JP2015129915A - Method for manufacturing transfer mask and developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transfer mask that decreases swelling of a resist pattern, pattern collapse, and distortion of a resist pattern, and forms a resist pattern having a linear pattern edge.SOLUTION: A method for manufacturing a transfer mask is provided, which includes steps of: preparing a substrate having a thin film; forming a resist film from a chemically amplified negative type resist solution on a surface of the thin film; exposing the resist film; developing the exposed resist film to form a resist pattern; and etching the thin film by using the resist pattern as a mask. In the step of forming the resist pattern, the developer used in a developing step comprises a solvent A and a solvent B that are both organic solvents, and a solvent C that is an organic solvent and less likely dissolves the resist film compared to the solvent A and the solvent B. The solvent A has a boiling point higher than that of the solvent C and the solvent C has a boiling point higher than that of the solvent B.

Description

  The present invention relates to a transfer mask manufacturing method and developer, and more particularly to a transfer mask manufacturing method and developer applied when forming a resist pattern from a resist film formed of a chemically amplified and negative resist solution. About.

  Generally, in a manufacturing process of a semiconductor device or the like, a fine pattern is formed using a photolithography method. A transfer mask is used in the fine pattern transfer process when the photolithography method is performed. This transfer mask is generally manufactured by forming a desired fine pattern (uneven pattern) on a light shielding film of a mask blank as an intermediate. In order to form a desired fine pattern on the light shielding film, a resist film is formed so as to cover the light shielding film. In order to fabricate a transfer mask from a mask blank, first, exposure corresponding to a predetermined shape is performed on a resist film, and then development is performed to form a resist pattern having irregularities from the resist film. Then, using the resist pattern as a mask, the light shielding film is etched to form a desired fine pattern on the light shielding film.

  A resist solution is used when forming a resist film on the surface of the mask blank. There are various types of resist solutions. For example, there is a positive resist solution in which the exposed portion can be dissolved, and conversely, a negative resist solution in which the exposed portion is cured and cannot be dissolved.

  When a positive resist solution is used, the exposed portion becomes a light transmitting portion in the transfer mask. At present, the movement to enlarge the light transmitting portion is becoming popular. However, if the light transmission part is to be enlarged, the exposed part must be enlarged naturally. If exposure is performed by drawing like electron beam drawing, a very long time is required to complete the exposure.

  On the other hand, when a negative resist solution is used, a portion that has not been exposed becomes a light transmitting portion in the transfer mask. Therefore, in order to increase the light transmission portion, it is only necessary to reduce the exposure portion. That is, if the exposure is performed by drawing like electron beam drawing, the time required to complete the exposure is very small. Therefore, in recent years, the frequency of using a negative resist solution in the manufacturing process of a transfer mask or the like is increasing.

However, Patent Documents 1 and 2 provide points to be noted when developing a resist film using a negative resist solution.
In other words, if the affinity between the developer used in the development of the resist film and the resist film is high, the developer (exposure part) in the resist pattern is hardened and insoluble by the exposure. May swell. When the resist pattern swells, for example, the pattern is unevenly deflated at the time of drying, and depressions and protrusions are formed on the convex portions, so that the line width uniformity in plan view is significantly reduced. As a result, when conductive portions having a shape corresponding to a resist pattern are formed in the future in a transfer mask or the like, conductive portions that are adjacent but separated from each other are formed adjacent to each other beyond imagination. There is also a risk of performance degradation such as short circuit.
In addition, due to the high affinity between the developer and the resist film, a so-called undercut phenomenon occurs in which the root of the convex portion in the resist pattern (the portion in contact with the underlying light-shielding film) is melted more than expected. Pattern collapse may occur.

  In order to eliminate the fear, in Patent Documents 1 and 2, as a developing solution, a good solvent having a low boiling point (a solvent having a high affinity with a resist film) and a poor solvent having a high boiling point (having an affinity for a resist film). A low solvent). By doing so, first, since the proportion of the good solvent in the developer is reduced, the resist pattern is relatively less likely to swell, and the resist pattern is prevented from being smeared.

JP 2011-65105 A JP 2013-7785 A

  As a result of the study of the techniques described in Patent Documents 1 and 2 above, the following problems were newly clarified.

  The problem is, as shown in FIG. 3B (corresponding to a comparative example of the present specification, which will be described later), for example, distortion (“swell”) or “ It is also called “gagged”.).

  According to the above-mentioned Patent Documents 1 and 2, the major problems of resist pattern swelling and pattern collapse are certainly solved. On the other hand, the performance of a semiconductor device or the like manufactured using a transfer mask is improving day by day, and the required performance is also increasing day by day. In such a situation, the distortion described above may affect LER (Line Edge Roughness), which is one index for evaluating the shape of the resist pattern, so that the performance of the semiconductor device or the like is maximized. May also be affected.

  An object of the present invention is to provide a technique for reducing a resist pattern swelling, pattern collapse, and resist pattern distortion, and forming a resist pattern having linear pattern edges.

  The present inventor has studied a technique for solving the above-described problems. At that time, the techniques described in Patent Documents 1 and 2 described above are effective techniques for suppressing the swelling of the resist pattern and the occurrence of pattern collapse. The cause was examined. As a result, the present inventor obtained the following knowledge.

  That is, according to the techniques described in Patent Documents 1 and 2, since the boiling point of the good solvent is relatively low, the good solvent volatilizes in the initial stage of the drying process. In other words, the good solvent will volatilize without fully dissolving the soluble part (non-exposed part) of the negative resist film, which may cause jaggedness when the resist pattern is viewed in plan. The inventor speculated.

  Further, in the techniques described in Patent Documents 1 and 2, since the good solvent quickly volatilizes first from the convex portion of the resist pattern that absorbs some good solvent even if it does not swell, the convex The present inventor has speculated that the portion may be rapidly squeezed and waviness may occur when the convex portion of the resist pattern is viewed in plan.

  Based on the above findings, the present inventor has studied. As a result, in addition to “a good solvent having a low boiling point” and “a poor solvent having a high boiling point”, a method of adding “a good solvent having a higher boiling point” as a component of the developer was devised. By doing this, the method of suppressing the rapid dent of the resist pattern while leaving the good solvent on the resist pattern until the final stage in the drying process and sufficiently dissolving the soluble part of the negative resist film. I came up with it.

  The configuration of the present invention based on this finding is as follows.

<Configuration 1>
The first configuration of the present invention is a method for manufacturing a transfer mask.
The manufacturing method includes a step of preparing a substrate having a thin film, a step of forming a resist film on the surface of the thin film, a step of exposing the resist film, and a step of developing the resist film after exposure. A step of forming a resist pattern by performing and a step of etching the thin film using the resist pattern as a mask are included.
In the step of forming the resist pattern, the resist film is a resist film formed with a chemically amplified and negative resist solution.
In the production method of the present invention, the developer used when performing the developing step is an organic solvent, that is, the solvent A and the solvent B, and the organic solvent, compared to the solvent A and the solvent B. A solvent C that hardly dissolves the resist film is included, the boiling point of the solvent A is higher than that of the solvent C, and the boiling point of the solvent C is higher than that of the solvent B.
According to this configuration, by including a poor solvent having low affinity with the resist, infiltration of the developer into the resist pattern is suppressed, and problems such as swelling of the resist pattern and accompanying collapse can be suppressed. Furthermore, by adding a slightly good solvent having a boiling point higher than that of the poor solvent, the pattern edge can be smoothed at the final stage of drying of the developer.
Here, the “good solvent” is a solvent that can dissolve the resist composition before exposure while maintaining a chemically stable state, and the dissolution rate with respect to the resist film is preferably 5 nm / sec or more at 23 ° C. Means 10 nm / sec or more, more preferably 12 nm / sec or more. The “poor solvent” refers to a solvent that cannot dissolve the resist composition before exposure. For example, when the resist composition solution is diluted 10 times or more with the poor solvent, the diluted solution is deposited by the precipitation of the resist composition. A solvent that can be turbid. The specific poor solvent has a specific dissolution rate with respect to the resist film of 1 nm / sec or less, preferably 0.5 nm / sec or less, more preferably 0.3 nm / sec or less. A particularly preferable solvent that does not dissolve is 0.01 nm / sec or less.

<Configuration 2>
According to a second configuration of the present invention, in the configuration described in the first configuration, the dissolution rate of the solvent A and the solvent B in the resist film is 10 nm / sec or more at 23 ° C. The film is dissolved at a rate of 0.5 nm / sec or less at 23 ° C.
When the dissolution rates of the solvent A and the solvent B, which are good solvents, are within the above range, the development rate can be maintained even when the solvent C is mixed with the solvent C, which is a poor solvent. Also. If the dissolution rate of the solvent C, which is a poor solvent, is in the above range, the solvent C does not substantially penetrate into the exposed portion of the resist film, so that the phenomenon such as swelling by the developer is more effectively suppressed. Can do.
In the case of a good solvent, the higher the dissolution rate in the resist film, the better. In the case of a poor solvent, the lower the dissolution rate in the resist film, the better. Accordingly, the upper limit value of the dissolution rate of the good solvent is not particularly limited, and the lower limit value of the dissolution rate of the poor solvent is not particularly limited. However, if a specific lower limit value is set, the lower limit value is set to the resist film. The dissolution rate is 0 nm / sec.

<Configuration 3>
A third configuration of the present invention is the configuration described in the first or second, wherein the solvent B has a higher dissolution rate in the resist film than the solvent A.
Although the solvent A and the solvent B are good solvents, among them, the role sharing between the solvent A and the solvent B can be clarified by increasing the dissolution rate of the solvent B in the resist film. . That is, the solvent B is a main solvent that dissolves the resist film, but has a low boiling point and is relatively volatile. On the other hand, the solvent A does not dissolve the resist film as easily as the solvent B, but has a high boiling point and is relatively difficult to volatilize, and contributes to pattern edge smoothing in the drying process after development.

<Configuration 4>
According to a fourth aspect of the present invention, there is provided the structure according to any one of the first to third aspects, wherein the volume fraction of the solvent A in the developer is 5% or more and 10% or less. .
When the ratio of the solvent A contained in the developer is within the above range, smoothing of the pattern edge is effected without causing the resist pattern to swell due to the component of the good solvent remaining at the final stage of the volatilization of the developer. Can be done automatically.

<Configuration 5>
A fifth configuration of the present invention is the configuration according to any one of the first to fourth, wherein the boiling point of the solvent A is 140 ° C. or higher and 250 ° C. or lower.
The solvent A contributes to pattern edge smoothing in the drying step after development. If the volatilization of the solvent A is too early, smoothing becomes insufficient and distortion occurs. Conversely, if it is too slow, the smoothing is excessively performed and the pattern edge is rounded. However, when the boiling point of the solvent A is in the above range, a pattern having a linear shape and a rectangular cross section can be formed by smoothing.

<Configuration 6>
A sixth configuration of the present invention is the configuration according to any one of the first to fifth aspects, wherein at least one of the solvent A and the solvent B is at least one of the solvents constituting the resist solution. It is characterized by being the same kind as a kind.
The solvent constituting the resist solution can stably maintain the dissolved state of the resist composition without changing the structure of the resist composition that is the solute of the resist solution. When such a solvent is contained in the component of the developing solution, when a resist pattern is formed by development using an organic solvent, the non-exposed portion of the resist film can be surely eluted. At the same time, the exposed portion (resist pattern) in the resist film is preferable because it does not cause a chemical change. In addition, it is preferable that at least the solvent B is the same as at least one of the solvents constituting the resist solution.

<Configuration 7>
A seventh configuration of the present invention is the configuration according to any one of the first to sixth, wherein the volume fraction of the solvent C in the developer is 30% or more.
If the solvent C, which is a poor solvent, is 30% or more, since the developer is prevented from penetrating into the exposed portion of the resist pattern during development, the swelling of the resist pattern is more effectively suppressed.

<Configuration 8>
An eighth configuration of the present invention is the configuration according to any one of the first to seventh aspects, wherein the volume fraction of the solvent C in the developer is 50% or more.
If the solvent C, which is a poor solvent, is 50% or more, it is more reliably suppressed that the developing solution penetrates into the exposed portion of the resist pattern during development, and thus the resist pattern is particularly effectively prevented from swelling.

<Configuration 9>
A ninth configuration of the present invention is the configuration according to any one of the first to eighth aspects, wherein in the step of etching the thin film, dry etching using a reactive gas as an etchant is performed, and the reactive gas is added to the reactive gas. Is characterized by containing an isotropic etching gas.
The term “isotropic etching gas” as used herein refers to an etching gas not only in the thickness direction of the thin film but also on the side wall of the pattern during formation when the thin film is etched to form an uneven pattern on the thin film (patterning). Refers to the gas that acts. In this case, the etching rate in the thickness direction of the thin film and the etching rate to the side wall may not be equal.
When an isotropic etching gas is included in the etching gas used for patterning the thin film, the formed thin film pattern tends to have a pattern shape that synergistically reflects the distortion shape of the resist pattern. In the present invention, since distortion of the resist pattern is suppressed, a linear thin film pattern can be formed even if the etching gas used for thin film patterning is isotropic.

<Configuration 10>
A tenth configuration of the present invention is the configuration according to ninth, wherein the composition of the surface layer of the thin film contains chromium, and the reactive gas is a mixed gas containing at least oxygen and chlorine. Features.
The layer containing chromium in the composition has etching selectivity with respect to the layer containing silicon in the composition, and thus is easily applied to the surface layer of the thin film because it is applied to a hard mask or the like of the layer containing silicon in the composition. The layer containing chromium is etched by dry etching using a mixed gas containing chlorine and oxygen, but the mixed gas containing chlorine and oxygen is isotropic, so that the resist pattern shape as a mask is formed. If there is distortion or the like, the resulting thin film pattern will be formed in a shape that is synergistic with the distortion of the resist pattern.
Since the structure of the present invention suppresses resist pattern distortion, etc., even when a mixed gas of oxygen and chlorine is used as an etching gas with a thin film of a surface layer containing chromium, a linear thin film pattern Can be formed.

<Configuration 11>
An eleventh configuration of the present invention is a developer used when a developing process is performed as a resist pattern is formed from a resist film formed by a chemically amplified and negative resist solution.
The developer of the present invention contains the solvent A and the solvent B which are organic solvents, and the solvent C which is an organic solvent and hardly dissolves the resist film as compared with the solvent A and the solvent B. The developing solution is characterized in that the boiling point of A is higher than that of the solvent C, and the boiling point of the solvent C is higher than that of the solvent B.
By using this developing solution, even if a developing process using an organic solvent is employed and a resist pattern is formed using a negative resist, swelling of the resist pattern can be effectively suppressed and linear A resist pattern having a pattern edge can be formed.

  ADVANTAGE OF THE INVENTION According to this invention, the technique which reduces the swelling of a resist pattern, pattern collapse, and the distortion of a resist pattern, and forms the resist pattern which has a linear pattern edge can be provided.

It is process drawing of the manufacturing method of the transfer mask in this embodiment. In a present Example, it is a graph which shows a result at the time of setting a horizontal axis | shaft to exposure intensity | strength (DOSE amount) and making a vertical axis | shaft into a residual film rate. It is an electron micrograph which shows a mode that the resist pattern was expanded in the Example (FIG. 3 (a)) and the comparative example (FIG.3 (b)).

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In the present embodiment, description will be given in the following order.
1. Manufacturing Method of Transfer Mask 1-A) Substrate with Thin Film (Mask Blank) Preparation Step 1-Aa) Substrate Preparation Step 1-Ab) Thin Film Formation Step 1-B) Resist Film Formation Step 1-C) Exposure Step 1-D) Development step 1-E) Etching step 1-F) Others Effects According to Embodiments For configurations not described below, known configurations may be adopted as appropriate.

<1. Method for Manufacturing Transfer Mask 50>
A method for manufacturing the transfer mask 50 in the present embodiment will be described with reference to FIG. FIG. 1 is a process diagram of a method for manufacturing a transfer mask 50 in the present embodiment. In the present embodiment, an example in which the substrate 10 is prepared and the thin film 11 is formed on the substrate 10 in the substrate-preparing step with the thin film is shown, but a mask blank 5 on which the thin film 11 is formed in advance is prepared. A form in which a resist film is formed thereon is also included in the form of the present invention.

1-A) Substrate with Thin Film (Mask Blank) Preparation Step 1-Aa) Substrate Preparation Step First, the substrate 10 used for the transfer mask 50 is prepared. As the substrate 10 of the transfer mask 50, a glass substrate can be used. In the case of a transmissive mask, the substrate 10 is selected from a glass material having a high transmittance with respect to exposure light when forming a pattern on the wafer. In the case of a reflective mask, a low thermal expansion glass that can minimize the thermal expansion of the substrate 10 due to the energy of exposure light is selected.
Specifically, in the case of a transmission type mask (for example, a binary mask, a phase shift mask, and a gray tone mask), the material of the substrate 10 is synthetic quartz glass, soda lime glass, aluminosilicate glass, borosilicate glass, non-alkali. Glass etc. are mentioned. As a detailed example, a synthetic quartz glass having a high transmittance with respect to light with a wavelength of 300 nm or less is preferably used for the substrate 10 of a transfer mask that uses an ArF excimer laser with a wavelength of 193 nm or a KrF excimer laser with a wavelength of 254 nm as exposure light. be able to.
In the case of an EUV mask which is a reflective mask, the substrate 10 is more preferably within a range of about 0 ± 1.0 × 10 ⁻⁷ / ° C. in order to suppress distortion of the transferred pattern due to heat during exposure. Is preferably a SiO ₂ —TiO ₂ glass, which is a glass material having a low thermal expansion coefficient within a range of about 0 ± 0.3 × 10 ⁻⁷ / ° C.

1-Ab) Thin Film Formation Step Next, the thin film 11 is formed on the main surface of the substrate 10 as shown in FIG. The thin film 11 formed on the surface of the substrate 10 and under the resist film 12 is the thin film 11 selected according to the use of the transfer mask 50 to be manufactured. If it enumerates, the following (1)-(5) will be mentioned.

(1) Thin film of binary mask When producing a binary mask blank, the thin film 11 which has a light shielding film is formed on the board | substrate 10 which has translucency with respect to the light of exposure wavelength.
This light shielding film is made of a material containing a transition metal alone or a compound thereof such as chromium, tantalum, ruthenium, tungsten, titanium, hafnium, molybdenum, nickel, vanadium, zirconium, niobium, palladium, rhodium. For example, a light-shielding film composed of chromium or a chromium compound in which one or more elements selected from elements such as oxygen, nitrogen, and carbon are added to chromium. Further, for example, a light shielding film composed of a tantalum compound in which one or more elements selected from elements such as oxygen, nitrogen, and boron are added to tantalum.
Further, the thin film 11 has a light-shielding film having a two-layer structure of a light-shielding layer and a front-surface antireflection layer, or a three-layer structure in which a back-surface antireflection layer is added between the light-shielding layer and the substrate 10. is there. Moreover, it is good also as a composition gradient film | membrane from which the composition in the film thickness direction of a light shielding film differs continuously or in steps.
Moreover, it is good also as a structure of the thin film 11 which has an etching mask film | membrane on a light shielding film. This etching mask film has etching selectivity (etching resistance) with respect to etching of the light-shielding film containing transition metal silicide, and in particular, chromium, or a chromium compound in which elements such as oxygen, nitrogen, and carbon are added to chromium. It is preferable to use a material. At this time, the transfer mask 50 may be manufactured with the etching mask film remaining on the light shielding film by providing the etching mask film with an antireflection function.

(2) Thin film of binary mask having other configuration As another example of thin film 11 of binary mask, a light shielding film made of a material containing a compound of transition metal and silicon (including transition metal silicide, particularly molybdenum silicide). The structure which has can also be mentioned.
This light-shielding film is made of a material containing a compound of a transition metal and silicon, and examples thereof include a material mainly composed of these transition metal and silicon and oxygen and / or nitrogen. Examples of the light shielding film include a material mainly composed of a transition metal and oxygen, nitrogen, and / or boron. As the transition metal, molybdenum, tantalum, tungsten, titanium, hafnium, nickel, vanadium, zirconium, niobium, palladium, ruthenium, rhodium, chromium, or the like is applicable.
In particular, when the light shielding film is formed of a molybdenum silicide compound, a two-layer structure of a light shielding layer (MoSi or the like) and a surface antireflection layer (MoSiON or the like), or a back surface reflection between the light shielding layer and the substrate 10. There is a three-layer structure to which a prevention layer (MoSiON or the like) is added.
Moreover, it is good also as a composition gradient film | membrane from which the composition in the film thickness direction of a light shielding film differs continuously or in steps.

(3) Thin film of halftone type phase shift mask When producing a halftone type phase shift mask, transition metal and silicon (transition metal silicide) are formed on a substrate 10 that is transparent to the wavelength of exposure light used during transfer. The thin film 11 having a light semi-transmissive film made of a material containing a compound (including molybdenum silicide in particular) is formed.
The light semi-transmissive film included in the thin film 11 transmits light having an intensity that does not substantially contribute to exposure (for example, 1% to 30% with respect to the exposure wavelength), and has a predetermined phase difference (for example, 180%). Degree). The halftone phase shift mask includes a light semi-transmission part obtained by patterning the light semi-transmission film, and a light transmission part that does not have the light semi-transmission film and that transmits light having an intensity that substantially contributes to exposure. Thus, the phase of the light is transmitted through the light semi-transmissive part and the phase of the light is substantially inverted with respect to the phase of the light transmitted through the light transmissive part. Lights that pass through the vicinity of the boundary part and enter each other's areas due to the diffraction phenomenon cancel each other, so that the light intensity at the boundary part is almost zero, and the contrast of the boundary part, that is, the resolution is improved.
This light semi-transmissive film is made of a material containing a compound of, for example, a transition metal and silicon (including a transition metal silicide), and includes a material mainly composed of these transition metal and silicon, and oxygen and / or nitrogen. . As the transition metal, molybdenum, tantalum, tungsten, titanium, hafnium, nickel, vanadium, zirconium, niobium, palladium, ruthenium, rhodium, chromium, or the like is applicable.
In the case of having a light-shielding film on the light semi-transmissive film, the material of the light semi-transmissive film contains a transition metal and silicon. It is preferable to have chromium (having etching resistance), particularly chromium, or a chromium compound in which elements such as oxygen, nitrogen, and carbon are added to chromium.

(4) Thin film of multi-tone mask The thin film 11 of the multi-tone mask has a laminated structure of one or more semi-transmissive films and a light shielding film.
As for the material of the semi-transmissive film, in addition to the same elements as the light semi-transmissive film of the halftone phase shift mask blank described above, there are also materials containing simple metals such as chromium, tantalum, titanium, aluminum, alloys, or compounds thereof. included.
The composition ratio and film thickness of each element are adjusted so as to have a predetermined transmittance with respect to the exposure light. As the light shielding film material, the light shielding film of the binary mask blank can be applied. However, the composition of the light shielding film material and the light shielding film material can have a predetermined light shielding performance (optical density) in a laminated structure with the semi-transmissive film. The film thickness is adjusted.

(5) Thin film of reflective mask In the thin film 11 of the reflective mask, a multilayer reflective film that reflects exposure light is formed on the substrate 10, and an absorber film that absorbs exposure light is formed in a pattern on the multilayer reflective film. Has a structured. Light (EUV light) incident on a reflective mask mounted on an exposure machine (pattern transfer device) is absorbed by a portion having an absorber film and reflected by a multilayer reflective film in a portion having no absorber film. Is transferred onto the semiconductor substrate 10 through the reflection optical system.
The multilayer reflective film is formed by alternately laminating high refractive index layers and low refractive index layers. Examples of the multilayer reflective film include Mo / Si periodic multilayer films, Ru / Si periodic multilayer films, Mo / Be periodic multilayer films, and Mo compound / Si compound periodic multilayer films in which Mo films and Si films are alternately stacked for about 40 periods. Si / Nb periodic multilayer film, Si / Mo / Ru periodic multilayer film, Si / Mo / Ru / Mo periodic multilayer film, Si / Ru / Mo / Ru periodic multilayer film, and the like. The material can be appropriately selected depending on the exposure wavelength.
The absorber film has a function of absorbing exposure light such as EUV light, and for example, tantalum (Ta) alone or a material mainly composed of Ta can be preferably used. Such an absorber film preferably has an amorphous or microcrystalline structure in terms of smoothness and flatness.

1-B) Resist Film Formation Step Next, as illustrated in FIG. 1B, a resist film 12 is formed on the thin film 11 of the mask blank 5. The resist film 12 is formed of a chemically amplified and negative resist solution. As the resist solution, a known solution may be used as long as it is chemically amplified and negative. Examples of substances constituting the resist film 12 include the following.

  The resist solution in this embodiment contains at least a base polymer, a photoacid generator, a crosslinking agent that crosslinks the base polymer by the action of an acid, and a solvent.

  The base polymer is not particularly limited as long as it is a polymer having a functional group capable of being cross-linked when a cross-linking reaction by a cross-linking agent starts with generation of an acid. Specific examples include polyhydroxystyrene resins, novolac resins, acrylic resins, and the like having a polar group (for example, a carboxyl group, an alkoxyl group, a hydroxyl group, and an alkoxycarbonyl group). This embodiment is particularly effective with respect to a polyhydroxystyrene-based polymer.

The cross-linking agent is a cross-linking agent having a functional group capable of cross-linking with the base polymer, and is composed of a substance that exhibits cross-linking ability by the action of an acid.
Examples of the functional group include a hydroxymethyl group, an alkoxymethyl group, an acyloxymethyl group, or an alkoxymethyl ether group, and a compound or resin having two or more of these.

  The acid generator is not particularly limited as long as it is a known acid generator, but generates at least one of sulfonic acid, bis (alkylsulfonyl) imide, or tris (alkylsulfonyl) methide by irradiation with actinic rays or radiation. Compounds are preferred.

  The solvent that can be used in preparing the composition is not particularly limited as long as it dissolves each component. For example, alkylene glycol monoalkyl ether carboxylate (propylene glycol monomethyl ether acetate (PGMEA; 1-methoxy-2 -Acetoxypropane), etc.), alkylene glycol monoalkyl ether (propylene glycol monomethyl ether (PGME; 1-methoxy-2-propanol: BP119 ° C.) etc.), alkyl lactate (ethyl lactate, methyl lactate etc.), cyclic lactone (γ- Butyrolactone, preferably 4 to 10 carbon atoms, chain or cyclic ketone (2-heptanone, cyclohexanone, etc., preferably 4 to 10 carbon atoms), alkylene carbonate (ethylene carbonate, propylene) Carbonate, etc.), alkyl acetate such as carboxylic acid alkyl (butyl acetate is preferred), and the like alkoxy alkyl acetates (ethyl ethoxypropionate). In particular, PGMEA and PGME are preferable.

The composition may contain other components such as a surfactant, a basic component, a sensitizer, a light absorbing material, and an antioxidant.
A specific method for forming the resist film 12 may be a known method. For example, the resist blank may be spin-coated on the surface of the mask blank 5 and then baked.

  The resist mask blank 1 used for manufacturing the transfer mask 50 is thus manufactured.

1-C) Exposure Step Next, as shown in FIG. 1C, the formed resist film 12 is exposed in a predetermined shape. As a specific exposure method, a known method may be used. For example, you may employ | adopt the exposure method used for each mask quoted at the 1-Ab) thin film formation process.

1-D) Development Step One of the major features of this embodiment is the development step. A resist pattern is formed by the development process as shown in FIG. A known method may be used for the specific operation of the development process. However, the developer used in this step is composed of at least solvent A and solvent B, which are organic solvents, and solvent C, which is an organic solvent and hardly dissolves resist film 12 as compared with solvent A and solvent B. ing. The solvent A has a boiling point higher than that of the solvent C, and the solvent C has a boiling point higher than that of the solvent B. Hereinafter, the solvent A and the solvent B are referred to as “good solvent”, and the solvent C is referred to as “poor solvent”.

[Components of good solvent A]
As the good solvent A, an ester solvent, a ketone solvent, a glycol ether solvent, an alcohol solvent, and a polar solvent ester solvent such as an ether solvent can be used. A good solvent A having a boiling point higher than that of the poor solvent C may be used. In addition, when the poor solvent C consists of a plurality of types of solvents, the good solvent A has a higher boiling point than the solvent having the highest boiling point among the plurality of types of solvents. A preferred solvent is a solvent having a property that the difference in boiling point between the poor solvent C and the good solvent A is 2 ° C. or more and less than 20 ° C., and a particularly preferred solvent is a difference in boiling point between the poor solvent C and the good solvent A of 3 It is a solvent having a property that is at least 10 ° C. If the difference in boiling point between the poor solvent C and the good solvent A is less than 2 ° C., the good solvent A will be volatilized immediately after the volatilization of the poor solvent C is completed. There is a risk that smoothing will be insufficient. Moreover, when the boiling point of the good solvent A is 20 ° C. or more higher than the boiling point of the poor solvent C, it takes time for the good solvent A to volatilize, and there is a concern that the drying process takes a long time. In consideration of the above, the boiling point of the solvent A is preferably 140 ° C. or higher and 250 ° C. or lower.

(Ester solvent)
Examples of ester solvents include propylene glycol monomethyl ether acetate (PGMEA), amyl acetate, ethyl lactate, ethylene glycol monoethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl methoxypropionate, ethyl 3-ethoxypropionate, ethoxy Ethyl propionate, 3-methoxybutyl acetate, methyl acetoacetate, ethyl acetoacetate, butyl lactate, ethylene glycol monobutyl ether acetate, 3-methyl-3-methoxybutyl acetate, diethylene glycol monoethyl ether acetate, and butyl carbitol acetate Can be mentioned. Can be mentioned.
Among them, amyl acetate, propylene glycol monomethyl ether acetate (PGMEA; 1-methoxy-2-acetoxypropane), propylene glycol monoethyl ether acetate, ethyl lactate, ethylene glycol monoethyl ether acetate, 3-methoxybutyl acetate, diethylene glycol monoethyl ether Acetate, butyl lactate and propylene glycol diacetate are preferred.

(Ketone and alkyl ketone solvents)
Examples of ketone solvents include acetylacetone, 4-heptanone, cyclohexanone, methylcyclohexanone, 1-octanone, 2-octanone, cycloheptanone, acetonylacetone, 2-nonanone, acetophenone, isophorone, phenylacetone, ionone, propylene. Examples thereof include carbonate and methyl amyl ketone. Of these, acetylacetone, 4-heptanone, cyclohexanone, methylcyclohexanone, 1-octanone, 2-octanone, cycloheptanone, acetonylacetone, and 2-nonanone are preferable.

(Glycol ether solvent)
Examples of the glycol ether solvent include propylene glycol propyl ether, ethylene glycol t-butyl ether, 3-methoxybutanol, diethylene glycol dimethyl ether, propylene glycol monobutyl ether, ethylene glycol monobutyl ether, dipropylene glycol dimethyl ether, 3-methyl-3-methoxybutanol, Diethylene glycol ethyl methyl ether, diethylene glycol isopropyl methyl ether, dipropylene glycol monomethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol monohexyl ether, dipropylene glycol propyl ether, diethylene Recall butyl methyl ether, tripropylene glycol dimethyl ether, triethylene glycol dimethyl ether, ethylene glycol 2-ethyl hexyl ether, diethylene glycol monobutyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, ethylene glycol phenyl ether, and triethylene glycol monomethyl Ether.
Among these, propylene glycol monoethyl ether, diethylene glycol dimethyl ether, propylene glycol monobutyl ether, 3-methyl-3-methoxybutanol, dipropylene glycol monomethyl ether, and diethylene glycol monomethyl ether are preferable.

(Alcohol solvent)
Examples of the alcohol solvent include n-hexyl alcohol, methoxymethylbutanol, n-heptyl alcohol, phenol, 2 ethyl-hexanol, 1,2-propylene glycol, n-octyl alcohol, ethylene glycol, 1,3-butylene glycol. 1,3-propylene glycol, 1,4-butylene glycol, n-decanol, diethylene glycol and the like. Among these, n-hexyl alcohol, methoxymethylbutanol, n-heptyl alcohol, 2 ethyl-hexanol, 1,2-propylene glycol, n-octyl alcohol, and ethylene glycol are preferable.

[Components of good solvent B]
As the good solvent, an ester solvent, a ketone solvent, and a polar solvent ester solvent such as an ether solvent can be used. As the good solvent B, a solvent having a lower boiling point than that of the poor solvent C may be used. In addition, when the poor solvent C consists of a plurality of types of solvents, the boiling point of the good solvent B is set lower than that of the plurality of types of solvents having the lowest boiling point. A preferred solvent is a solvent having a property that the difference in boiling point between the poor solvent C and the good solvent B is 50 ° C. or more and 5 ° C. or less, and a particularly preferred solvent is 30 ° C. or more and 10 ° C. or less than the boiling point of the poor solvent C. It is a solvent of some nature. If the difference in boiling point between the poor solvent C and the good solvent B is less than 5 ° C., the poor solvent C will be volatilized together with the volatilization of the good solvent B. The pattern can swell. Moreover, when the difference in boiling point between the poor solvent C and the good solvent B is 50 ° C. or more, there is a concern that it takes time for the poor solvent C to volatilize and the drying process takes a long time. In consideration of the above, the boiling point of the solvent B is preferably 70 ° C. or higher (preferably 80 ° C. or higher) and 170 ° C. or lower.

  The good solvent B preferably has a higher dissolution rate in the resist film 12 than the good solvent A. The good solvent A and the good solvent B are both good solvents. Among them, the role of the good solvent A and the good solvent B is clarified by increasing the dissolution rate of the good solvent B in the resist film. It becomes possible to do. That is, the solvent B is a main solvent that dissolves the resist film, but has a low boiling point and is relatively volatile. On the other hand, the solvent A does not dissolve the resist film as easily as the solvent B, but has a high boiling point and is relatively difficult to volatilize, and contributes to pattern edge smoothing in the drying process after development.

  Moreover, it is good also as a structure of the thin film 11 which has an etching mask film | membrane on a light shielding film. This etching mask film has etching selectivity (etching resistance) with respect to etching of the light-shielding film containing transition metal silicide, and in particular, chromium, or a chromium compound in which elements such as oxygen, nitrogen, and carbon are added to chromium. It is preferable to use a material. At this time, the transfer mask 50 may be manufactured with the etching mask film remaining on the light shielding film by providing the etching mask film with an antireflection function.

  In addition, it is preferable that the solvent B is the same type as the solvent that constitutes the resist solution, or when there are a plurality of solvents that constitute the resist solution, the solvent B is the same type as at least one of the plurality of solvents. Here, “same kind” indicates that the solvent B and the resist film 12 use solvents having the same composition. Since the affinity between the solvent B and the resist film 12 is increased, dissolution in the resist film 12 after exposure can be promoted, and generation of residual dissolution of the resist film 12 can be suppressed.

  The same applies to the solvent A. That is, it is preferable that at least one of the solvent A and the solvent B is the same as at least one of the solvents constituting the resist solution.

  Of course, high affinity between the solvent B and the resist film 12 leads to swelling of the resist pattern. Therefore, in the present embodiment, the boiling point of the solvent B is set to be the lowest among the solvents A to C, and is quickly removed from the resist pattern in the drying process.

(Ester solvent)
Examples of ester solvents for solvent B include ethyl acetate, propyl formate, isopropyl acetate, isopropyl acetate, n propyl acetate, butyl formate, isobutyl acetate, butyl acetate, amyl acetate, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate ( PGMEA), amyl acetate, ethyl lactate, ethylene glycol monoethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl methoxypropionate, ethyl 3-ethoxypropionate, ethyl ethoxypropionate, 3-methoxybutyl acetate, methyl acetoacetate Is mentioned.
Of these, butyl acetate, amyl acetate, propylene glycol monomethyl ether acetate (PGMEA; 1-methoxy-2-acetoxypropane), propylene glycol monoethyl ether acetate, and ethyl ethoxypropionate are preferable. Note that PEGMEA is known as a raw material for a resist solution, as shown in [0130] of Patent Document 2.

(Ketone and alkyl ketone solvents)
Examples of the solvent B ketone and alkyl ketone solvents include, for example, methyl ethyl ketone, methyl isobutyl ketone, methyl isobutyl ketone, 3-hexanone, diisobutyl ketone, 2-hexanone, cyclopentanone, acetylacetone, methyl amyl ketone, 4-heptanone, And cyclohexanone.
Among these, methyl isobutyl ketone, 3-hexanone, diisobutyl ketone, 2-hexanone, cyclopentanone, acetylacetone, methyl amyl ketone, and 4-heptanone are preferable.

(Glycol ether solvent)
Examples of the glycol ether solvent include ethylene glycol dimethyl ether, ethylene glycol dimethyl ether, propylene glycol dimethyl ether, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether (PGME), ethylene glycol monoethyl ether, ethylene glycol isopropyl ether. , Propylene glycol propyl ether, ethylene glycol t-butyl ether, 3-methoxybutanol, diethylene glycol dimethyl ether, propylene glycol monobutyl ether. Among these, propylene glycol monomethyl ether, ethylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether, and ethylene glycol monoethyl ether are preferable.

(Ether solvent)
Examples of the ether solvent of the solvent B include tetrahydropyran and 1,4-dioxane.

(Alcohol solvent)
Examples of the alcohol solvent of the solvent B include isopropyl alcohol, tert-butyl alcohol, cresol, n-propyl alcohol, sec-butyl alcohol, isobutyl alcohol, n-butyl alcohol, and n-hexyl alcohol.
Of these, cresol, n-propyl alcohol, sec-butyl alcohol, and isobutyl alcohol are preferable.

[Components of poor solvent C]
As the poor solvent C, a nonpolar solvent having a boiling point of 100 ° C. or higher and lower than 230 ° C. is preferably selected. It is preferable to use aliphatic hydrocarbons and aromatic hydrocarbons having the above boiling range properties as nonpolar solvents. If it exceeds 230 ° C., it takes time for the drying process after development. Moreover, excessive evaporation of a developing solution can be suppressed by setting it as 100 degreeC or more. The poor solvent C has a boiling point of preferably 120 ° C. or higher and lower than 230 ° C., particularly preferably 130 ° C. or higher and lower than 200 ° C.

Examples of the aliphatic hydrocarbon of the poor solvent C include alkanes having 7 to 12 carbon atoms, alkenes, allenes, and cycloalkanes. For example, as examples of alkanes and cycloalkanes, butylcyclohexane, cyclononane, diethylcyclohexane, n-undecane, n-decane, 1-methyl-4-isopropylcyclohexane, methylnonane, tetramethylcyclohexane, cyclooctane, n-nonane, Examples thereof include trimethylheptane, isoptylcyclopentane, trimethylcyclohexane, methyloctane, trimethylhexane, ethylcyclohexane, isopropylcyclopentane, and n-octane. Examples of alkenes and allenes include 1-nonene, dimethylheptene, octene, dimethylhexene, dimethyloctadiene, methylethylhexadiene, dimethylheptadiene, and the like.
Of these, cyclodecane, undecane, decane, cyclooctane, and nonane are preferable.

  Examples of the aromatic hydrocarbon of the poor solvent C include toluene, ethylbenzene, p-xylene, m-xylene, o-xylene, propylbenzene, 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, 1 2,3-trimethylbenzene, diethylbenzene, butylbenzene, triethylbenzene, styrene and the like.

  Two or more poor solvents can be used, but in this case, a substance having a boiling point higher than that of the solvent A is not included, and a substance having a boiling point higher than that of the solvent B needs to be included.

There are also preferable examples of the volume fraction in the developer of the good solvents A and B and the poor solvent C.
The volume fraction of the solvent A is preferably 5% or more and 10% or less. Since the solvent A has a high boiling point, it has a role of adjusting the shape of the resist pattern until the end of the drying process. If the volume fraction is 5% or more, the effect can be sufficiently exhibited. Moreover, if it is 10% or less, generation | occurrence | production of the swelling with respect to a resist pattern is fully suppressed.
The volume fraction of the solvent C is preferably 30% or more. This is because the occurrence of swelling with respect to the resist pattern is sufficiently suppressed. If the solvent C, which is a poor solvent, is 30% or more, since the developer is prevented from penetrating into the exposed portion of the resist pattern during development, the swelling of the resist pattern is more effectively suppressed. Further, the volume fraction of the solvent C is more preferably 50% or more. This is because it is more reliably suppressed that the developing solution penetrates into the exposed portion of the resist pattern during development, so that swelling of the resist pattern is particularly effectively suppressed.

1-E) Etching Step A resist pattern can be formed through the above steps. Using the resist pattern, a predetermined pattern is formed on the thin film 11 under the resist pattern. As shown in FIG. 1D, the thin film 11 is etched using the resist film 12 on which a predetermined resist pattern is formed as a mask. A predetermined transfer pattern is formed on the thin film 11 by etching.

  Note that a known method may be used as the etching method. A preferable example is dry etching using a reactive gas as an etchant in the step of etching the thin film 11. If the resist pattern of this embodiment is used, an accurate transfer pattern can be formed even if the reactive gas contains an isotropic etching gas.

  Further, the composition of the surface layer of the thin film 11 includes chromium, and on the other hand, the reactive gas can be preferably applied to an etching method using a mixed gas containing at least oxygen and chlorine.

1-F) Others As shown in FIG. 1E, the transfer mask 50 in this embodiment is manufactured by removing the resist pattern and appropriately performing other processes such as cleaning. These methods may be known ones.
In addition to the above structure, another film may be provided as appropriate. For example, a resist base film may be provided between the thin film 11 and the resist film 12.

<2. Advantages of the embodiment>
According to this embodiment, the following effects can be obtained.

  In addition to “good solvent with low boiling point” and “poor solvent with high boiling point”, “good solvent with higher boiling point” is added as a component of the developer so that the good solvent on the resist pattern until the final stage in the drying process. The resist pattern can be prevented from being rapidly depressed while the soluble portion of the negative resist film 12 is sufficiently dissolved. As a result, as shown in FIG. 3A (described later in the embodiment), it is possible to suppress the occurrence of distortion at the convex portion of the resist pattern and to form a linear resist pattern in plan view. Become. In addition, resist pattern swelling and pattern collapse can also be suppressed.

  As described above, according to the present embodiment, it is possible to provide a technique for forming a resist pattern having a linear pattern edge by reducing swelling of the resist pattern, pattern collapse, and distortion of the resist pattern.

Next, an Example is shown and this invention is demonstrated concretely. Of course, the present invention is not limited to the following examples.
In the following examples, the developing solution was composed of good solvents A and B and poor solvent C, whereas in the comparative example, only good solvent A, good solvent B and poor solvent C, or good solvent. A and poor solvent C.

<Examples 1-7>
1-A) Substrate with Thin Film (Mask Blank) Preparation Step 1-A-a) Substrate Preparation Step Translucent made of synthetic quartz glass having a main surface dimension of about 152 mm × about 152 mm and a thickness of about 6.25 mm The board | substrate 10 (henceforth the translucent board | substrate 10) which has was prepared.

1-Ab) Thin Film Formation Step First, a light shielding film was formed on the translucent substrate 10.
Using a single-wafer sputtering apparatus on a substrate 10 made of synthetic quartz glass, using a mixed target of molybdenum (Mo) and silicon (Si) (atomic% ratio Mo: Si = 13: 87) as a sputtering target, A MoSiN film (lower layer (light-shielding layer)) with a film thickness of 47 nm was formed by reactive sputtering (DC sputtering) in a mixed gas atmosphere of argon and nitrogen.
Subsequently, using a Mo / Si target (atomic% ratio Mo: Si = 13: 87), a MoSiN film (upper layer (surface antireflection layer)) with a film thickness of 13 nm is formed in a mixed gas atmosphere of argon and nitrogen. By doing so, the lower layer (film composition ratio Mo: 9.9 atomic%, Si: 66.1 atomic%, N: 24.0 atomic%) and the upper layer (film composition ratio Mo: 7.5 atomic%, Si: 50) A light shielding film 2 (total film thickness 60 nm) for ArF excimer laser (wavelength 193 nm) made of a laminate of 0.5 atomic% and N: 42.0 atomic%) was formed. Note that Rutherford backscattering analysis was used for elemental analysis of each layer of the light shielding film.

Next, an etching mask film was formed on the light shielding film.
The substrate 10 provided with the light shielding film was subjected to a heat treatment (annealing process) at 450 ° C. for 30 minutes to reduce the film stress of the light shielding film.
Then, an etching mask film was formed on the upper surface of the light shielding film. Specifically, in a single wafer sputtering apparatus, a CrN film (film composition ratio Cr: 75.3) is formed by reactive sputtering (DC sputtering) in a mixed gas atmosphere of argon and nitrogen using a chromium (Cr) target. (Atomic%, N: 24.7 atomic%) was formed to a thickness of 5 nm. Further, by annealing the etching mask film (CrN film) at a temperature lower than the annealing treatment of the light shielding film, the stress of the etching mask film is reduced as much as possible without affecting the film stress of the light shielding film (preferably film stress). Was adjusted to substantially zero). The binary mask substrate 10 with the thin film 11 was obtained by the above procedure.

1-B) Resist film forming step On the surface of the thin film 11 on the binary mask substrate 10, a chemically amplified negative resist composition (manufactured by Fuji Film Electronics Materials Co., Ltd.) whose base polymer is a PHS (polyhydroxystyrene) polymer. "SLV-12M negative resist") was applied by spin coating. Thereafter, the resist film 12 (thickness: 100 nm) was formed by heating at 130 ° C. for 600 seconds.

1-C) Exposure Step Next, a pattern was drawn on the resist film 12 using an electron beam drawing apparatus manufactured by Elionix. In addition, as the pattern, for example, the resist pattern was exposed so that the convex portion (line) width was 200 nm and the ratio of the line to the space was 1: 1. After drawing, the film was heated at 130 ° C. for 600 seconds.

1-D) Development Step Subsequently, in each of Examples 1 to 7, development was performed using an organic solvent. The development was performed by supplying the developer to the substrate 10 at 5 mL / second. Table 1 shows the components of the developer used in each example and the development time. In Example 2, since the unexposed portion of the resist film 12 could not be completely dissolved by one development, the development was performed twice.

  Then, drying rotation for 60 seconds was performed at high speed rotation, and it was made to dry naturally. In addition, the process after the removal of a resist pattern was not performed.

<Comparative Examples 1-3>
In Comparative Example 1, only the good solvent A was used as the developer. In Comparative Example 2, the developer was composed of only good solvent B and poor solvent C. In Comparative Example 3, the composition of the developer was only solvent A and solvent C. Other than that, it was the same as the example.

<Evaluation>
(Contrast evaluation)
About the mask blank 5 in which the resist film 12 of Examples 1-2 and the comparative example 1 was formed, the film reduction rate with respect to exposure intensity | strength (DOSE amount) was measured. The results are shown in FIG. FIG. 2 is a graph showing the results when the horizontal axis represents the exposure intensity (DOSE amount) and the vertical axis represents the remaining film ratio in this example.
In Examples 1 and 2, the change in the remaining film amount with respect to the DOSE amount was a curve similar to the tan curve, whereas in Comparative Example 1 in which only PGMEA, which is a good solvent, was used as the developer, the DOSE amount was 15 The behavior became irregular in the range of ˜18 μC / cm ² . From this, it was found that when the developer is a good solvent, contrast stability cannot be obtained.

In FIG. 2, the behavior of the curve of Comparative Example 1 is irregular when the DOSE amount is in the range of 15 to 18 μC / cm ² . The inventor has confirmed that this is not a measurement error. For example, when a sample having a residual film ratio of zero in the curve of Comparative Example 1 (DOSE amount is about 16 μC / cm ² ) was observed with an electron microscope, the resist pattern was lost. In the comparative example 1, the present inventor is intensively studying about the mechanism that causes such a phenomenon. In any case, in Examples 1 and 2, such a phenomenon does not occur and the resist pattern can be stably formed.

(Resist residue evaluation)
About the resist blank mask 1 after resist development of Examples 1-7 and Comparative Examples 1-3, the resist residue (resist reprecipitation) after development was evaluated. The evaluation was performed by irradiating the mask blank 1 with resist with a halogen lamp from the oblique direction, and visually evaluating the presence or absence of resist residue from the light reflection state. Specifically, when coarse irregular reflection was confirmed due to precipitation of fine-particle resist residue, it was judged as unacceptable (x), and when coarse irregular reflection was not confirmed, it was judged as acceptable (◯).
As a result, irregular reflection was not confirmed in Examples 1-3, 5-7, and Comparative Examples 1 and 3. In Example 4, slight fogging was confirmed in part. In Comparative Example 2, irregular reflection was confirmed. The reasoning for the reason is described below.

  In Comparative Example 2, in the drying process after development, the developer from the good solvent having the ability to dissolve the resist is volatilized out of the developer on the mask blank 5 after the resist pattern is formed. For this reason, as the drying progresses, the proportion of the poor solvent increases, and fine resist components are deposited in the developing solution in which the poor solvent is excessive. If fine particles resulting from the deposition of the resist adhere to the surface of the resist pattern or are sandwiched between spaces, they remain as resist residues without being discharged out of the substrate. The coarse irregular reflection generated in Comparative Example 2 is considered to be caused by the resist residue generated in this way.

In Examples 1 to 3 and 5 to 7, in the drying step after development, a good solvent is present throughout the developer on the mask blank 5 after forming the resist pattern. This is because the good solvent A having a boiling point higher than that of the poor solvent exists. It is considered that the efficiency of discharging the resist component to the outside of the substrate is maintained by the presence of the good solvent for the resist throughout the developer. Even when the proportion of the good solvent contained in the developer decreases with the volatilization of the good solvent B and the resist components are temporarily precipitated, the good solvent A is redissolved again with the good solvent A at the end of drying. Therefore, it is considered that the discharge efficiency of the resist component to the outside of the substrate is secured.
Further, in Example 4, since the component of the good solvent A having a high boiling point was too small, the resist component was saturated in the developing solution at the end of drying, and it was considered that the residue was slightly precipitated. .

  In Comparative Example 1, it is considered that the resist component did not precipitate in the drying process because the developer was composed entirely of a good solvent. In Comparative Example 3, since the boiling point of the good solvent is higher than the boiling point of the poor solvent, the good solvent was present even at the end of drying, so that it is considered that the resist component did not precipitate.

(Resolution evaluation)
About Examples 1-7 and Comparative Examples 1-3, the resolution was evaluated. Regarding the resolution, the critical dimension at which lines and spaces could be resolved by exposure and development was examined. In addition, there is no significant residue in the portion that is originally a resist dissolving portion, there is no sticking between adjacent resist undissolved portions, and there is no curve or meandering of a pattern greatly deviating from a predetermined drawing pattern portion, and Measure the line width of the resist undissolved portion where the width ratio of the exposed portion (resist undissolved portion) drawn with electron beam and the unexposed portion (resist melted portion) not drawn with electron beam is a predetermined value, This line width was determined as the resolution that would be a limit in practical use. Moreover, the exposure amount when the resolution which becomes the limit in practical use was obtained was determined as the necessary exposure amount. The results are shown in Table 2.
As shown in Table 2, in Comparative Example 1, which was developed with a good solvent developer, the pattern collapsed when the line width was less than 200 nm. In Comparative Example 3, the pattern collapsed when the line width was less than 120 nm. In Comparative Example 3, the volume fraction of the good solvent A in the developer is always 50% or more, and the concentration of the solvent A gradually increases toward the end of drying, so that the initial swelling state of the resist pattern is maintained. Therefore, it is considered that the resolution is low.
On the other hand, in Examples 1-7 and Comparative Example 2 in which a good solvent and a poor solvent were mixed, it was found that the resolution was excellent. In Example 5, the resolution was slightly lower than that of other developing solutions, but this is considered to be due to the fact that the proportion of the solvent C was small.

(Evaluation of line edge roughness)
In order to evaluate the line edge roughness (LER) in Examples 1 to 4, 6, 7 and Comparative Example 2 at a line width of 80 nm, an enlarged view of the resist pattern was taken with an electron micrograph. The result is shown in FIG. In addition, the numerical value of LER was measured using CD-SEM made from Advantest Corporation. In Example 5, the line edge roughness (LER) at a line width of 90 nm was evaluated.
3A is an SEM image of Example 1, and FIG. 3B is an SEM image of Comparative Example 2. In Example 1, the edge portion was linear. That is, no distortion occurred when the resist pattern was viewed in plan. The LER value of the resist pattern was 5.53 nm. The difference between the maximum line width and the minimum line width of the convex portion of the resist pattern was 7.01 nm. For other Examples 2 to 7, the LER value of the resist pattern was less than 6.0 nm. Further, the difference between the maximum and minimum line widths of the convex portions of the resist patterns of Examples 2 to 7 was less than 7.5 nm.
On the other hand, as shown in FIG. 3B, in Comparative Example 2, the edge portion was a gentle wavy line. In addition, as in a portion surrounded by a broken-line circle, a significant dent was generated in the convex portion of the resist pattern when viewed in plan. That is, distortion occurred when the resist pattern was viewed in plan. The LER value of the resist pattern was 6.32 nm. The difference between the maximum line width and the minimum line width of the convex portion of the resist pattern was 8.65 nm.

<Production of transfer mask>
Using the resist patterns formed in Examples 1 to 3 and Comparative Examples 1 and 2 as a mask, the thin film 11 was etched to form a concavo-convex pattern on the thin film 11 to produce a transfer mask 50.
First, dry etching was performed on an etching mask film made of a CrN film using the resist pattern as a mask to form an uneven pattern on the etching mask film. As a dry etching gas, a mixed gas of oxygen and chlorine (O ₂ : Cl ₂ = 1: 4) was used.
Next, the remaining resist pattern was removed by ashing or the like, and then the light shielding film was dry-etched using the concave / convex pattern formed on the etching mask film as a mask to form a light shielding film pattern. As the dry etching gas, a mixed gas of SF ₆ and He was used.
Finally, the etching mask film pattern was removed using a mixed gas of oxygen and chlorine (O ₂ : Cl ₂ = 1: 4).
A transfer mask 50 was obtained as described above.

<Evaluation of transfer mask>
Next, using the obtained binary transfer mask 50, a process of exposing and transferring the transfer pattern to the resist film on the semiconductor wafer, which is a transfer target, was performed. As the exposure apparatus, an immersion type exposure apparatus using an ArF excimer laser as a light source was used.
The resist film on the exposed semiconductor wafer was subjected to a predetermined development process to form a resist pattern. Then. A circuit pattern including a line and space (L & S) pattern having a DRAM half pitch (hp) of 40 nm was formed on a semiconductor wafer.
When the circuit pattern on the obtained semiconductor wafer was confirmed with an electron microscope (TEM), the circuit pattern formed using the transfer mask 50 obtained in Examples 1 to 3 described above was DRAM half pitch ( hp) 40 nm line and space pattern specifications were fully met.

On the other hand, the circuit pattern formed using the transfer mask 50 obtained in Comparative Example 1 has many short-circuited portions and disconnected portions in the line and space pattern portion, and DRAM half pitch (hp) The specification of 40 nm could not be satisfied.
Further, although the transfer mask 50 obtained in Comparative Example 2 satisfies the specification of a line and space pattern with a DRAM half pitch (hp) of 40 nm, a portion where the line width is narrow is generated. It is considered difficult to cope with a specification with a half pitch (hp) of less than 40 nm.

From the above results, compared to the comparative example, this example was able to reduce resist pattern swelling, pattern collapse, and resist pattern distortion, and to form a resist pattern having linear pattern edges.
In addition, it was found that in this example, a transfer mask having an excellent mask pattern can be obtained by using a resist pattern having an excellent pattern shape as a mask.

1 ... Mask blank with resist 5 ... Mask blank 10 ... Substrate 11 ... Thin film 12 ... Resist film 50 ... Transfer mask

Claims (11)

A method for manufacturing a transfer mask,
Preparing a substrate having a thin film;
Forming a resist film on the surface of the thin film;
Exposing the resist film;
Forming a resist pattern by performing a process of developing the resist film after exposure; and
Etching the thin film using the resist pattern as a mask;
Is included,
In the step of forming the resist pattern,
The resist film is a resist film formed with a chemically amplified and negative resist solution,
The developing solution used when performing the developing step is solvent A and solvent B which are organic solvents, and solvent C which is an organic solvent and hardly dissolves the resist film as compared with the solvent A and the solvent B. And the boiling point of the solvent A is higher than that of the solvent C, and the boiling point of the solvent C is higher than that of the solvent B. The dissolution rate of the solvent A and the solvent B in the resist film is 10 nm / sec or more at 23 ° C.,
2. The method for producing a transfer mask according to claim 1, wherein a dissolution rate of the solvent C in the resist film is 0.5 nm / sec or less at 23 ° C. 3.   3. The method for producing a transfer mask according to claim 1, wherein the solvent B has a faster dissolution rate in the resist film than the solvent A. 4.   The method for manufacturing a transfer mask according to claim 1, wherein a volume fraction of the solvent A in the developer is 5% or more and 10% or less.   5. The method for producing a transfer mask according to claim 1, wherein the boiling point of the solvent A is 140 ° C. or higher and 250 ° C. or lower.   6. The transfer mask according to claim 1, wherein at least one of the solvent A and the solvent B is the same as at least one of the solvents constituting the resist solution. Manufacturing method.   The method for manufacturing a transfer mask according to claim 1, wherein a volume fraction of the solvent C in the developer is 30% or more.   The method for manufacturing a transfer mask according to claim 1, wherein a volume fraction of the solvent C in the developer is 50% or more.   9. The method according to claim 1, wherein in the step of etching the thin film, dry etching using a reactive gas as an etchant is performed, and the reactive gas includes an isotropic etching gas. A method for producing the transfer mask according to claim.   10. The method for manufacturing a transfer mask according to claim 9, wherein chromium is contained in a composition of a surface layer of the thin film, and the reactive gas is a mixed gas containing at least oxygen and chlorine. A developer used when performing a development process in accordance with forming a resist pattern from a resist film formed by a chemically amplified and negative resist solution,
The developer contains an organic solvent, solvent A and solvent B, and an organic solvent, which is a solvent C that is less soluble in the resist film than the solvent A and the solvent B.
A developing solution, wherein the boiling point of the solvent A is higher than that of the solvent C, and the boiling point of the solvent C is higher than that of the solvent B.