JP2016167092A - Photomask blank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photomask blank to be used for manufacturing a photomask, for inexpensively manufacturing a mask that is used for photolithography technology with a 65 nm half pitch and beyond, and that has a mask pattern excellent in dimensional accuracy of a minute pattern and high uniformity in an in-plane dimensional distribution.SOLUTION: The photomask blank includes at least a light-shielding film 13 formed on one major surface of a transparent substrate 11. A non-photosensitive silicon-based polymer layer 14 having a film thickness of 10 nm to 100 nm is formed on the light-shielding film, and an electron beam resist film is deposited on the silicon-based polymer layer. The silicon-based polymer layer comprises a siloxane ladder polymer or a silicon-based polymer having one structure of a trialkylsilyl structure, a trialkoxysilyl structure and a polysilane structure.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a photolithography technique used for pattern formation of a semiconductor device, and more particularly to a photomask blank used for a photolithography technique with a half pitch of 65 nm or more.

In order to realize high integration and ultra-miniaturization of recent semiconductor devices that progress from a half pitch of 65 nm to 45 nm and further to 32 nm, in photolithography, as a high resolution technique in an exposure apparatus, a high NA exposure technique, Development of exposure technology with polarized illumination, and further immersion exposure technology is rapidly progressing.
On the other hand, in order to improve the resolution of a photomask (also referred to as a reticle) used for photolithography, miniaturization and high accuracy of a conventional binary mask composed of a light transmitting portion and a light shielding portion are being promoted. At the same time, a phase shift mask such as a halftone type phase shift mask composed of a light transmitting portion and a semi-transmitting portion is being put into practical use in order to improve resolution by utilizing light interference.

A photomask for forming a semiconductor device having a fine pattern is required to have high precision along with fine pattern line width as an original, and critical dimensions such as gate pattern line width are strictly managed as CD (Critical Dimension). Therefore, the target allowable value of the pattern is set in advance.
Also, the uniformity of the in-plane distribution of CD within one photomask (Critical Dimension Uniformity: hereinafter also referred to as CDU) is important.
The definition of the CDU is various, and there are cases where the CDU is defined to include a shape in which the pitch is changed while being the same CD.
However, CD is caused by various factors such as the accuracy of a drawing device such as an electron beam drawing device used for mask pattern creation, the characteristics of a resist such as an electron beam resist, the characteristics of an object to be etched such as a light shielding film, and the etching processing accuracy. However, the CD dimension (also referred to as CDE: Critical Dimension Error) does not occur as designed.
Particularly, a CDU having a shape in which the pitch is changed has a large CDE depending on etching conditions and characteristics of a workpiece.

In a conventional photomask manufacturing method, for example, a half-tone phase shift mask blank having a two-layer structure in which a light-shielding film is formed on a halftone material film is used, an electron beam resist is applied to the blank, and a pattern is formed with an electron beam. After drawing and developing, the light shielding film and the halftone material film are sequentially dry etched to produce a mask pattern (see, for example, Patent Document 1 and Patent Document 2).
However, with this conventional method, it has already become difficult to manufacture a photomask of 45 nm node (half pitch 65 nm) or later.
As an example, a CDU including the above-mentioned density characteristics can be cited. In the conventional method, a CDU including a different pitch is required to be 4.8 nm (ITRS2005: the International Technology for Semiconductors) at 3σ. The CDU of the line width is calculated from 3σ2.6 nm and the CDE due to the pitch component is expected to be 4 nm or less, whereas the CDE due to the pitch component is about 8 nm (from 260 nm 1 to 1 to the isolated pattern), which is required. A problem has arisen that CDUs that are not within the allowable range.

In order to realize ultra-fine photomasks, it is required to improve the resolution of resists such as electron beam resists and to improve the resolution of dry etching processes such as light shielding films.
With regard to resists, high resolution and stability are required, but new resists with excellent characteristics such as resolution and stability are now being prepared for semiconductor devices with a half pitch of 45 nm. There is no prospect of practical use.
Further, with respect to dry etching apparatus and conditions, it is expected to improve uniformity and resolution and to have a high resist selectivity ratio. However, there is no prospect for practical use at present.
Therefore, development of a method for maximizing the resolution of the current resist and improving the resolution on the photomask processing side including dry etching such as a light shielding film is required.

A problem in dry etching is a decrease in etching bias in a fine pattern portion due to a difference in density between mask patterns.
The etching bias is defined as the dimensional change amount of the etching target after etching with respect to the resist pattern dimension (side etching amount).
That is, when the portion to be etched is small, a phenomenon that the etching bias becomes smaller than that of the large portion occurs, and the CDU is impaired. If this phenomenon is improved by changing the dry etching conditions, for example, if the anisotropic etching property is increased, the CDE due to the difference in density of the pattern is improved, but the dry etching resistance of the resist is a problem. Thus, there arises a problem that the resist pattern disappears during the etching.
In addition, when this method is applied, there is a problem that the CDU is lowered due to the same pitch and the same size. It is necessary to develop equipment including dry etching conditions.

In order to reinforce the dry etching resistance of the resist, it is sufficient to increase the thickness of the resist. However, when the film thickness is increased, the resolution of the resist itself after development is lowered, and the resist collapses after development. Met.
On the other hand, silicon-based electron beam resists have been proposed to increase dry etching resistance, but increasing the silicon content to increase dry etching resistance decreases the resist resolution, and there is a relationship between etching resistance and resolution. There is no prospect of practical application for technologies with a half pitch of 65 nm or more.
Currently, various resist materials are being studied, but no resist material having good characteristics such as high resolution and high dry etching resistance has been found yet.

Therefore, a method for reducing the film thickness of the light shielding film to achieve high resolution and shortening the etching time of the light shielding film has been studied.
However, in order to maintain the original optical characteristics as the light shielding film, there is a problem that it is difficult to make the light shielding film thinner than a certain thickness.

JP-A-8-101493 Japanese Patent Laid-Open No. 11-15135

Therefore, the present invention has been made in view of the above problems.
That is, it is used in a photomask manufacturing method for manufacturing a mask having a mask pattern that is used in a photolithography technique with a half pitch of 65 nm or more, has a fine pattern dimensional accuracy, and has a high uniformity of dimensional in-plane distribution at low cost. Photomask blanks are provided.

  In order to solve the above-mentioned problems, a photomask blank according to the invention of claim 1 is a photomask blank in which at least a light-shielding film is formed on one main surface of a transparent substrate, and is not on the light-shielding film. A photosensitive silicon polymer layer is formed with a film thickness ranging from 10 nm to 100 nm, an electron beam resist film is laminated on the silicon polymer layer, and the silicon polymer layer is a siloxane ladder. It is characterized by containing a polymer or a silicon-based polymer having any one of a trialkylsilyl structure, a trialkoxysilyl structure, and a polysilane structure.

  A photomask blank according to a second aspect of the present invention is the photomask blank according to the first aspect, wherein the light shielding film contains chromium.

  A photomask blank according to a third aspect of the present invention is the photomask blank according to the first or second aspect, wherein the light shielding film is laminated on a halftone material film. Is.

  A photomask blank according to a fourth aspect of the present invention is the photomask blank according to the third aspect, wherein the film thickness of the silicon-based polymer layer is smaller than the film thickness of the halftone material film. It is.

  A photomask blank according to a fifth aspect of the present invention is the photomask blank according to the third or fourth aspect, wherein the halftone material film contains a compound that can be dry-etched by a fluorine-based gas. It is.

A photomask blank according to a sixth aspect of the present invention is the photomask blank according to any one of the first to fifth aspects, wherein the electron beam resist film has a thickness in the range of 100 nm to 300 nm. It is characterized by.
The photomask blank according to claim 7 is the photomask blank according to any one of claims 1 to 6, wherein the dry etching resistance of the silicon-based polymer layer by a chlorine-based gas is It is characterized by being at least twice that of the electron beam resist film.

  A first photomask manufacturing method according to the present invention is a non-photosensitive material having a transparent substrate and at least a light-shielding film formed on one main surface of the transparent substrate, and having a high resistance to dry etching by a chlorine-based gas on the light-shielding film. A method for producing a photomask using a photomask blank in which a conductive silicon polymer layer is applied and formed, in order: (1) a step of applying and forming a thin resist film on the silicon polymer layer; (2) patterning the resist film to form a resist pattern; and (3) forming a silicon polymer pattern by dry etching the silicon polymer layer with a fluorine gas using the resist pattern as a mask. And (4) a step of stripping the resist pattern, and (5) the silicon polymer pattern as a mask. It is characterized in that it has a step of forming a light-shielding film pattern is dry-etched by chlorine-based gas the light shielding film Te.

  A second photomask manufacturing method according to the present invention is characterized in that, in the first photomask manufacturing method, the step (4) and the step (5) are interchanged.

  A third photomask manufacturing method according to the present invention is the first or second photomask manufacturing method, wherein the light shielding film is formed by being laminated on a halftone material film, and the step (1 ) To (5), in order, (6) The halftone material film is dry-etched with a fluorine-based gas using the light-shielding film pattern as a mask to form a halftone mask pattern, and at the same time, the silicon-based polymer pattern And (7) a step of removing a part or all of the light-shielding film pattern.

  A fourth photomask manufacturing method according to the present invention is characterized in that, in any of the first to third photomask manufacturing methods, the thickness of the resist film is in a range of 100 nm to 300 nm. Is.

  A fifth photomask manufacturing method according to the present invention is the photomask manufacturing method according to any one of the first to fourth photomasks, wherein the silicon-based polymer layer has a resistance to dry etching by a chlorine-based gas of 2 of the resist film. It is characterized by being more than double.

In the photomask blank of the present invention, a silicon-based polymer layer is formed by coating formation on a light shielding film laminated on a light shielding film of a binary mask blank or a halftone material film of a halftone phase shift mask blank. Therefore, it is possible to provide mask blanks that form a mask pattern that is excellent in dimensional accuracy of a fine pattern and that has a high uniformity of in-plane distribution of dimensions at low cost.
According to the photomask blank of the present invention, it is possible to obtain a photomask having improved resolution and pitch-dependent CD characteristics without changing the current resist.

According to the photomask manufacturing method according to the present invention, the silicon-based polymer layer of the mask blank of the present invention has a high resistance to dry etching with a chlorine-based gas, so that a resist film coated and formed thereon is thinner than the conventional method. Thus, the resolution of the mask pattern can be improved.
Further, since the margin of the mask manufacturing process is greatly increased, the CD error (shift amount) due to the pattern density difference in the dry etching is reduced, and it is fine and excellent in CD dimensional accuracy, and the uniformity of the in-plane distribution of the CD is high. A photomask having a mask pattern can be obtained.

According to the manufacturing method according to the present invention, it is possible to improve the resolution and the CD density characteristic without changing the current resist.
Further, in the photomask manufacturing method of the present invention using a halftone material film whose main component is a compound that can be dry-etched by a fluorine-based gas, a light-shielding film is formed when the lower halftone material film is patterned by dry etching. The upper silicon-based polymer layer is also etched at the same time, so that the silicon-based polymer layer does not remain on the completed photomask, and there is an effect on the manufacturing process that the removal of the silicon-based polymer layer is unnecessary.

The photomask manufacturing method according to the present invention can be used as a manufacturing technique of a semiconductor element photomask having a half pitch of 65 nm or more, and can be further applied to a photomask manufacturing technique for a half pitch of 45 nm and 32 nm. Various resist processes can be handled by changing the resist.
Therefore, it can be applied not only to photomask manufacturing but also to semiconductor device manufacturing.

It is a cross-sectional schematic diagram which shows an example of 1st Embodiment of the photomask blank of this invention. It is a cross-sectional schematic diagram which shows an example of 2nd Embodiment of the photomask blank of this invention. It is process cross-sectional schematic diagram which shows one Embodiment of the manufacturing method of the photomask using the photomask blank of the 1st Embodiment of this invention. FIG. 4 is a process cross-sectional schematic diagram illustrating one embodiment of a photomask manufacturing method following FIG. 3. It is process cross-sectional schematic diagram which shows one Embodiment of the manufacturing method of the photomask using the photomask blank of the 2nd Embodiment of this invention. FIG. 6 is a process cross-sectional schematic diagram illustrating an embodiment of a photomask manufacturing method following FIG. 5. It is an enlarged view of the pattern for evaluation used for the Example and comparative example of this invention. It is CD shift amount in the dry etching of the Example of this invention, and a comparative example.

  Hereinafter, with reference to the drawings, an embodiment of a photomask blank of the present invention and a method of manufacturing a photomask using the same will be described.

(Photomask blanks)
(First embodiment)
FIG. 1 is a schematic cross-sectional view showing an example of the first embodiment of the photomask blank of the present invention.
As shown in FIG. 1, the photomask blank of the present invention includes a transparent substrate 11, a light shielding film 13 formed on one main surface of the transparent substrate 11, and a non-photosensitive silicon-based polymer on the light shielding film 13. The layer 14 is provided by coating formation, and the silicon-based polymer layer 14 is characterized by having high resistance to dry etching by chlorine-based gas.
Moreover, as a form of the photomask blank of the present invention, a photomask blank with a resist in which an electron beam resist is further laminated on the silicon-based polymer layer 14 may be used.

(Second Embodiment)
FIG. 2 is a schematic cross-sectional view showing an example of the second embodiment of the photomask blank of the present invention.
As shown in FIG. 2, the photomask blank of the present invention is laminated on a transparent substrate 21, a halftone material film 22 laminated on one main surface of the transparent substrate 21, and the halftone material film 22. The light-shielding film 23 and a non-photosensitive silicon-based polymer layer 24 are formed on the light-shielding film 23 by coating, and the silicon-based polymer layer 24 has a high resistance to dry etching with a chlorine-based gas. It is.
Moreover, as a form of the photomask blank of the present invention, a photomask blank with a resist in which an electron beam resist is further laminated on the silicon-based polymer layer 24 may be used.

Next, each element constituting the photomask blank of the first embodiment and the second embodiment of the present invention will be described.
In the photomask blank of the present invention, optically polished synthetic quartz glass, fluorite, calcium fluoride, or the like can be used as the transparent substrates 11 and 21. However, the transparent substrates 11 and 21 are usually used frequently, have stable quality, and are short. Synthetic quartz glass having a high transmittance for exposure light having a wavelength is more preferable.

In the photomask blank of the present invention, as the light shielding films 13 and 23, a chromium-based film mainly composed of chromium that has been used most frequently is more preferable from the viewpoint of cost and quality of the mask blank.
As the chromium-based film, a single layer film made of a material selected from chromium, chromium oxide, chromium nitride, and chromium oxynitride is usually used. Among these chromium-based films, film formation is easy and versatile. A chromium film or a chromium nitride film that can easily reduce film stress is more preferable.
For example, when chromium is used as the light-shielding film, the film thickness is in the range of about 45 nm to 100 nm. In order to form a fine pattern, it is more preferable that the film thickness is smaller.
This is because if the thickness of the light shielding films 13 and 23 is less than 45 nm, the light shielding performance after the mask fabrication is insufficient, while if the film thickness exceeds 100 nm, the resolving power as the light shielding film pattern decreases.

  In the photomask blank of the second embodiment of the present invention, the light shielding film 23 functions as an antistatic layer at the time of electron beam drawing, is used as a mask at the time of dry etching of the halftone material film 22, and is necessary after forming the mask pattern. Accordingly, it is partially left and used for light shielding during semiconductor device exposure.

In the photomask blank of the second embodiment of the present invention, the halftone material film 22 is mainly composed of a compound that can easily obtain a desired halftone characteristic and can be dry etched with a fluorine-based gas, and has excellent dry etching processing characteristics. A thin film having a large etching selectivity with respect to the light shielding film 23 is preferable.
For example, as the halftone material film 22 mainly composed of a molybdenum silicide compound, a light semi-transmissive film such as a molybdenum silicide oxide film (MoSiO), a molybdenum silicide nitride film (MoSiN), a molybdenum silicide oxynitride film (MoSiON), or the like can be given. .
Further, examples of the halftone material film include a tantalum film such as a tantalum hafnium film, and a thin film such as silicon oxynitride.

  The film thickness of the halftone material film 22 is, for example, a film thickness in the range of about 60 nm to 100 nm when a molybdenum silicide compound is used. More preferably, when the exposure light is a KrF excimer laser, In the case of an ArF excimer laser, a film thickness in the range of about 80 nm to 90 nm is used.

In the photomask blank of the present invention, the silicon-based polymer layers 14 and 24 include a siloxane structure (Si—O—Si), a trialkylsilyl structure, a trialkoxysilyl structure, or a polysilane structure. What has a polymer as a main component is preferable.
These silicon-based polymer layers 14 and 24 can be obtained by coating and forming a solution containing a polymer having the above structure as a main component on the light shielding films 13 and 23 by a method such as spin coating.
The solution containing the polymer is composed of a polymer, a crosslinking agent and a solvent, and may further contain a crosslinking catalyst, a surfactant and the like as necessary.
In the present invention, since the silicon-based polymer layers 14 and 24 are formed in a pattern by dry etching, photosensitivity is not required, and it is desirable that they are non-photosensitive in a normal ultraviolet light or visible light region from the viewpoint of operability. .
Further, the silicon-based polymer layers 14 and 24 need not be sensitive to an electron beam for mask drawing, and are preferably non-electron sensitive.
In the present invention, non-photosensitivity and non-electron-sensitive are collectively referred to as non-photosensitivity.

A silicon-based polymer having a siloxane structure can be generally obtained by synthesis by a hydrolysis reaction of a silane compound.
The details of the structure of the silicon-based polymer having a siloxane structure used in the present invention are not particularly limited, but a siloxane ladder polymer is more preferable in terms of easy formation of a dense coating film, and an organo group having an organic group as a substituent on a silicon atom. More preferred is a siloxane polymer.
For example, specific examples of silicon-based polymers having a siloxane structure include methyl siloxane, methyl silsesquioxane, phenyl siloxane, phenyl silsesquioxane, methyl phenyl siloxane, methyl phenyl silsesquioxane polymers, and hydrogen. Examples thereof include siloxane polymers and hydrogen silsesquioxane polymers.

  As a silicon-based polymer having a trialkylsilyl structure or a trialkoxysilyl structure, examples of the silicon-containing monomer component include vinyltrimethoxysilane, allyltrimethylsilane, 2- (trimethylsiloxy) ethyl methacrylate, and 3-methacryloxypropylmethyldimethoxy. Silane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, allylaminotrimethyl Examples include silane and allyldimethylpiperidinomethylsilane.

As the silicon-based polymer having a polysilane structure, a silicon-based polymer having a Si—Si bond in the main chain is suitable, and may be any of a chain, a ring, and a branch.
In the above polysilane structure, the side chain preferably has a hydrogen atom, a substituted or unsubstituted hydrocarbon group, an alkoxy group or the like. Examples of the hydrocarbon group include an aliphatic, alicyclic or aromatic hydrocarbon group. Is used.
In the case of an aliphatic or alicyclic hydrocarbon group, examples include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a cyclopentyl group, and a cyclohexyl group.
Examples of the aromatic hydrocarbon group include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, a benzyl group, and a phenethyl group.
In addition, as a substituted hydrocarbon group, what substituted a part or all of the hydrogen atom of the unsubstituted hydrocarbon group illustrated above by the alkoxy group etc. is mentioned.
Examples of the alkoxy group include a methoxy group, an ethoxy group, and an isopropoxy group.

Moreover, as a silicon type polymer used for formation of the silicon type polymer layer of this invention, the polymer which copolymerized the other monomer component as needed can also be used.
For example, acrylic acid, methacrylic acid, acrylic acid ester compounds, methacrylic acid ester compounds, vinyl compounds and the like can be mentioned.

The silicon polymer used in the present invention preferably further contains a crosslinking agent.
Examples of the crosslinking agent include melamine-based and substituted urea-based crosslinking agents such as hexamethoxymethylmelamine or tetramethoxymethylglycoluril.

Examples of the solvent for dissolving solids such as a silicon-based polymer used in the present invention include monohydric alcohols such as methanol and propanol, alkylcarboxylic acid esters such as ethyl-3-ethoxypropionate, ethylene glycol, and diethylene glycol. Polyhydric alcohols, monoethers of polyhydric alcohols such as ethylene glycol monomethyl ether and diethylene glycol monomethyl ether, esters such as ethyl acetate and butyl acetate, ketones such as acetone and methyl ethyl ketone, polyvalents such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether Examples include alcohol ethers.
Said organic solvent is used individually or in combination of 2 or more types.
The content of the organic solvent is not particularly limited, and can be appropriately set according to coating characteristics and coating film thickness.
Generally, it is used in the range whose solid content concentration mainly includes a silicon-based polymer excluding a solvent is about 1 to 30% by weight.

In the photomask blank of the present invention, it is preferable that the silicon-based polymer layers 14 and 24 formed on the light-shielding films 13 and 23 are heat-treated after application to remove the solvent component.
In the photomask blank of the present invention, the film thickness of the silicon-based polymer layers 14 and 24 is preferably in the range of 10 nm to 100 nm.
When the film thickness of the silicon-based polymer layers 14 and 24 is less than 10 nm, the resistance to dry etching of the lower light-shielding films 13 and 23 is insufficient. On the other hand, when the film thickness exceeds 100 nm, the silicon-based polymer layers This is because the resolving power at the time of pattern processing of the layers 14 and 24 decreases.

Moreover, in the photomask blank of the second embodiment of the present invention, the film thickness of the silicon-based polymer layer 24 is preferably smaller than the film thickness of the halftone material film 22.
This is because the silicon-based polymer layer 24 can be more reliably removed by etching simultaneously with the pattern etching of the halftone material film 22.

In addition, as a form of the blank in the present invention, a photomask blank with a resist in which a resist such as an electron beam resist (not shown in FIGS. 1 and 2) is further laminated on the silicon-based polymer layers 14 and 24. There may be.
In this case, the film thickness of the resist can be made thinner than a normal film thickness that does not use the silicon-based polymer layers 14 and 24, and can be used in the film thickness range of 100 nm to 300 nm.

(Photomask manufacturing method)
(First embodiment)
FIG. 3 and subsequent FIG. 4 are process cross-sectional schematic diagrams showing an embodiment of a photomask manufacturing method using the photomask blank of the first embodiment of the present invention.
3 and 4 show a case where a photomask is manufactured using the photomask blanks shown in FIG. 1, the same reference numerals are used for the same portions as those in FIG. 1.
Hereinafter, it demonstrates in order, referring drawings.

  As shown in FIG. 3A, a light shielding film 13 is laminated on the transparent substrate 11 to form a film. The light shielding film 13 can be formed by a conventionally known method. For example, in the case of chromium, the light shielding film 13 can be formed by a sputtering method using a chromium target.

Next, as shown in FIG. 3B, a silicon polymer is applied and formed on the light shielding film 13 by a method such as spin coating, and a silicon polymer layer 14 is provided by heat treatment.
As described above, the film thickness of the silicon-based polymer layer 14 is preferably in the range of 10 nm to 100 nm.

Next, as shown in FIG. 3C, a resist film 15 such as an electron beam resist is formed on the silicon polymer layer by a method such as spin coating.
As a resist such as an electron beam resist, either a negative type or a positive type can be applied.
In this manufacturing method, since the resist film 15 is used only for dry etching of the silicon-based polymer layer 14, the resist film 15 can be applied thinner than a normal coating thickness and used as a thin layer.
For example, in the case of normal dry etching not using the silicon-based polymer layer 14, the thickness of the resist film needs to be about 300 nm, and if it is less than 300 nm, the resist film may be reduced during the dry etching of the light shielding film 13 in some cases. In severe cases, there is a risk of disappearance during the etching process.
On the other hand, in this manufacturing method, even if the film thickness of the resist film 15 is in the range of 100 nm to 300 nm, a fine pattern can be formed with almost no damage to the resist film 15 during dry etching of the silicon-based polymer layer 14.
This is because when the film thickness of the resist film 15 is less than 100 nm, the resistance to dry etching is insufficient, and when the film thickness exceeds 300 nm, the resolution of the resist pattern decreases.

Next, after the resist film is pre-baked, a pattern is drawn with an electron beam 16 by an electron beam drawing apparatus (FIG. 3D), and the resist is developed with a predetermined developer to form a resist pattern 15a (FIG. 3E). ).
At the time of electron beam drawing, the light shielding film 13 prevents the substrate from being charged and exhibits the effect of drawing the drawing pattern precisely.

Next, as shown in FIG. 4F, the silicon-based polymer layer 14 is patterned by dry etching using the resist pattern 15a as a mask to form a silicon-based polymer pattern 14a.
The silicon-based polymer layer 14 can be dry-etched by using a gas such as CF ₄ , CHF ₃ , C ₂ F ₆ , a mixed gas thereof, or a gas obtained by mixing oxygen in these gases as an etching gas. it can.

Next, after stripping the resist pattern 15a (FIG. 4G), the light shielding film 13 is dry-etched using the silicon-based polymer pattern 14a as a mask to form the light shielding film pattern 13a (FIG. 4H).
When the light shielding film 13 is chromium, dry etching can be performed by using conventionally known chlorine or a mixed gas of chlorine and oxygen as an etching gas.
In this manufacturing method, the dry etching resistance of the silicon-based polymer pattern 14a with chlorine-based gas is more than twice that of a commonly used resist film, for example, the resist pattern 15a.
For this reason, the light shielding film 13 can be finely patterned.

  Next, as shown in FIG. 4I, the silicon-based polymer pattern 14a on the light shielding film pattern 13a is removed by etching to obtain a binary photomask in which the light shielding film pattern 13a is formed on the transparent substrate 11.

  In the above manufacturing method, the step of stripping the resist pattern 15a shown in FIG. 4G is replaced with the step of dry-etching the light shielding film 13 shown in FIG. 4H to form the light shielding film pattern 13a. It is also possible to strip the resist pattern 15a after forming the film pattern 13a.

(Second Embodiment)
FIG. 5 and subsequent FIG. 6 are process cross-sectional schematic diagrams showing an embodiment of a photomask manufacturing method using the photomask blank of the second embodiment of the present invention.
5 and 6 show a case where a photomask is manufactured using the photomask blank shown in FIG. 2, and the same reference numerals are used for the same portions as in FIG.
In the second embodiment, the process up to patterning the light shielding film laminated on the halftone material film is the same as the process of forming the light shielding film pattern described in the first embodiment. Hereafter, it demonstrates again in order, referring drawings.

  As shown in FIG. 5A, a halftone material film 22 is formed on a transparent substrate 21, and a light shielding film 23 is further formed thereon. The light shielding film 23 is preferably made of a material having a high selectivity when the halftone material film 22 is dry-etched.

  The halftone material film 22 can be formed by a conventionally known method. For example, in the case of a molybdenum silicide oxide film (MoSiO), a mixed target of molybdenum and silicon (Mo: Si = 1: 2 mol%) is used, and argon is used. It can be formed by a reactive sputtering method in a mixed gas atmosphere of oxygen and oxygen.

  The light shielding film 23 can be formed by a conventionally known method. For example, in the case of chromium, it can be formed by a sputtering method using a chromium target.

Next, as shown in FIG. 5B, a silicon-based polymer is applied and formed on the light-shielding film 23 by a method such as spin coating, and a silicon-based polymer layer 24 is provided by heat treatment.
As described above, the film thickness of the silicon-based polymer layer 24 is smaller than the film thickness of the halftone material film 22, and the film thickness of the silicon-based polymer layer 24 is preferably in the range of 10 nm to 100 nm.

Next, as shown in FIG. 5C, a resist film 25 such as an electron beam resist is formed on the silicon-based polymer layer by a method such as spin coating. As a resist such as an electron beam resist, either a negative type or a positive type can be applied.
In this manufacturing method, since the resist film 25 is used only for dry etching of the silicon-based polymer layer 24, the resist film 25 can be applied thinner than a normal coating thickness and used as a thin layer.
For example, in the case of normal dry etching that does not use the silicon-based polymer layer 24, the thickness of the resist film needs to be about 300 nm, and if it is less than 300 nm, the resist film may be reduced during the dry etching of the light shielding film 23 depending on the case. In severe cases, there is a risk of disappearance during the etching process.
On the other hand, in this manufacturing method, even if the film thickness of the resist film 25 is in the range of 100 nm to 300 nm, a fine pattern can be formed with almost no damage to the resist film 25 during dry etching of the silicon-based polymer layer 24.
This is because when the film thickness of the resist film 25 is less than 100 nm, the resistance to dry etching is insufficient, and when the film thickness exceeds 300 nm, the resolution of the resist pattern decreases.

Next, after the resist film is pre-baked, a pattern is drawn with an electron beam 26 by an electron beam drawing apparatus (FIG. 5D), and the resist is developed with a predetermined developer to form a resist pattern 25a (FIG. 5E). ).
At the time of electron beam drawing, the light shielding film 23 prevents the substrate from being charged and exhibits an effect of drawing a drawing pattern precisely.

Next, as shown in FIG. 6F, the silicon-based polymer layer 24 is patterned by dry etching using the resist pattern 25a as a mask to form a silicon-based polymer pattern 24a.
The silicon-based polymer layer 24 can be dry-etched by using a gas such as CF ₄ , CHF ₃ , C ₂ F ₆ , a mixed gas thereof, or a gas obtained by mixing oxygen in these gases as an etching gas. it can.

Next, after stripping the resist pattern 25a (FIG. 6G), the light shielding film 23 is dry-etched using the silicon-based polymer pattern 24a as a mask to form the light shielding film pattern 23a (FIG. 6H).
When the light shielding film 23 is chromium, dry etching can be performed by using conventionally known chlorine or a mixed gas of chlorine and oxygen as an etching gas.
In this manufacturing method, the dry etching resistance of the silicon-based polymer pattern 24a by the chlorine-based gas is twice or more that of a resist film that is usually used, for example, the resist pattern 25a.
For this reason, the light shielding film 23 can be finely patterned.

  In the above manufacturing method, the step of stripping the resist pattern 25a shown in FIG. 6G is replaced with the step of forming the light shielding film pattern 23a by dry etching the light shielding film 23 shown in FIG. It is also possible to strip the resist pattern 25a after forming the film pattern 23a.

Next, as shown in FIG. 6I, the halftone material film 22 is patterned by dry etching using the light shielding film pattern 23a as a mask.
At the same time, the silicon-based polymer pattern 24a on the light shielding film pattern 23a is also dry etched. FIG. 6 (i) is a diagram showing an intermediate stage of dry etching, and shows a state where the halftone material film 22 is etched and the silicon-based polymer pattern 24a is also etched to reduce the film thickness.

Next, as shown in FIG. 6J, the halftone material film 22 is patterned by dry etching using the light shielding film pattern 23a as a mask to form a halftone mask pattern 22a, and at the same time, silicon on the light shielding film pattern 23a is formed. The system polymer pattern 24a is removed by dry etching.
Normally, the silicon-based polymer pattern 24a is etched faster than the halftone material film 22, and in the preferred form of the present manufacturing method, the film thickness of the silicon-based polymer layer is smaller than the film thickness of the halftone material film.
Therefore, the half-tone material film 22 is not etched due to excessive etching of the half-tone material film 22 due to the remaining silicon-based polymer pattern 24a or damage to the exposed transparent substrate 21 surface. It can be patterned with proper etching.

The halftone material film 22 is a gas such as CF ₄ , CHF ₃ , or C ₂ F _{6 that} is usually used for a halftone material film made of a molybdenum silicide compound, a mixed gas thereof, or a mixture of these gases with oxygen. Dry etching can be performed by using a gas as an etching gas.

  That is, in this manufacturing method, the etching gas for the halftone material film 22 and the etching gas for the silicon-based polymer pattern 24a are made the same, and the halftone material film 22 and the silicon-based polymer pattern 24a are simultaneously dry-etched to thereby achieve phase shift. The formation of the mask pattern 22a of the mask and the removal of the unnecessary silicon-based polymer pattern 24a are simultaneously performed to shorten the manufacturing process and improve the quality.

Next, as shown in FIG. 6K, part or all of the light shielding film pattern 23a is removed by etching to obtain a halftone phase shift mask having the halftone mask pattern 22a.
In general, the light shielding film pattern 23a is often used for light shielding at the time of exposure of a semiconductor device, while remaining partially on the outer periphery of the mask.

Example 1
An optically polished 6 inch square, 0.25 inch thick transparent synthetic quartz substrate is cleaned, and a layer containing molybdenum silicide compound as a main component and containing oxygen as a halftone material film on one main surface is as follows: Formed under conditions. Here, the film thickness was set to 70 nm for an ArF excimer laser in order to obtain a transmittance of 6% and a phase difference of 180 degrees.
<Sputtering conditions for halftone material film>
Film forming apparatus: Planar type DC magnetron sputtering apparatus Target: Molybdenum: Silicon = 1: 4 (atomic ratio)
Gas and flow rate: argon gas 50 sccm + oxygen gas 50 sccm
Sputtering pressure: 0.3 Pascal Sputtering current: 3.5 Ampere

Next, a light shielding film made of chromium was laminated on the halftone material film to a thickness of 50 nm under the following conditions.
<Sputtering conditions for light shielding film>
Film forming apparatus: Planar type DC magnetron sputtering apparatus Target: Metal chromium Gas and flow rate: Argon gas 50 sccm
Sputtering pressure: 0.3 Pascal Sputtering current: 3.5 Ampere

Next, a silicon-based polymer is spin-coated on the light-shielding film, and then heated at 190 ° C. for 16 minutes to form a silicon-based polymer layer having a thickness of 40 nm. Halftone phase shift for ArF excimer laser exposure Mask blanks were used.
As the silicon-based polymer, a solution in which a siloxane polymer obtained by reacting tetramethoxysilane and methyltrimethoxysilane was dissolved in a mixed solvent containing equal amounts of n-butanol and methyl-3-methoxypropionate was used.

Next, an electron beam resist was applied on the mask blanks to a thickness of 300 nm, prebaked, and then subjected to pattern exposure with an electron beam drawing apparatus and developed to form a resist pattern having a desired shape.
In this production method, intermixing between the silicon-based polymer layer and the electron beam resist did not occur, and the resolution of the resist was not affected.

Next, using the resist pattern as a mask, the silicon-based polymer layer exposed from the resist pattern was dry-etched and patterned under the following conditions using a dry etching apparatus.
<Silicon polymer layer etching conditions>
Etching gas CF ₄
Gas pressure 10mTorr
ICP power (high density plasma generation) 950W
Bias power (drawer power) 50W

Next, after peeling off the resist pattern with oxygen plasma, the exposed chromium light-shielding film with the patterned silicon polymer layer as a mask was dry-etched under the following conditions to form a chromium light-shielding film pattern.
<Chrome light shielding film etching conditions>
Etching gas Cl ₂ + O ₂ gas (2: 3)
Pressure 10mTorr
ICP power (high density plasma generation) 500W
Bias power (drawer power) 25W

Next, the halftone material film exposed by using the light shielding film pattern as a mask was patterned by dry etching under the following conditions to form a mask pattern, and at the same time, patterned to be laminated on the light shielding film pattern. The silicon-based polymer layer was removed by dry etching. The etched cross-sectional shape was substantially vertical, and a very fine mask pattern was formed.
<Etching conditions for halftone material film and silicon polymer layer>
Etching gas CF ₄
Gas pressure 10mTorr
ICP power (high density plasma generation) 950W
Bias power (drawer power) 50W

Next, a photosensitive resist is applied on the substrate subjected to the above steps, and a resist pattern layer having an opening only in a region to be exposed from the chromium light-shielding film is formed by photolithography, and then a cerium nitrate wet etchant is formed. Wet etching was performed with (MR-ES manufactured by The Inktec Co., Ltd.), and the chromium light-shielding film was selectively removed to obtain a halftone phase shift mask.
The halftone phase shift mask according to the present embodiment has a structure in which a mask pattern is formed by a halftone phase shift layer mainly composed of a molybdenum silicide compound on a synthetic quartz substrate, and a chromium light-shielding film is laminated on a part thereof. It is what makes.
On the halftone phase shift mask of this example, a pattern with a changed pitch was formed for CDU evaluation as shown in FIG. FIG. 7 is an enlarged schematic view illustrating a pattern (7-1) having a dense space width and a sparse pattern (7-2) included in the evaluation pattern.
In FIG. 7, the black portion on the paper indicates a halftone portion or a light shielding portion.

(Comparative example)
The substrate up to the stage where the light shielding film made of chromium was formed on the halftone material film mainly composed of the molybdenum silicide compound shown in Example 1 was used as a comparative example, and the halftone phase shift mask blank of the comparative example was used. This blank as a comparative example in which no silicon polymer layer is provided has a conventionally known configuration. A halftone phase shift mask was obtained by processing by a conventional method using a blank of a comparative example in which no silicon polymer layer was provided.
The appearance of this halftone phase shift mask as a comparative example is the same as that of the halftone phase shift mask of Example 1, and is masked by a halftone phase shift layer mainly composed of a molybdenum silicide compound on a synthetic quartz substrate. A pattern is formed, and further a chromium light shielding film is laminated on a part of the pattern.
Example 1 and the comparative example differed in appearance as blanks, but there was no difference in appearance when used as a photomask.
Similarly to Example 1, the halftone phase shift mask of the comparative example also formed a pattern with a changed pitch as shown in FIG. 7 for CDU evaluation.

The CD of the pattern in which the space width of the halftone phase shift mask of Example 1 and the comparative example was changed was measured.
The result is shown in FIG.
FIG. 8 shows the dimensional shift difference due to dry etching as the CD error (shift amount) from the resist pattern CD to the mask pattern CD when the space width of the adjacent pattern is in the range of approximately 200 nm to 10000 nm.
The horizontal axis of FIG. 8 shows the space width (nm) of the pattern shown in FIG. 7, and the vertical axis shows the CD shift amount (nm). In Example 1 and Comparative Example, each pattern has three lines. , Seven cases are illustrated.

In addition, in FIG. 8, reading values of the CD shift amount in a fine region having a space width of 280 nm to 4000 nm are shown in Table 1.
In Table 1, in the case of Example 1 (A: 7 lines, B: 3 lines) and the comparative example (C: 7 lines, D lines), the pattern lines are divided into 7 cases and 3 lines. : 3) shows the CD shift amount.

As shown in FIG. 8 and Table 1, the CD shift amount according to Example 1 (A, B) of the present invention is shifted due to the difference in the space width of the pattern as compared with the conventional method as Comparative Example (C, D). The amount was greatly reduced to about 1/3, and uniform etching was performed without depending much on the density of the pattern, and it was shown that the uniformity of CD including a minute dimension was good.
On the other hand, it has been shown that the conventional method greatly depends on the density of the pattern, and the change in the CD shift amount is remarkable particularly in the region where the space width is small.
That is, although it has been difficult to produce a photomask with high CD uniformity including a dense pattern by the conventional method, the mask blank of the present invention is used, and the production method of the present invention is excellent in the precision of fine patterns, It was possible to obtain a photomask having a mask pattern with high CD uniformity including
In the present embodiment, the total shift amount is about 5 nm larger than that of the conventional method, but this can be easily improved by offsetting the pattern design in advance or by optimizing the etching conditions for this material.

  As described above, according to the manufacturing method of the present invention using the photomask blanks of the present invention, a mask having a mask pattern having excellent dimensional accuracy of important micropatterns and high uniformity of in-plane distribution of dimensions. It has been shown that it can be manufactured at low cost and is an effective method for manufacturing a photomask with a half pitch of 65 nm or more, particularly 45 nm or more.

11, 21 Transparent substrate 13, 23 Light shielding film 13a, 23a Light shielding film pattern 14, 24 Silicon polymer layer 14a, 24a Silicon polymer pattern 15, 25 Resist film 15a, 25a Resist pattern 16, 26 Electron beam 22 Halftone material film 22a Halftone mask pattern

Claims (7)

A photomask blank in which at least a light shielding film is formed on one main surface of a transparent substrate,
A non-photosensitive silicon-based polymer layer is formed on the light-shielding film with a thickness in the range of 10 nm to 100 nm,
An electron beam resist film is laminated on the silicon polymer layer,
The photomask brands, wherein the silicon-based polymer layer includes a siloxane ladder polymer, or a silicon-based polymer having a trialkylsilyl structure, a trialkoxysilyl structure, or a polysilane structure.   The photomask blank according to claim 1, wherein the light shielding film contains chromium.   The photomask blank according to claim 1, wherein the light shielding film is formed by being laminated on a halftone material film.   4. The photomask blank according to claim 3, wherein a film thickness of the silicon-based polymer layer is smaller than a film thickness of the halftone material film.   5. The photomask blank according to claim 3, wherein the halftone material film includes a compound that can be dry-etched by a fluorine-based gas.   6. The photomask blank according to claim 1, wherein a thickness of the electron beam resist film is in a range of 100 nm to 300 nm. 7. The photomask blank according to claim 1, wherein a dry etching resistance of the silicon-based polymer layer by a chlorine-based gas is twice or more that of the electron beam resist film.

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