JP4822239B2 - Mask blank, method for manufacturing the same, and method for manufacturing the mask - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, the resist function is manifested by reacting, as a resist species, an acid of a catalyst substance generated in a resist film by exposure with a functional group or a functional substance that controls the solubility of the polymer in a subsequent heat treatment step. The present invention relates to a mask blank using a chemically amplified resist, a manufacturing method thereof, a mask manufacturing method, and the like.
[0002]
[Prior art]
In the manufacture of a photomask (reticle) used in a microfabrication technique that is a manufacturing method of a semiconductor device or the like (LSI or the like), for example, a chromium film as a light shielding layer is formed on a transparent substrate, and an antireflection layer is formed on the chromium film. A photomask blank prepared by forming a certain chromium oxide film and forming a resist film on the chromium oxide film is prepared in advance. In this photomask blank, selective exposure of the resist is performed, and a resist pattern is formed through post-exposure baking and development, and the chromium oxide film and the chromium film are selectively etched using the resist pattern as a mask. The photomask is manufactured by removing and forming a predetermined mask pattern.
Further, in the manufacture of a halftone phase shift mask used in recent ultra-fine processing technology, for example, a chromium oxide film or a chromium fluoride film or an oxidation and / or oxidation film having both a light shielding function and a phase shift function on a transparent substrate. A phase shift mask blank prepared by forming a half-tone film of a molybdenum nitride silicide film and forming a resist film on the half-tone film is prepared in advance. Then, in this phase shift mask blank, the resist is selectively exposed, a resist pattern is formed through post-exposure baking and development, and both the light shielding function and the phase shift function are performed using this resist pattern as a mask. The phase shift mask is manufactured by selectively removing the provided halftone film by etching to form a predetermined mask pattern.
[0003]
In the mask manufacturing field described above, the acceleration voltage of an electron beam in resist drawing (exposure) using an electron beam is about to shift from the current 10 to 20 keV to 50 keV or more. This is because it is necessary to resolve a finer resist pattern by reducing the forward scattering of the electron beam passing through the electron beam resist and increasing the focusing property of the electron beam. When the acceleration voltage of the electron beam is low, forward scattering occurs on the resist surface or in the resist, and when there is forward scattering, the resolution of the resist deteriorates.
However, when the acceleration voltage of the electron beam is set to 50 keV or more, forward scattering decreases in inverse proportion to the acceleration voltage and energy applied to the resist by forward scattering decreases. Therefore, the electron beam used at 10 to 20 keV Resist lacks the sensitivity of the resist, resulting in a decrease in throughput. Therefore, in the mask manufacturing field, it has become necessary to use a chemically amplified resist having high sensitivity to high acceleration voltage and high resolution.
[0004]
[Problems to be solved by the invention]
A photomask blank and a method for manufacturing the photomask will be described in detail with reference to FIG.
First, a chromium film 2 as a light shielding film and a chromium oxide film 3 as an antireflection film are formed intermittently or continuously on the surface of a transparent substrate 1 such as synthetic quartz by a sputtering method or the like. Next, on the chromium oxide film 3, “the acid of the catalyst substance produced in the resist film by exposure reacts with a functional group or a functional substance that controls the solubility of the polymer in the subsequent heat treatment step, thereby causing the resist function. A “chemically amplified resist” that is expressed (becomes dissolved in alkali by removing functional groups, etc.) is applied by a spin coating method or the like, then heat treated (baked) and dried to form a chemically amplified resist film 4. Then, mask blanks 5 are obtained (FIG. 1A).
Next, a predetermined portion is selectively irradiated with light or an electron beam, and then the blanks 5 (that is, the chemically amplified resist film 4) is baked, and then the chemically amplified resist film 4 is developed and exposed. The resist pattern 4a is formed by removing the part (FIG. 1B).
Next, the exposed chromium oxide film 3 and the chromium film 2 are removed by a wet etching process using an etching solution (for example, a ceric ammonium nitrate chromium etching solution) or a dry etching process using an etching gas (for example, chlorine gas). Thereafter, the resist pattern 4a is removed to obtain a photomask 6 (FIG. 1C).
In the development process, as shown in FIG. 2A, there is a problem that a footing-like protrusion 7 is generated at the bottom of the chemically amplified resist film 4 (resist film near the chromium oxide film). . Such a skirt-like protrusion 7 is an unnecessary residue of the exposed portion 8 that should be completely removed by the development process, and the edge portions of the pattern formed on the chromium oxide film 3 and the chromium film 2 are notched. 2 and the pattern dimension uniformity is significantly impaired, or in some cases, as shown in FIG. 2B, adjacent resist patterns are connected to each other at a part or all of the resist bottom 9 to form the chromium oxide film 3. In addition, the chrome film 2 is not etched at all, resulting in poor resolution or degraded resolution.
[0005]
The present invention has been made to solve the above-described problems, and in mask blanks coated with a chemically amplified resist, the occurrence of tail-like protrusions that occur at the bottom of the pattern after formation of the resist pattern, etc. An object of the present invention is to provide mask blanks that can be suppressed, a method for manufacturing the same, a method for manufacturing a mask, and the like.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has the following configuration.
[0007]
(Configuration 1) A light shielding film is formed on a transparent substrate, a chemically amplified resist film is formed on the light shielding film, a resist pattern is formed by patterning the chemically amplified resist film, and the resist pattern is formed. In a mask blank used for manufacturing a mask comprising selectively etching and removing the light-shielding film as a mask,
A substance having an action of removing an acid or a functional group in an amount that does not cause the tailing of the chemically amplified resist exists at least near the surface of the light shielding film on the side where the chemically amplified resist film is formed. Characteristic mask blank.
[0008]
(Structure 2) The mask blank according to Structure 1, wherein an acid containing sulfuric acid is present at least near the surface of the light-shielding film on the side where the chemically amplified resist film is formed.
[0009]
(Structure 3) having a process of interposing a substance having an action of removing an acid or a functional group in an amount that does not cause the bottom of the chemically amplified resist on the surface of the film to which the chemically amplified resist is applied. A method for producing a mask blank characterized by the above.
[0010]
(Configuration 4) A light shielding film is formed on a transparent substrate, a chemically amplified resist film is formed on the light shielding film, a resist pattern is formed by patterning the resist film, and the resist pattern is used as a mask. In the manufacturing method of a mask blank used for manufacturing a mask consisting of selectively removing a light-shielding film by etching,
After forming the light-shielding film, at least the surface of the light-shielding film is acid-treated so that acid is present at least near the surface on the side where the chemically amplified resist film is formed. A method for manufacturing a mask blank.
[0011]
(Structure 5) The mask blank according to Structure 4, wherein the acid treatment is performed by any one of immersion in a solution containing an acid, contact of the solution containing the acid, and exposure to an atmosphere containing the acid. Manufacturing method.
[0012]
(Structure 6) Structure 4 characterized in that after the acid treatment, a rinse treatment is performed to adjust the amount of acid present at least near the surface of the light-shielding film on the side where the chemically amplified resist film is formed. Or the manufacturing method of the mask blank of 5.
[0013]
(Structure 7) The mask blank manufacturing method according to any one of Structures 4 to 6, wherein the acid is an acid containing sulfuric acid.
[0014]
(Structure 8) A mask manufacturing method comprising forming a light-shielding film pattern by patterning a light-shielding film in a mask blank obtained by the method according to any one of Structures 4 to 7.
[0015]
The mask blank referred to in the present invention includes a photomask blank and a phase shift mask blank. The mask blank referred to in the present invention includes a blank with a resist film and a blank before forming a resist film. The phase shift mask blank referred to in the present invention includes a case where a light shielding film such as a chromium-based material is formed on a halftone film.
The mask referred to in the present invention includes a photomask and a phase shift mask.
The mask referred to in the present invention includes a reticle.
[0016]
Hereinafter, the present invention will be described in detail.
The following mechanisms can be considered as the cause of the above problems.
As described above, the function of the chemically amplified resist (positive type) is that the acid of the catalyst substance produced in the resist film by exposure is a functional group or functional substance that controls the solubility of the polymer in the subsequent heat treatment step. The resist function is expressed by reacting with (the exposed part is dissolved in an alkali developer by removing the functional group or the like). Therefore, the concentration of the acid of the catalyst substance produced in the resist film by exposure is remarkably lowered for some reason (generally called deactivation), and is not dissolved in the alkali developer. This phenomenon occurs in the vicinity of a film to which a chemically amplified resist is applied (hereinafter simply referred to as a base film), for example, in the vicinity of a chromium-based light-shielding film (that is, at the bottom of the resist film). it is conceivable that.
The above deactivation phenomenon is caused by the fact that the acid of the catalyst substance generated in the resist film by exposure moves by diffusion into the base film (for example, a chromium-based light-shielding film), or on the surface of the base film or in the vicinity of the surface. This may be caused by the presence of an alkaline substance in the upper layer or the underlying film exhibiting alkalinity.
Then, as in the invention described in the above configuration 1, an amount of acid that does not cause tailing of the chemically amplified resist at least near the surface of the mask blank on the side where the chemically amplified resist film is formed, Alternatively, a mask blank that can prevent or suppress the occurrence of tailing can be obtained by the presence of a substance that has an effect of removing a functional group.
This is because the acid near the surface of the light-shielding film on the side where the chemically amplified resist film is formed is in an acid-rich state, so that the acid of the catalyst substance produced in the resist film by exposure is chemically amplified. It becomes difficult to move in the film (undercoat film) to which the resist is applied by diffusion, or the alkaline substance existing on the surface of the undercoat film or in the upper layer in the vicinity of the surface is removed, or it is acidic to the undercoat film exhibiting alkalinity. It is considered that the deactivation phenomenon can be avoided by performing the process of presenting.
In addition, the acid in the structure 1 should just be what can prevent or suppress generation | occurrence | production of the bottoming of a chemically amplified resist. The substance having the action of removing the functional group or the like may be any substance that includes a substance that acts to remove the functional group by reacting with the functional group or the functional substance that controls the solubility of the chemically amplified resist.
In the present invention, the “light-shielding film” includes a light-shielding film that blocks exposure light, and a halftone film having a light-shielding function and a phase shift function.
The film material, film composition, film structure, film thickness, etc. of the light-shielding film are not particularly limited.
As a film material of the light-shielding film, for example, chromium alone, a material containing at least one element composed of oxygen, nitrogen, or carbon in chromium, or an acetal resist or HEAR (for LEAR (Low Energy Activation Resist)) is used. For example, when a chemically amplified resist such as an SCAP resist is used for high energy activation resist, a film material in which a trailing protrusion is formed on the bottom of the resist pattern may be used.
Here, the acid may be any acid that does not cause tailing or has an effect of significantly reducing tailing, and examples thereof include inorganic acids such as sulfuric acid and organic acids. To these acids, an oxidizing agent such as hydrogen peroxide solution or ozone-dissolved water can be added.
In addition, as in the invention described in the above configuration 2, an acid containing sulfuric acid is preferable among the acids because it tends to remain in the base film or on the surface thereof.
[0017]
Further, as in the invention described in the above configuration 3, a substance that acts to remove an acid or a functional group in an amount that does not cause tailing of the chemically amplified resist on the surface of the film to which the chemically amplified resist is applied. It was found that the occurrence of tailing can be prevented or suppressed by performing the intervening process. In other words, the shape of the tail changes depending on the amount of acid remaining and the acid deposition (trapping) state on the surface of the film to which the chemically amplified resist is applied, and the amount of acid remaining and acid deposition (trapping) state are changed. It was found that the occurrence of tailing can be prevented or suppressed by controlling.
This is because, by keeping the surface of the film on which the chemically amplified resist film is formed in an acid-rich state, the acid of the catalytic substance generated in the resist film by exposure is applied to the chemically amplified resist. It becomes difficult to move in the film (underlying film) due to diffusion, or the alkaline substance existing on the surface of the undercoating film or in the upper layer in the vicinity of the surface is removed, or the underlying film that has been alkaline is treated to be acidic. Therefore, it is considered that the deactivation phenomenon can be avoided.
[0018]
Further, as in the invention described in the above configuration 4, after the light shielding film is formed, at least the light shielding is performed so that the acid is present at least near the surface of the light shielding film on the side where the chemically amplified resist film is formed. It was found that by acid treatment of the surface of the conductive film, the deactivation of the chemically amplified resist film can be suppressed very effectively as in the examples described later, and the occurrence of tail-like protrusions can be suppressed. .
[0019]
In addition, as in the invention described in the fifth aspect, the acid treatment is any one of a method of immersing in an acid-containing solution, a method of contacting an acid-containing solution, and a method of exposing to an acid-containing atmosphere. Do one. In particular, acid bath dipping treatment in an acid-containing solution controls chemical amplification of the light-shielding film by controlling conditions such as concentration, temperature, dipping time, rinsing time after acid bath dipping treatment, and the presence or absence of ultrasonic waves. This is preferable because the amount of acid present at least in the vicinity of the surface on the side where the mold resist film is formed can be strictly controlled.
[0020]
In addition, as in the invention described in the configuration 6, after the acid treatment, the rinsing treatment is performed from the viewpoint of easy control of the amount of acid present at least near the surface of the light-shielding film on the side where the chemically amplified resist film is formed. It is preferable to adjust the amount of acid present near the surface of the light-shielding film on the side where the chemically amplified resist film is formed.
[0021]
In addition, as in the invention described in the seventh aspect, among acids, an acid containing sulfuric acid is preferable because it easily remains in the base film or on the surface thereof. If an acid solution containing sulfuric acid widely used in mask cleaning (for example, hydrogen peroxide is added to concentrated sulfuric acid) is used, cleaning treatment for the light-shielding film, which is the base film, and tailing are performed. It is preferable from the simplification of the process that can simultaneously achieve the acid treatment that does not cause or controls.
[0022]
Further, when a mask (reticle) is produced by using an acid-treated mask blank as in the invention described in Structure 8, tail-like projections generated at the bottom of the resist pattern after the development of the chemically amplified resist are effective. Can be suppressed. Therefore, even if the pattern edge is jagged due to the occurrence of protrusions, which has been a problem, and the pattern is extremely fine, there is almost no resolution failure due to short-circuiting or connection of protrusions. Improves.
[0023]
Example 1
On a synthetic quartz substrate having a size of 6 inches square and a thickness of 0.25 inches, a light-shielding film mainly composed of chromium having a thickness of about 600 angstroms is formed by sputtering, followed by oxidation of about 300 angstroms in thickness. An antireflection film mainly composed of chromium was formed.
The obtained substrate is immersed in an acid bath heated to about 120 ° C. with 98% concentrated sulfuric acid for about 5 minutes, and then rinsed with warm pure water (rinsing so that the bottom of the chemically amplified resist used does not occur or is minimized) The time was set) and dried by a spin dry method. When the film surface of the substrate subjected to the acid bath immersion treatment was analyzed by secondary ion mass spectrometry (SIMS), it was confirmed that S (sulfur) was present. From this result, it is considered that sulfuric acid was impregnated or trapped in the vicinity of the surface of the light-shielding film by the acid bath immersion treatment.
Next, a commercially available chemically amplified positive resist for electron beam exposure (OEBR-CAP209: manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied to a thickness of 400 nm by a spin coating method on the substrate subjected to the acid bath immersion treatment, and then 130 by a hot plate. The resist film was dried at 10 ° C. for 10 minutes to obtain a photomask blank with a resist film.
Next, this mask blank was exposed with an electron beam exposure apparatus, and then a post-exposure baking process was performed, followed by a development process to form a resist pattern.
Next, the light-shielding films (chromium oxide film and chromium film) exposed with a chromium etching solution, which is a solution of cerium diammonium nitrate and perchloric acid, were removed by etching. Finally, the resist pattern was immersed in a resist stripping solution obtained by adding hydrogen peroxide to concentrated sulfuric acid, and the resist pattern was removed to obtain a photomask (reticle).
When the protruding portion (pattern edge with knurls) of the light-shielding film (chromium oxide film and chrome film) pattern in the obtained photomask was examined with SEM (scanning electron microscope), it was found to have a knurl of about 10 nm. . Further, it was confirmed that a 100 nm line & space pattern was resolved.
[0024]
Comparative Example 1
In Example 1 above, a photomask blank and a photomask were produced in the same manner as Example 1 except that the acid bath immersion treatment was not performed.
A mask blank produced without applying an acid bath immersion treatment when the projections (with pattern edge knurls) of the light-shielding film (chromium oxide film and chromium film) pattern of the obtained photomask are examined with an SEM (electron microscope). In this case, the roughness was about 30 nm, and the 200 nm line & space pattern was only resolved. That is, the space between the resist patterns for preventing a defective resolution because a part of the bottom of the resist pattern is not connected is 200 nm at the minimum.
This is because there is a microporus near the surface of the antireflection film, and the acid of the catalyst substance generated in the resist film by exposure moves to the vicinity of the surface of the antireflection film and impregnates the microporus. By being captured, the skirt portion of the resist pattern to be formed is deactivated and a skirt-like protrusion is generated, which is considered to be the above result.
[0025]
Example 2
A chromium oxide halftone film having a thickness of about 800 angstroms was formed on a synthetic quartz substrate having a size of 6 inches square and a thickness of 0.25 inches by sputtering.
The obtained substrate is immersed in an acid bath heated to about 120 ° C. with 98% concentrated sulfuric acid for about 5 minutes, and then rinsed with warm pure water (rinsing so that the bottom of the chemically amplified resist used does not occur or is minimized) The time was set) and dried by a spin dry method. When the film surface of this acid bath immersion-treated substrate was analyzed by secondary ion mass spectrometry (SIMS), it was confirmed that sulfur (S) was present. From this result, it is considered that sulfuric acid was impregnated or captured in the vicinity of the surface of the membrane by the acid bath immersion treatment.
Next, a commercially available chemically amplified positive resist for electron beam exposure (OEBR-CAP209: manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied to a thickness of 400 nm by a spin coating method on the substrate subjected to the acid bath immersion treatment, and then 130 by a hot plate. The resist film was dried at 10 ° C. for 10 minutes to obtain a phase shift mask blank with a resist film.
Next, this phase shift mask blank was exposed with an electron beam exposure apparatus, and then a post-exposure baking process was performed, followed by a development process to form a resist pattern.
Next, the chromium oxide film exposed with a chromium etching solution which is a solution of ceric ammonium nitrate and perchloric acid was removed by etching. Finally, the resist pattern was immersed in a resist stripping solution obtained by adding hydrogen peroxide to concentrated sulfuric acid, and the resist pattern was removed to obtain a phase shift mask (reticle).
When the protrusion (pattern edge jaggedness) of the halftone film (chromium oxide film) pattern in the obtained phase shift mask was examined with a SEM (scanning electron microscope), it was found to have a jaggedness of about 10 nm. Further, it was confirmed that a 100 nm line & space pattern was resolved.
[0026]
In addition, this invention is not limited to the Example etc. which were mentioned above.
For example, the material of the light-shielding film in the photomask and the halftone film in the phase shift mask may be a film that generates a skirt-like protrusion at the bottom (hem part) of the resist pattern when the acid bath immersion treatment is not applied. For example, the acid bath immersion treatment of the present invention can be applied.
Further, the type of the chemically amplified resist is not limited, and the same effect as in the above-described embodiment was also observed when another chemically amplified resist (for example, FEP171: manufactured by Fuji Film Arch) was used. The chemically amplified resist may be a negative type.
Similar trends were observed when other acids were used. The same tendency was observed when hydrogen peroxide was added to the concentrated sulfuric acid in the above-described Examples.
Also, without rinsing, set the acid treatment conditions (concentration, heating temperature, treatment time) so that tailing does not occur or is minimized in the chemically amplified resist used. You can also.
[0027]
【The invention's effect】
As described above, according to the present invention, the surface of the film to which the chemically amplified resist is applied is provided with a substance that acts to remove an acid or a functional group in an amount that does not cause the tailing of the chemically amplified resist. Thus, it is possible to suppress the occurrence of tail-like protrusions at the bottom of the chemically amplified resist pattern.
In addition, by treating the surface of a film such as a light-shielding film in a photomask blank or a halftone film in a phase shift mask blank, deactivation of a chemically amplified resist film formed on these films can be suppressed, It is possible to suppress the occurrence of skirt-like protrusions at the bottom of the resist pattern.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view for explaining a manufacturing process of a mask blank and a mask.
FIG. 2 is a schematic diagram for explaining a skirt-like protrusion at the bottom of a resist pattern.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Chromium film 3 Chromium oxide film 4 Chemical amplification type resist film 4a Resist pattern 5 Mask blank 6 Photomask 7 Footing-like protrusion 8 Originally exposed portion 9 to be removed by development processing Resist bottom

Claims (5)

A light shielding film is formed on a transparent substrate, a positive chemically amplified resist film is formed on the light shielding film, a resist pattern is formed by patterning the resist film, and the light shielding is performed using the resist pattern as a mask. In the manufacturing method of the mask blank used for manufacturing the mask, which consists of selectively etching away the conductive film,
After forming the light-shielding film, at least the surface of the light-shielding film is acid-treated so that an acid is present at least near the surface on the side where the chemically amplified resist film is formed .
After the acid treatment, a rinse with warm pure water is performed to adjust the amount of acid present at least near the surface of the light-shielding film on the side where the chemically amplified resist film is formed. Method. The acid treatment is immersed in a solution containing acid, contacting the solution containing an acid, exposing to an atmosphere containing an acid method according to claim 1, wherein the mask blank and performing any one of . The acid method according to claim 1 or 2, wherein the mask blank is characterized in that an acid containing sulfuric acid. 4. The rinsing treatment with warm pure water is performed by setting a rinsing time so that tailing does not occur in the chemically amplified resist to be used or tailing is minimized. Mask blank manufacturing method . A mask manufacturing method comprising patterning a light-shielding film in a mask blank obtained by the method according to claim 1 to form a light-shielding film pattern.

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