Si, W, W-Si, Al, Cu, and Al-Si are used, and can be formed to a thickness of usually 50 to 10,000 nm, particularly 100 to 5,000 nm. When forming a processed layer, the substrate and the processed layer are made of different materials.

[0158] The present invention also provides a method for forming a pattern on a workpiece substrate, comprising the steps of: (II-1) forming a resist underlayer film on a substrate having a step by the method for forming a resist underlayer film of the present invention; (II-2) forming a resist top layer film on the resist underlayer film; (II-3) a step of forming a pattern on the resist upper layer film by pattern-exposing the resist upper layer film and then developing the resist upper layer film with a developer; (II-4) a step of transferring the pattern to the resist underlayer film by dry etching using the resist upper layer film on which the pattern has been formed as a mask; (II-5) A step of processing the substrate to be processed using the resist underlayer film on which the pattern has been formed as a mask to form a pattern on the substrate to be processed. The present invention provides a pattern forming method comprising the steps of:

[0159] Between the resist underlayer film and the upper resist layer, an organic underlayer film, a silicon-containing film, an inorganic hard mask, an organic antireflective coating (BARC), an adhesion film, or the like may be laminated.

[0160] It is preferable to include a step of filling a substrate having a step with a resist underlayer film, transferring a fine pattern formed on an upper layer of the resist underlayer film (e.g., a pattern formed by a multi-patterning technique such as SADP or SAQP) to a hard mask directly on the resist underlayer film, transferring the hard mask pattern to the resist underlayer film, and transferring the resist underlayer film pattern to the substrate.

[0161] The materials, film thicknesses and formation methods of the organic underlayer film, silicon-containing film, inorganic hard mask, organic antireflective coating (BARC), adhesion film and substrate to be processed are the same as those described above.

[0162] The method for forming a resist underlayer film of the present invention is effective for the above-mentioned pattern formation method since it has excellent filling properties and planarization properties for a substrate to be processed having steps, and also has excellent etching resistance when the substrate to be processed is etched. EXAMPLES

[0163] The present invention will be described in more detail below with reference to Synthesis Examples, Examples, and Comparative Examples, but the present invention is not limited thereto. Note that, as for the molecular weight and dispersity, the weight average molecular weight (Mw) and number average molecular weight (Mn) in terms of polystyrene were determined by gel permeation chromatography (GPC) using tetrahydrofuran as an eluent, and the dispersity (Mw / Mn) was determined.

[0164] The following compounds (G1) to (G10) were used for synthesizing the polymers (A1) to (A11) and the comparative compounds (R1) to (R5).

[0165] [ka]

[0166] Synthesis Example (A) Polymer Synthesis

[0167] [Synthesis Example 1] Synthesis of polymer (A1) [ka] In a nitrogen atmosphere, 100.0 g of compound (G1), 14.7 g of 92% formaldehyde, 5.0 g of paratoluenesulfonic acid, and 200 g of ethylene glycol were added and stirred at an internal temperature of 140° C. for 8 hours. After cooling to room temperature, 500 g of methyl isobutyl ketone was added, and the organic layer was washed five times with 200 g of pure water, and then the organic layer was dried under reduced pressure. 300 g of THF was added to the residue, and the polymer was reprecipitated with 1200 g of hexane. The precipitated polymer was separated by filtration and dried under reduced pressure to obtain polymer (A1). The weight average molecular weight (Mw) and dispersity (Mw / Mn) were determined by GPC, and the results were as follows: (A1): Mw = 5,610, Mw / Mn = 3.60

[0168] [Synthesis Example 2] Synthesis of polymer (A2) [ka] In a nitrogen atmosphere, 180 g of compound (G2), 75 g of 37% formalin solution, and 5 g of oxalic acid were added and stirred at an internal temperature of 100° C. for 24 hours. After cooling to room temperature, 500 g of methyl isobutyl ketone was added, and the organic layer was washed five times with 200 g of pure water, and then the organic layer was dried under reduced pressure. 320 g of THF was added to the residue, and the polymer was reprecipitated with 1350 g of hexane. The precipitated polymer was separated by filtration and dried under reduced pressure to obtain polymer (A2). The weight average molecular weight (Mw) and dispersity (Mw / Mn) were determined by GPC, and the results were as follows: (A2): Mw = 11,200, Mw / Mn = 4.35

[0169] [Synthesis Example 3] Synthesis of polymer (A3) [ka] In a nitrogen atmosphere, 100.0 g of compound (G2), 48.3 g of compound (G3) and 450 g of 1,2-dichloroethane were mixed and uniformly dispersed at an internal temperature of 60°C, after which 82.4 g of methanesulfonic acid was added dropwise over 1 hour, and the mixture was heated and stirred at an internal temperature of 70°C for 24 hours. After cooling to room temperature, 1000 g of methyl isobutyl ketone was added, and the organic layer was washed five times with 200 g of pure water, and then the organic layer was dried under reduced pressure. 450 g of THF was added to the residue, and the polymer was reprecipitated with 1800 g of hexane. The precipitated polymer was separated by filtration and dried under reduced pressure to obtain polymer (A3). The weight average molecular weight (Mw) and dispersity (Mw / Mn) were determined by GPC, and the results were as follows: (A3): Mw=9,800, Mw / Mn=3.50

[0170] [Synthesis Example 4] Synthesis of polymer (A4) [ka] In a nitrogen atmosphere, 180.0 g of compound (G2), 58.0 g of compound (G4), 75.0 g of 37% formalin solution, 5.0 g of oxalic acid and 500 g of 2-methoxy-1-propanol were added and stirred at an internal temperature of 100°C for 24 hours. After cooling to room temperature, 1000 g of methyl isobutyl ketone was added, and the organic layer was washed five times with 200 g of pure water, and then the organic layer was dried under reduced pressure. 480 g of THF was added to the residue, and the polymer was reprecipitated with 2400 g of hexane. The precipitated polymer was separated by filtration and dried under reduced pressure to obtain polymer (A4). The weight average molecular weight (Mw) and dispersity (Mw / Mn) were determined by GPC, and the results were as follows: (A4): Mw = 9,350, Mw / Mn = 3.76

[0171] [Synthesis Example 5] Synthesis of polymer (A5) [ka] In a nitrogen atmosphere, 50.0 g of the compound (A2) obtained in Synthesis Example 2, 38.1 g of potassium carbonate, and 200 g of dimethylformamide were added to prepare a uniform dispersion at 50°C, and then 23.4 g of allyl bromide was slowly added dropwise and stirred at an internal temperature of 50°C for 8 hours. The mixture was cooled to room temperature, and 400 ml of methyl isobutyl ketone and 300 g of pure water were added to the reaction solution to dissolve the precipitated salt, and the separated aqueous layer was removed. The organic layer was further washed six times with 100 g of a 3% aqueous nitric acid solution and 100 g of pure water, and then the organic layer was dried under reduced pressure to obtain a polymer (A5). The weight average molecular weight (Mw) and dispersity (Mw / Mn) were determined by GPC, and the results were as follows: (A5): Mw=12,200, Mw / Mn=4.38

[0172] [Synthesis Example 6] Synthesis of polymer (A6) [ka] In a nitrogen atmosphere, 50.0 g of the compound (A2) obtained in Synthesis Example 2, 41.9 g of potassium carbonate, and 200 g of dimethylformamide were added to prepare a uniform dispersion at 50°C, and then 29.5 g of 3-bromo-1-propyne was slowly added dropwise and stirred at an internal temperature of 50°C for 8 hours. The reaction solution was cooled to room temperature, and 400 ml of methyl isobutyl ketone and 300 g of pure water were added to dissolve the precipitated salt, and the separated water layer was removed. The organic layer was further washed six times with 100 g of 3% aqueous nitric acid solution and 100 g of pure water, and the organic layer was dried under reduced pressure to obtain polymer (A6). The weight average molecular weight (Mw) and dispersity (Mw / Mn) were determined by GPC, and the results were as follows: (A6): Mw=12,800, Mw / Mn=4.43

[0173] [Synthesis Example 7] Synthesis of polymer (A7) [ka] In a nitrogen atmosphere, 100.0 g of compound (G5), 24.3 g of 37% formalin solution, and 300 g of 2-methoxy-1-propanol were added, and the mixture was made into a homogeneous solution at an internal temperature of 80° C., after which 25.0 g of a 20% solution of paratoluenesulfonic acid in 2-methoxy-1-propanol was slowly added, and the mixture was stirred at an internal temperature of 110° C. for 8 hours. After cooling to room temperature, 500 g of methyl isobutyl ketone was added, and the organic layer was washed five times with 200 g of pure water, and then the organic layer was dried under reduced pressure. 300 g of THF was added to the residue, and the polymer was reprecipitated with 1500 g of methanol. The precipitated polymer was separated by filtration and dried under reduced pressure to obtain polymer (A7). The weight average molecular weight (Mw) and dispersity (Mw / Mn) were determined by GPC, and the results were as follows: (A7): Mw=5,340, Mw / Mn=2.40

[0174] [Synthesis Example 8] Synthesis of polymer (A8) [ka] In a nitrogen atmosphere, 90.1 g of compound (G6), 25.2 g of 37% formalin solution, and 270 g of 2-methoxy-1-propanol were added, and the mixture was made into a homogeneous solution at an internal temperature of 80° C., and then 18 g of a 20% solution of paratoluenesulfonic acid in 2-methoxy-1-propanol was slowly added, and the mixture was stirred at an internal temperature of 110° C. for 8 hours. After cooling to room temperature, 600 g of methyl isobutyl ketone was added, and the organic layer was washed five times with 200 g of pure water, and then the organic layer was dried under reduced pressure. 320 g of THF was added to the residue, and the polymer was reprecipitated with 1350 g of methanol. The precipitated polymer was separated by filtration and dried under reduced pressure to obtain polymer (A8). The weight average molecular weight (Mw) and dispersity (Mw / Mn) were determined by GPC, and the results were as follows: (A8): Mw=3,520, Mw / Mn=2.60

[0175] [Synthesis Example 9] Synthesis of polymer (A9) [ka] In a nitrogen atmosphere, 100.0 g of compound (G6), 24.5 g of compound (G7) and 450 g of 1,2-dichloroethane were mixed and uniformly dispersed at an internal temperature of 60°C, after which 64.1 g of methanesulfonic acid was added dropwise over 1 hour, and the mixture was heated and stirred at an internal temperature of 70°C for 24 hours. After cooling to room temperature, 1000 g of methyl isobutyl ketone was added, and the organic layer was washed five times with 200 g of pure water, and then the organic layer was dried under reduced pressure. 450 g of THF was added to the residue, and the polymer was reprecipitated with 1300 g of methanol. The precipitated polymer was separated by filtration and dried under reduced pressure to obtain polymer (A9). The weight average molecular weight (Mw) and dispersity (Mw / Mn) were determined by GPC, and the results were as follows: (A9): Mw=5,300, Mw / Mn=3.30

[0176] [Synthesis Example 10] Synthesis of polymer (A10) [ka] In a nitrogen atmosphere, 50.0 g of compound (G6), 17.8 g of compound (G8), 3.0 g of paratoluenesulfonic acid, and 205 g of 2-methoxy-1-propanol were added, and the mixture was made into a homogeneous solution at an internal temperature of 100°C. Then, 17.1 g of 37% aqueous formalin solution was slowly added dropwise, and the mixture was stirred at an internal temperature of 110°C for 8 hours. After cooling to room temperature, 500 g of methyl isobutyl ketone was added, and the organic layer was washed five times with 100 g of pure water, and then the organic layer was dried under reduced pressure. 210 g of THF was added to the residue, and the polymer was reprecipitated with 1260 g of hexane. The precipitated polymer was separated by filtration and dried under reduced pressure to obtain polymer (A10). The weight average molecular weight (Mw) and dispersity (Mw / Mn) were determined by GPC, and the results were as follows: (A10): Mw = 6,400, Mw / Mn = 3.70

[0177] [Synthesis Example 11] Synthesis of polymer (A11) [ka] In a nitrogen atmosphere, 50.0 g of the compound (A8) obtained in Synthesis Example 8, 29.9 g of potassium carbonate, and 200 g of dimethylformamide were added to prepare a uniform dispersion at 50°C, and then 18.0 g of 3-bromo-1-propyne was slowly added dropwise and stirred at an internal temperature of 50°C for 8 hours. The mixture was cooled to room temperature, and 300 ml of methyl isobutyl ketone and 200 g of pure water were added to the reaction solution to dissolve the precipitated salt, and the separated water layer was removed. The organic layer was further washed six times with 100 g of a 3% aqueous nitric acid solution and 100 g of pure water, and the organic layer was dried under reduced pressure to obtain a polymer (A11). The weight average molecular weight (Mw) and dispersity (Mw / Mn) were determined by GPC, and the results were as follows: (A11): Mw = 4,400, Mw / Mn = 4.10

[0178] [Synthesis Example 12] Synthesis of Comparative Compound (R1) [ka] Under a nitrogen atmosphere, 160.2 g of 1,5-dihydroxynaphthalene, 64.9 g of a 37% formaldehyde solution, and 300 g of 2-methoxy-1-propanol were added and homogenized at an internal temperature of 100 ° C. Then, 18.0 g of a 20% 2-methoxy-1-propanol solution of paratoluenesulfonic acid, which had been mixed and homogenized in advance, was slowly added, and the reaction was carried out at an internal temperature of 80 ° C. for 8 hours. After the reaction was completed, the mixture was cooled to room temperature, 1000 ml of methyl isobutyl ketone was added, and the mixture was washed six times with 200 ml of pure water, and the organic layer was dried under reduced pressure. 300 g of THF was added to the residue to make a homogenous solution, and then crystallized in 2000 g of hexane. The precipitated crystals were separated by filtration, washed twice with 500 g of hexane, and collected. The collected crystals were dried in a vacuum at 70 ° C. to obtain a polymer (R1). The weight average molecular weight (Mw) and dispersity (Mw / Mn) were determined by GPC, and the results were as follows: (R1): Mw = 4,000, Mw / Mn = 3.02

[0179] [Synthesis Example 13] Synthesis of Comparative Compound (R2) [ka] Under a nitrogen atmosphere, 42.8 g of compound (G6), 15.7 g of potassium carbonate, and 150 g of DMF were added to obtain a uniform dispersion at an internal temperature of 50°C. 28.2 g of 3-bromo-1-propyne was slowly added, and the reaction was carried out at an internal temperature of 50°C for 24 hours. 300 ml of methyl isobutyl ketone and 300 g of pure water were added to the reaction solution to dissolve the precipitated salt, and then the separated aqueous layer was removed. The organic layer was further washed six times with 100 g of 3% aqueous nitric acid solution and 100 g of pure water, and the organic layer was dried under reduced pressure to obtain compound (R2). The weight average molecular weight (Mw) and dispersity (Mw / Mn) were determined by GPC, and the results were as follows: (R2): Mw=560, Mw / Mn=1.01

[0180] [Synthesis Example 14] Synthesis of Comparative Compound (R3) [ka] In a nitrogen atmosphere, 41.2 g of compound (G9) and 160 g of methylene chloride were mixed. 19.2 g of methanesulfonic acid was slowly added dropwise, and the reaction was carried out under heating and reflux for 8 hours. After cooling to room temperature, 250 g of toluene was added, and the organic layer was washed five times with 100 g of pure water. The organic layer was dried under reduced pressure to obtain compound (R3). The weight average molecular weight (Mw) and dispersity (Mw / Mn) were determined by GPC, and the results were as follows: (R3): Mw=1850, Mw / Mn=1.26

[0181] [Synthesis Example 15] Synthesis of Comparative Compound (R4) [ka] Under a nitrogen atmosphere, 230.0 g of compound (G2), 20.0 g of compound (G10) and 1040 g of dichloromethane were added to obtain a homogeneous solution at an internal temperature of 35°C, and then 9.0 g of trifluoromethanesulfonic acid and 0.6 g of 3-mercaptopropionic acid dissolved in 20.0 g of dichloromethane were added, and the reaction was carried out under heating and reflux for 4 hours. After cooling to room temperature, the organic layer was washed five times with 300 g of pure water. The organic layer was dried under reduced pressure to obtain compound (R4). The weight average molecular weight (Mw) and dispersity (Mw / Mn) were determined by GPC, and the results were as follows: (R4): Mw = 680, Mw / Mn = 1.26

[0182] [Synthesis Example 16] Synthesis of Comparative Compound (R5) [ka] Under a nitrogen atmosphere, 20.0 g of the comparative compound (R4) obtained in Synthesis Example 15, 32.0 g of potassium carbonate, and 62.0 g of acetone were added to form a homogeneous solution at 56°C, and then 28.0 g of 3-bromo-1-propyne was slowly added to the reactor and stirred at 56°C for 3 hours. The mixture was cooled to room temperature, and excess potassium carbonate and salts were removed by filtration, and the precipitate was washed with acetone. The organic layer was washed five times with 300 g of pure water. The organic layer was dried under reduced pressure to obtain compound (R5). The weight average molecular weight (Mw) and dispersity (Mw / Mn) were determined by GPC, and the results were as follows: (R5): Mw = 1,040, Mw / Mn = 1.38

[0183] [Synthesis Example (C) Synthesis of Crosslinking Agent]

[0184] [Synthesis Example 17] Synthesis of compound (C1) [ka] In a nitrogen atmosphere, 219.0 g of bis(4-bromophenyl) ether and 750 g of t-butyl methyl ether were cooled to an internal temperature of -20°C, and 500 mL of 2.67 M n-butyl lithium hexane solution was added and stirred at an internal temperature of -20°C for 20 minutes. 229.0 g of 9-fluorenone was added, and the temperature was gradually raised to room temperature and stirred at room temperature for 4 hours. After adding 500 g of pure water to stop the reaction, the separated aqueous layer was removed. The organic layer was further washed five times with 300 g of pure water, concentrated under reduced pressure, and 1000 g of hexane was added to precipitate crystals. The precipitated crystals were separated by filtration, washed twice with 500 g of hexane, collected, and then dried under reduced pressure to obtain compound (C1). (C1): Mw=540, Mw / Mn=1.02

[0185] [Composition for forming resist underlayer film (UDL-1)] The polymer (A1) for forming a resist underlayer film was dissolved in propylene glycol monomethyl ether acetate (PGMEA) containing 0.5 mass % of a surfactant FC-4430 (manufactured by Sumitomo 3M Limited) in the ratio shown in Table 2, and the resultant was filtered through a 0.02 μm membrane filter to prepare a composition for forming a resist underlayer film (UDL-1).

[0186] [Preparation of compositions for forming resist underlayer films (UDL-2 to 15) and comparative compositions for forming resist underlayer films (Comparative UDL-1 to 5)] Each chemical solution was prepared in the same manner as UDL-1, except that the type and content of each component were as shown in Table 2. In Table 2, "-" indicates that the corresponding component was not used. The crosslinking agent used was the compound (C1) synthesized in Synthesis Example 17 above and the compound represented by the following formula (C2), the acid generator (TAG) used was the compound represented by the following formula (E1), the high boiling point solvent used was the compound represented by the following formula (B1), and the blending polymer used was the compound represented by the following formula (BP1).

[0187] [Crosslinking agent] The crosslinking agents used in the composition for forming the resist underlayer film are shown below. [ka]

[0188] [Acid generator] The thermal acid generator (E1) used in the composition for forming the resist underlayer film is shown below. [ka]

[0189] [High boiling point solvent] Table 1 shows the high boiling point solvent (B1) used in the composition for forming the resist underlayer film.

[0190] [Table 1]

[0191] [Blend polymers] The blending polymer (BP1) used in the composition for forming the resist underlayer film is shown below. [ka] (BP1): Mw = 9,300, Mw / Mn = 3.30

[0192] [Table 2]

[0193] [Example 1: Film thickness evaluation] The resist underlayer film forming compositions (UDL-1 to 15, Comparative Examples UDL-1 to 5) prepared above were applied onto silicon substrates and baked at 250°C for 60 seconds. The film thickness from the center to the outer periphery of the substrate was then measured to calculate the average film thickness (a [nm]).

[0194] Separately from the above, substrates were prepared by heating at 250°C for 60 seconds, and the plasma treatment conditions described below were carried out to form resist underlayer films. The film thickness from the center to the outer periphery of the substrate was measured to calculate the average film thickness (b [nm]).

[0195] The change in the thickness of the resist underlayer film due to plasma exposure and the thickness uniformity after plasma exposure were evaluated. For thickness uniformity, the thickness of a 300 mm wafer was measured from the center to the outer periphery at 225 points, and a difference between the maximum and minimum thicknesses of the measured values ​​was rated as "very good" if it was less than 3% of the average thickness (b), "good" if it was 3% to 5%, and "poor" if it was 5% or more.

[0196] Additional processing conditions (plasma processing) Each substrate was heated at 250° C. for 60 seconds and then subjected to plasma treatment under the following conditions using a Telius etching device manufactured by Tokyo Electron. Plasma treatment conditions Chamber pressure: 100mT RF Power (Top): 100W RF power (bottom): 3500W H 2 Gas flow rate: 200sccm Time: 20sec

[0197] The results are shown in Table 3.

[0198] [Table 3] * Film thickness uniformity A: Very good B: Good C: Poor

[0199] As shown in Table 3, in the resist underlayer film forming method of the present invention (Examples 1-1 to 1-15), good results were obtained in terms of film thickness uniformity after plasma irradiation. The polymer contained in the resist underlayer film forming composition used in the present invention has a structure containing a high carbon density fluorene skeleton, which is repeatedly bonded via a methylene group, and therefore has a characteristic that dissociation and recombination of carbon bonds is easily promoted by plasma irradiation. However, since it is a high molecular weight substance containing a crosslinking group structure containing an oxygen atom and a methylene group, it is presumed that the curability, density, and heat resistance of the resist underlayer film are improved, the scattering of solid components in the film due to plasma irradiation can be mitigated, and a resist underlayer film showing a small change in film thickness before and after plasma irradiation and good film thickness uniformity was formed. In particular, the film thickness uniformity of Examples 1-1, 1-2, 1-5, 1-6, 1-7, 1-8, and 1-11, which used a resist underlayer film forming composition containing a polymer in which k in the above formula (1) is 0, was good. When k in the above formula (1) is 1, the fluidity of the polymer can be improved, which is effective in improving the planarization characteristics. However, from the viewpoint of curability, it is presumed that k is preferably 0.

[0200] On the other hand, in Comparative Example 1-1, the film thickness change before and after plasma irradiation was large compared to the examples. In Comparative Examples 1-2 to 1-5, the film thickness difference before and after plasma irradiation was large, and the film thickness uniformity of the resist underlayer film after plasma irradiation was insufficient. In these Comparative Examples, an oligomer or compound not containing a methylene group was used, so the hardening of the resist underlayer film before the additional treatment was insufficient, and not only the dissociation and recombination of carbon bonds progressed, but also the scattering of solid components in the film actively occurred. For this reason, it is presumed that the film thickness change before and after plasma irradiation was large, and the film thickness uniformity after plasma irradiation was insufficient.

[0201] [Example 2: Etching resistance evaluation] The resist underlayer film forming compositions (UDL-1 to 15, Comparative Examples UDL-1 to 5) prepared above were applied onto a silicon substrate and baked at 250°C for 60 seconds, after which the film thickness from the center to the outer periphery of the substrate was measured and the average film thickness (c [nm]) was calculated. Next, CF4 Etching was performed using gas, and the film thickness d was measured. CF 4 The thickness of the film etched in one minute was calculated as the etching rate A (nm / min) from the thickness of the film etched using the gas during the specified time (thickness of film c - thickness of film d). The results are shown in Table 4.

[0202] Separately from the above, a substrate was prepared by heating at 250° C. for 60 seconds, and the following plasma treatment conditions were carried out to form a resist underlayer film, and the film thickness e was measured. Next, a CF 4 Etching was performed using gas, and the film thickness f was measured. CF 4 The etching rate B (nm / min) was calculated from the thickness of the film etched in one minute using the gas during a specified time (thickness e - thickness f). The smaller the etching rate, the higher the CF 4 This means that the etching resistance against gas is excellent.

[0203] The etching resistance of the film that had been subjected to the additional treatment was compared with that of the film that had been fired at 250° C., and the improvement in etching resistance due to the additional treatment (etching rate A (nm / min)−etching rate B (nm / min)) was calculated.

[0204] The etching conditions are as follows. CF 4 Gas dry etching conditions Chamber pressure: 100mT RF power (top): 500W RF power (bottom): 400W CF 4 Gas flow rate: 300sccm Time: 30sec

[0205] The additional treatment conditions (plasma irradiation) were the same as those in Example 1.

[0206] [Table 4]

[0207] As shown in Table 4, in the resist underlayer film forming method of the present invention (Examples 1-1 to 1-15), CF 4 The results showed that the dry etching resistance against gases was greatly improved. The polymer contained in the composition for forming the resist underlayer film used in the present invention is a high molecular weight substance containing a high carbon density fluorene skeleton in the repeating unit, so that the carbon bonds of the resist underlayer film are easily dissociated and recombined by plasma irradiation to reconstruct it into a cured film having a diamond-like carbon structure, which is believed to be the reason for the excellent dry etching resistance. In particular, when k in the above formula (1) is 0 and Ar 1 and Ar 2 The dry etching resistance of Examples 2-2, 2-5, 2-6, 2-8 and 2-11, which use a polymer in which n in the above formula (1A) is benzene, is good. 1 is 0 and R 2 Example 2-2, which used a polymer in which the carbon atom is a hydrogen atom, showed extremely good results. It is presumed that the polymer (A2) used in Example 2-2 has a large proportion of fluorene skeletons in the repeating unit, so that the dissociation and recombination of carbon bonds in the resist underlayer film is easily promoted by plasma exposure, and furthermore, the proportion of crosslinking groups (hydroxyl groups and methylene) in the repeating unit is also large, so that the denseness of the resist underlayer film is further improved by plasma exposure, and good dry etching resistance is shown.

[0208] In Comparative Example 2-1, the repeating unit of the polymer does not contain a fluorene skeleton, so it is presumed that the modification of the resist underlayer film by plasma irradiation was insufficient. In Comparative Example 2-2, the polymer contains a fluorene skeleton, but is a compound rather than a polymer, so that the curability of the resist underlayer film before plasma irradiation is insufficient, and solid components in the resist underlayer film fly off at the same time as the carbon bonds are dissociated and recombined by plasma irradiation, so that the film modification by plasma irradiation does not proceed sufficiently. In Comparative Example 2-3, the polymer contains a fluorene skeleton, but has a structure that does not contain a methylene group, and has a small molecular weight, so that the curability of the resist underlayer film before plasma irradiation is insufficient, and solid components in the resist underlayer film fly off at the same time as the carbon bonds are dissociated and recombined by plasma irradiation, so that the film modification by plasma irradiation does not proceed sufficiently. Comparative Examples 2-4 and 2-5 contain a fluorene skeleton but do not contain a methylene group, and are oligomers. Therefore, it is presumed that the hardening of the resist underlayer film before plasma exposure was insufficient, and that the solid components in the resist underlayer film were scattered simultaneously with the dissociation and recombination of carbon bonds due to plasma exposure, and the film modification by plasma exposure did not proceed sufficiently.

[0209] From the above results, it can be said that in order to achieve both high-level modification of the resist underlayer film by plasma exposure and high-level film thickness uniformity, the structure of the fluorene skeleton and the methylene group is important, and it is preferable for the structure containing the fluorene skeleton to be a polymer linked via a methylene group.

[0210] [Example 3: Flatness evaluation] The resist underlayer film-forming compositions (UDL-1 to 15 and Comparative Examples UDL-1 to 5) were each applied to a SiO 2 A resist underlayer film having a thickness of 100 nm was formed by coating the resist on a wafer substrate and baking the resist at 250° C. for 60 seconds, followed by a plasma irradiation treatment similar to that used in the dry etching resistance evaluation.

[0211] The substrate used was a base substrate 7 (SiO 2 The pattern is filled with a resist underlayer film 8 as shown in FIG. 2(I). Next, a plasma irradiation process is performed, and the cross-sectional shape of each obtained wafer substrate is observed using an electron microscope (S-4700) manufactured by Hitachi, Ltd., and the step Delta 10 of the resist underlayer film (filling film) 10 in the line pattern dense part and the non-line pattern formed part in the base substrate 9 is evaluated as shown in FIG. 3(T) and (U). In this evaluation, the smaller the step, the better the planarization characteristics. The results are shown in Table 5.

[0212] [Table 5]

[0213] As shown in Table 5, it was confirmed that the resist underlayer film-forming compositions (UDL-1 to 15) of the present invention can provide resist underlayer films with excellent planarization properties even after plasma exposure. On the other hand, it was confirmed that Comparative Examples 3-1 to 3-5, which used Comparative Examples UDL-1 to 5, which were confirmed to have a large change in film thickness before and after plasma exposure in Example 1, had insufficient planarization properties.

[0214] [Example 4: Pattern formation method] The resist underlayer film-forming compositions (UDL-1 to 15 and Comparative Examples UDL-1 to 5) were each applied to a SiO 2 The coating was applied onto a silicon wafer substrate on which a film had been formed, and baked in air at 250° C. for 60 seconds to form a 100 nm thick underlayer precursor film, which was then subjected to the same plasma irradiation treatment as in the dry etching resistance evaluation.

[0215] In Comparative Example 4-6, UDL-1 was replaced with SiO 2The resist underlayer film was formed in a thickness of 100 nm by applying the solution onto a silicon wafer substrate on which a film had been formed and baking the solution in air at 250° C. for 60 seconds. This resist underlayer film was not irradiated with plasma.

[0216] A silicon-containing resist intermediate layer material (SOG-1) was applied onto the resist underlayer film prepared by the above method and baked at 220°C for 60 seconds to form a resist intermediate layer film with a thickness of 20 nm, and a single layer resist for ArF of the resist upper layer film material was applied onto that and baked at 105°C for 60 seconds to form a photoresist film with a thickness of 100 nm. An immersion protective film material (TC-1) was applied onto the photoresist film and baked at 90°C for 60 seconds to form a protective film with a thickness of 50 nm.

[0217] The silicon-containing resist intermediate layer material (SOG-1) was prepared by dissolving a polymer represented by ArF silicon-containing intermediate film polymer (SiP1) and a crosslinking catalyst (CAT1) in an organic solvent containing 0.1 mass % of FC-4430 (manufactured by Sumitomo 3M) in the ratios shown in Table 6, and filtering the solution through a fluorine resin filter having a pore size of 0.1 μm.

[0218] [Table 6]

[0219] The structural formulae of the ArF silicon-containing intermediate film polymer (SiP1) and crosslinking catalyst (CAT1) used are shown below.

[0220] [ka]

[0221] The resist top layer film material (ArF single layer resist) was prepared by dissolving a polymer (RP1), an acid generator (PAG1), and a basic compound (Amine1) in a solvent containing 0.1 mass % of a surfactant FC-4430 (Sumitomo 3M Limited) in the ratios shown in Table 7, and filtering the solution through a 0.1 μm fluororesin filter.

[0222] [Table 7]

[0223] The polymer (RP1), acid generator (PAG1), and basic compound (Amine1) used in the resist top layer material (ArF single layer resist) are shown below.

[0224] [ka]

[0225] The immersion protective film material (TC-1) was prepared by dissolving the protective film polymer (PP1) in an organic solvent in the ratio shown in Table 8, and filtering through a 0.1 μm fluorine resin filter.

[0226] [Table 8]

[0227] The polymer (PP1) used in the immersion protective film material (TC-1) is shown below.

[0228] [ka]

[0229] Next, the resist was exposed using an ArF immersion exposure apparatus (Nikon Corporation; NSR-S610C, NA 1.30, σ 0.98 / 0.78, 35 degree dipole s-polarized illumination, 6% halftone phase shift mask), baked at 100°C for 60 seconds (PEB), and developed in a 2.38 mass% tetramethylammonium hydroxide (TMAH) aqueous solution for 30 seconds to obtain a 40 nm 1:1 positive line and space pattern (resist pattern).

[0230] Next, the silicon-containing resist intermediate layer material (SOG-1) is etched by dry etching using the resist pattern as a mask using a Tokyo Electron etching device Telius to form a hard mask pattern, the resist underlayer film is etched using the obtained SOG-1 pattern as a mask to form a resist underlayer film pattern, and the obtained resist underlayer film pattern is used as a mask to form a SiO 2 The film was etched under the following etching conditions.

[0231] Transfer conditions of resist pattern to silicon-containing resist intermediate layer material (SOG-1). Chamber pressure: 50mT RF power (top): 500W RF power (bottom): 300W CF 4 Gas flow rate: 150sccm CHF 3 Gas flow rate: 50sccm Time: 15sec

[0232] Conditions for transferring the silicon atom-containing resist intermediate layer material (SOG-1) pattern to the resist underlayer film. Chamber pressure: 10mT RF power (top): 1,000W RF power (bottom): 300W CO 2 Gas flow rate: 320sccm N 2 Gas flow rate: 80sccm Time: 55sec

[0233] SiO of resist underlayer film pattern 2 Membrane transfer conditions. Chamber pressure: 100mT RF power (top): 500W RF power (bottom): 300W CF 4 Gas flow rate: 150sccm CHF 3 Gas flow rate: 30sccm O 2 Gas flow rate: 10sccm Time: 130sec

[0234] The cross section of the pattern was observed using an electron microscope (S-4700) manufactured by Hitachi, Ltd. The results are shown in Table 9.

[0235] [Table 9]

[0236] As shown in Table 9, in Examples 4-1 to 4-15 using the resist underlayer film forming composition (UDL-1 to 15) of the present invention, the resist upper layer film pattern was successfully transferred to the substrate to be processed in all cases, and it was confirmed that the resist underlayer film forming method of the present invention is suitably used for fine processing by the multilayer resist method. On the other hand, in Comparative Examples 4-2 to 4-5 using Comparative Examples UDL-2 to 5, which were confirmed to have insufficient etching resistance compared to the resist underlayer film forming method of the present invention in the above etching resistance evaluation, it was observed that the pattern shape after substrate transfer etching was distorted. In addition, in Comparative Example 4-1 using Comparative Example UDL-1, which had extremely insufficient etching resistance, and Comparative Example 4-6, which did not undergo plasma irradiation, no pattern remained, and it was observed that the pattern was not transferred to the substrate to be processed due to insufficient etching resistance of the resist underlayer film.

[0237] From the above, the resist underlayer film forming method of the present invention can form a resist underlayer film with excellent film thickness uniformity that exhibits excellent dry etching resistance during substrate processing by plasma irradiation, and is therefore extremely useful for next-generation microfabrication processes. In addition, it has become clear that the pattern forming method of the present invention using this method can form a fine pattern with high accuracy even if the substrate to be processed has steps.

[0238] This specification includes the following inventions.

[0239] [1]: A method for forming a resist underlayer film on a substrate, comprising the steps of: (i) coating a resist underlayer film-forming composition, the composition including (A) a polymer and (B) an organic solvent, onto the substrate, and curing the composition by heat treatment at a temperature of 100°C or higher and 800°C or lower for 10 to 7,200 seconds to form an underlayer film precursor film; and (ii) irradiating the substrate on which the underlayer film precursor film has been formed with plasma to form a resist underlayer film, wherein the (A) polymer includes a constitutional unit represented by the following general formula (1) and has a weight average molecular weight of 2,500 to 20,000 in terms of polystyrene, as determined by gel permeation chromatography. [ka] (In the formula, Ar 1 and Ar 2 are independently a substituted or unsubstituted benzene ring or a substituted or unsubstituted naphthalene ring, X is a structure represented by the following general formula (1A), Y is a divalent organic group having 6 to 50 carbon atoms, and k is 0 or 1. [ka] (In the formula, n 1 is 0 or 1, n 2 is 1 or 2, R 2 R is a hydrogen atom, an organic group having 1 to 10 carbon atoms, or a structure represented by the following general formula (1B). 3is a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, or a group represented by the following general formula (1C), 3 is 0, 1, or 2, * is the bond to the methylene group, and ** is the bond to the quaternary carbon of the fluorene.) [ka] (wherein * represents the bond site to the oxygen atom, R A is a divalent organic group having 1 to 10 carbon atoms, R B is a hydrogen atom or a monovalent organic group having 1 to 10 carbon atoms. [ka] (In the formula, R 4 is a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms, and the hydrogen atom on the benzene ring in the formula may be substituted with a methyl group or a methoxy group.

[0240] [2]: The method for forming a resist underlayer film according to the above [1], wherein in the above general formula (1), Y is any of the structures represented by the following formula (Y-1): [ka] (The hydrogen atoms in the above structure may be substituted with hydroxyl groups or monovalent organic groups having 1 to 10 carbon atoms.)

[0241] [3]: In the general formula (1A), R 2 The method for forming a resist underlayer film according to the above [1] or [2], wherein

[0242] [4]: In the general formula (1A), R 2 is a hydrogen atom or a structure represented by the general formula (1B), 2The method for forming a resist underlayer film according to any one of the above [1] to [3], wherein, in the structure constituting the above, a ratio of hydrogen atoms is a and a ratio of the structure represented by the general formula (1B) is b, the relationship of a+b=1, 0.1≦b≦0.9 is satisfied.

[0243] [5]: In the general formula (1), Ar 1 and Ar 2 is an unsubstituted benzene ring, and in general formula (1A), n1 is 0, n2 is 1 or 2, and n3 is 0.

[0244] [6]: The method for forming a resist underlayer film according to any one of the above [1] to [5], wherein in the general formula (1), k is 0.

[0245] [7]: The method for forming a resist underlayer film according to any one of the above [1] to [6], wherein the weight average molecular weight of the polymer (A) in terms of polystyrene as determined by a gel permeation chromatography method is from 7,000 to 15,000.

[0246] [8]: The method for forming a resist underlayer film according to any one of the above [1] to [7], wherein the composition for forming a resist underlayer film further contains one or more of (C) a crosslinking agent, (D) a surfactant, (E) an acid generator, and (F) a plasticizer.

[0247] [9]: The method for forming a resist underlayer film according to any one of the above [1] to [8], characterized in that the (B) organic solvent is a mixture of one or more organic solvents having a boiling point of less than 180°C and one or more (B-1) high-boiling point solvents which are organic solvents having a boiling point of 180°C or higher.

[0248]

[10] In the step (ii), the plasma irradiation is performed by N 2 , N.F. 3 , H 2The method for forming a resist underlayer film according to any one of the above [1] to [9], characterized in that the method is carried out in an atmosphere of a fluorocarbon, a rare gas, or a mixture of any of these.

[0249]

[11] : The method for forming a resist underlayer film according to any one of the above [1] to

[10] , wherein in the step (i), the heat treatment is carried out in an atmosphere having an oxygen concentration of 1% or more and 21% or less.

[0250]

[12] : The method for forming a resist underlayer film according to any one of the above [1] to

[10] , wherein in the step (i), the heat treatment is carried out in an atmosphere having an oxygen concentration of less than 1%.

[0251]

[13] : A method for forming a pattern on a substrate to be processed, comprising: (I-1) forming a resist underlayer film on the substrate to be processed by the method for forming a resist underlayer film according to any one of the above [1] to

[12] ; (I-2) forming a resist intermediate film on the resist underlayer film; (I-3) forming a resist upper layer film on the resist intermediate film using a photoresist material; (I-4) pattern-exposing the resist upper layer film and then developing it with a developer to form a pattern on the resist upper layer film; (I-5) transferring a pattern to the resist intermediate film by dry etching using the resist upper layer film on which the pattern has been formed as a mask; (I-6) transferring a pattern to the resist underlayer film by dry etching using the resist intermediate film on which the pattern has been transferred as a mask; and (I-7) processing the substrate to be processed by using the resist underlayer film on which the pattern has been formed as a mask to form a pattern on the substrate to be processed.

[0252]

[14] : A method for forming a pattern on a processed substrate, comprising: (II-1) forming a resist underlayer film on a processed substrate having a step by the resist underlayer film forming method according to any one of the above [1] to

[12] ; (II-2) forming a resist upper layer film on the upper layer of the resist underlayer film; (II-3) exposing the resist upper layer film to a pattern and developing it with a developer to form a pattern on the resist upper layer film; (II-4) using the resist upper layer film on which the pattern has been formed as a mask, transferring the pattern to the resist underlayer film by dry etching; and (II-5) processing the processed substrate by using the resist underlayer film on which the pattern has been formed as a mask to form a pattern on the processed substrate.

[0253]

[15] : The pattern formation method according to the above

[13] or

[14] , wherein the aspect ratio of the step of the substrate to be processed is 3 or more.

[0254] The present invention is not limited to the above-described embodiment. The above-described embodiment is merely an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included in the technical scope of the present invention. [Explanation of symbols]

[0255] 1... Support substrate, 1A... Processed substrate 2... Processed layer, 2a... pattern (pattern formed on a processing layer), 3... resist underlayer film, 3a...resist underlayer film pattern, 4...resist intermediate film, 4a...resist intermediate film pattern, 5...resist upper layer film, 5a: resist upper layer film pattern; 6: exposed portion; 7...Base substrate having dense lines and spaces; 8...Resist underlayer film; 9... Base substrate having dense lines and spaces; 10... Resist underlayer film; Delta10: Step difference between the patterned portion and the non-patterned portion of the resist underlayer film 10.

Claims

1. A method for forming a resist underlayer film on a substrate, comprising the steps of: (i) coating a composition for forming a resist underlayer film, which comprises (A) a polymer and (B) an organic solvent, on the substrate, and curing the composition by heat treatment at a temperature of 100° C. or higher and 800° C. or lower for 10 to 7,200 seconds to form an underlayer film precursor film; (ii) irradiating the substrate on which the underlayer film precursor film has been formed with plasma to form a resist underlayer film; A method for forming a resist underlayer film, comprising: The method for forming a resist underlayer film, wherein the polymer (A) contains a constitutional unit represented by the following general formula (1) and has a weight average molecular weight in terms of polystyrene of 2,500 to 20,000 as determined by a gel permeation chromatography method: 【Chemistry 1】 (In the formula, Ar １ and Ar ２ are independently a substituted or unsubstituted benzene ring or a substituted or unsubstituted naphthalene ring, X is a structure represented by the following general formula (1A), Y is a divalent organic group having 6 to 50 carbon atoms, and k is 0 or 1. 【Chemistry 2】 (In the formula, n １ is 0 or 1, n ２ is 1 or 2, R ２ R is either a hydrogen atom, an organic group having 1 to 10 carbon atoms, or a structure represented by the following general formula (1B): ３ is a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, or a group represented by the following general formula (1C), ３ is 0, 1, or 2, * is a bond to a methylene group, and ** is a bond to a quaternary carbon of fluorene. 【Chemistry 3】 (wherein * represents the bond site to the oxygen atom, R Ａ is a divalent organic group having 1 to 10 carbon atoms, R Ｂ is a hydrogen atom or a monovalent organic group having 1 to 10 carbon atoms. 【Chemistry 4】 (In the formula, R ４ is a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms, and the hydrogen atom on the benzene ring in the formula may be substituted with a methyl group or a methoxy group.

2. 2. The method for forming a resist underlayer film according to claim 1, wherein, in the general formula (1), Y is any one of structures represented by the following formula (Y-1): 【Chemistry 5】 (The hydrogen atoms in the above structure may be substituted with hydroxyl groups or monovalent organic groups having 1 to 10 carbon atoms.)

3. In the general formula (1A), R ２ 2. The method for forming a resist underlayer film according to claim 1, wherein is a hydrogen atom.

4. In the general formula (1A), R ２ is a hydrogen atom or a structure represented by the general formula (1B), ２ 2. The method for forming a resist underlayer film according to claim 1, wherein, in the structure constituting the above formula, a represents a ratio of hydrogen atoms, and b represents a ratio of the structure represented by the general formula (1B), the relationship of a+b=1 and 0.1≦b≦0.9 is satisfied.

5. In the general formula (1), Ar １ and Ar ２ 2. The method for forming a resist underlayer film according to claim 1, wherein: is an unsubstituted benzene ring; and in general formula (1A), n1 is 0, n2 is 1 or 2, and n3 is 0.

6. 2. The method for forming a resist underlayer film according to claim 1, wherein k is 0 in the general formula (1).

7. 2. The method for forming a resist underlayer film according to claim 1, wherein the polymer (A) has a weight average molecular weight in terms of polystyrene as determined by gel permeation chromatography of 7,000 to 15,000.

8. 2. The method for forming a resist underlayer film according to claim 1, wherein the composition for forming a resist underlayer film further contains one or more of a crosslinking agent (C), a surfactant (D), an acid generator (E), and a plasticizer (F).

9. The method for forming a resist underlayer film according to claim 1, characterized in that the (B) organic solvent is a mixture of one or more organic solvents having a boiling point of less than 180 degrees and one or more high-boiling point solvents (B-1) which are organic solvents having a boiling point of 180 degrees or more.

10. In the step (ii), the plasma irradiation is performed by N ２ , N.F. ３ , H ２ 10. The method for forming a resist underlayer film according to claim 1, wherein the method is carried out in an atmosphere of a fluorocarbon, a rare gas, or a mixture of any of these.

11. 10. The method for forming a resist underlayer film according to claim 1, wherein in the step (i), the heat treatment is performed in an atmosphere having an oxygen concentration of 1% or more and 21% or less.

12. 10. The method for forming a resist underlayer film according to claim 1, wherein in the step (i), the heat treatment is carried out in an atmosphere having an oxygen concentration of less than 1%.

13. A method for forming a pattern on a workpiece substrate, comprising the steps of: (I-1) A step of forming a resist underlayer film on a substrate to be processed by the method for forming a resist underlayer film according to any one of claims 1 to 9; (I-2) forming a resist intermediate film on the resist underlayer film; (I-3) forming a resist upper layer film on the resist intermediate film using a photoresist material; (I-4) a step of forming a pattern on the resist upper layer film by pattern-exposing the resist upper layer film and then developing the resist upper layer film with a developer; (I-5) a step of transferring the pattern to the resist intermediate film by dry etching using the resist upper layer film on which the pattern has been formed as a mask; (I-6) a step of transferring a pattern to the resist underlayer film by dry etching using the resist intermediate film to which the pattern has been transferred as a mask; and (I-7) A step of processing the substrate to be processed using the resist underlayer film on which the pattern has been formed as a mask to form a pattern on the substrate to be processed. A pattern forming method comprising the steps of:

14. A method for forming a pattern on a workpiece substrate, comprising the steps of: (II-1) A step of forming a resist underlayer film on a substrate to be processed having a step by the method for forming a resist underlayer film according to any one of claims 1 to 9; (II-2) forming a resist top layer film on the resist underlayer film; (II-3) a step of forming a pattern on the resist upper layer film by pattern-exposing the resist upper layer film and then developing the resist upper layer film with a developer; (II-4) a step of transferring the pattern to the resist underlayer film by dry etching using the resist upper layer film on which the pattern has been formed as a mask; (II-5) A step of processing the substrate to be processed using the resist underlayer film on which the pattern has been formed as a mask to form a pattern on the substrate to be processed. A pattern forming method comprising the steps of:

15. 15. The pattern formation method according to claim 14, wherein the aspect ratio of the step on the substrate to be processed is 3 or more.

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