WO2018123939A1 - Halftone mask, photomask blank, and method for manufacturing halftone mask - Google Patents

Halftone mask, photomask blank, and method for manufacturing halftone mask Download PDF

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Publication number
WO2018123939A1
WO2018123939A1 PCT/JP2017/046369 JP2017046369W WO2018123939A1 WO 2018123939 A1 WO2018123939 A1 WO 2018123939A1 JP 2017046369 W JP2017046369 W JP 2017046369W WO 2018123939 A1 WO2018123939 A1 WO 2018123939A1
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Prior art keywords
film
phase shift
semi
etching
transmissive
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PCT/JP2017/046369
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French (fr)
Japanese (ja)
Inventor
慎吾 山田
久美子 森山
昌宏 美作
Original Assignee
株式会社エスケーエレクトロニクス
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Application filed by 株式会社エスケーエレクトロニクス filed Critical 株式会社エスケーエレクトロニクス
Priority to KR1020197010544A priority Critical patent/KR102193360B1/en
Priority to CN201780070660.9A priority patent/CN109983402B/en
Publication of WO2018123939A1 publication Critical patent/WO2018123939A1/en

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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F1/00—Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
    • G03F1/26—Phase shift masks [PSM]; PSM blanks; Preparation thereof
    • G03F1/32—Attenuating PSM [att-PSM], e.g. halftone PSM or PSM having semi-transparent phase shift portion; Preparation thereof
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F1/00—Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F1/00—Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
    • G03F1/68—Preparation processes not covered by groups G03F1/20 - G03F1/50
    • G03F1/80—Etching
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/26—Processing photosensitive materials; Apparatus therefor
    • G03F7/40—Treatment after imagewise removal, e.g. baking
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/708—Construction of apparatus, e.g. environment aspects, hygiene aspects or materials
    • G03F7/7095—Materials, e.g. materials for housing, stage or other support having particular properties, e.g. weight, strength, conductivity, thermal expansion coefficient
    • G03F7/70958—Optical materials or coatings, e.g. with particular transmittance, reflectance or anti-reflection properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/027—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
    • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
    • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
    • H01L21/76801—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing
    • H01L21/76829—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing characterised by the formation of thin functional dielectric layers, e.g. dielectric etch-stop, barrier, capping or liner layers

Definitions

  • the present invention relates to a halftone mask, a photomask blank, and a halftone mask manufacturing method, which are multi-tone photomasks used for flat panel displays and the like.
  • a multi-tone photomask called a halftone mask having a function of limiting an exposure amount by the transmittance of a semi-transmissive film is used.
  • the halftone mask uses a transflective film having an intermediate transmittance between the transparent substrate and the light shielding film, and a multi-tone photomask having three or more gradations is formed by the transparent substrate, the semitransmissive film, and the light shielding film. Can be realized.
  • photoresist patterns having different film thicknesses can be formed by a single exposure, and the number of lithography processes in the flat panel display manufacturing process can be reduced.
  • manufacturing costs can be reduced.
  • a lithography process is performed by forming photoresist patterns having different film thicknesses in a single exposure process in the channel region and source / drain electrode formation region of the TFT. As a technique, the manufacturing cost is thereby reduced.
  • the halftone mask can contribute to the reduction of the lithography process, the change in the intensity distribution of the exposure light at the boundary between the semi-transmissive film and the light-shielding film is relatively gradual, so that exposure is performed using the half-tone mask.
  • the photoresist film has a problem that the cross-sectional shape at the portion corresponding to the boundary shows a gentle inclination, the process margin is lowered, and it is difficult to form a fine pattern.
  • phase shift mask is a technique for a binary mask, it is impossible to reduce the lithography process like a halftone mask. Therefore, when used for manufacturing a flat panel display, it cannot contribute to the reduction of the lithography process.
  • an object of the present invention is to provide a photomask, a photomask blank used for manufacturing the photomask, and a method for manufacturing the photomask that can achieve both reduction of the lithography process and further miniaturization of the pattern.
  • the photomask according to the embodiment of the present invention is Having a transflective part, a phase shift part, a boundary part and a translucent part on a transparent substrate;
  • the translucent part consists of a portion where the transparent substrate is exposed,
  • the semi-transmissive portion is formed of a semi-transmissive film provided on the transparent substrate,
  • the phase shift part is formed of a phase shift film provided on the transparent substrate,
  • the boundary portion is formed in a region where the semi-transmissive portion and the phase shift portion are adjacent to each other,
  • the width of the boundary is not more than a certain width;
  • the boundary portion is formed of a laminated structure film in which the phase shift film, the etching stopper film, and the semi-transmissive film are formed in this order, while the semi-transmissive portion, the phase shift portion, and the transparent portion excluding the boundary portion.
  • the etching stopper film of the optical part is removed,
  • the width of the boundary portion is not more than a resolution limit of
  • the photomask according to the embodiment of the present invention is A transparent substrate has a semi-transmissive part, a phase shift part, a boundary part, and a translucent part,
  • the translucent part consists of a portion where the transparent substrate is exposed
  • the semi-transmissive part is formed of a semi-permeable film provided on the transparent substrate
  • the phase shift part is formed of a phase shift film provided on the transparent substrate
  • the boundary portion is formed in a region where the semi-transmissive portion and the phase shift portion are adjacent to each other,
  • the width of the boundary is not more than a certain width; In the boundary portion, the semi-transmissive film, the etching stopper film, and the phase shift film are formed in this order, while the semi-transmissive portion, the phase shift portion, and the light transmitting portion except for the boundary portion are etched stopper films. Is removed,
  • the width of the boundary portion is not more than a resolution limit of a projection exposure apparatus in which the photomask is used.
  • the photomask according to the embodiment of the present invention is 3.
  • the photomask according to the embodiment of the present invention is The translucent film has a transmittance with respect to exposure light of 10 to 60%.
  • the transflective portion has a light transmittance intermediate between the phase shift portion and the translucent portion, and a multi-tone photomask is obtained by the transflective portion, the phase shift portion, and the translucent portion.
  • a multi-tone photomask is obtained by the transflective portion, the phase shift portion, and the translucent portion.
  • the photomask according to the embodiment of the present invention is
  • the phase shift film and the semi-transmissive film can be etched with the same etching solution, and the etching stopper film has an etching selectivity with respect to the etching solution.
  • the etching stopper film is made of a Ti-based film
  • the phase shift film is made of a Cr oxide film.
  • the photomask can be easily manufactured using wet etching in the photomask manufacturing process.
  • the photomask according to the embodiment of the present invention is The width of the boundary portion is set to an alignment error of a photomask drawing apparatus and is equal to or less than a resolution limit of a projection exposure apparatus in which the photomask is used.
  • the semi-transmissive portion and the phase shift portion can be adjacent to each other without the etching stopper film at the boundary portion having an adverse effect on the exposure of the photoresist.
  • the photomask blank according to the embodiment of the present invention is Photomask blanks for manufacturing the photomask, The phase shift film and the etching stopper film are laminated in this order on the transparent substrate.
  • a multi-tone mask can be formed on a photomask blank by forming a transflective film according to customer specifications and applications. As a result, it is possible to shorten the manufacturing period of a photomask having desired characteristics having both a halftone effect and a phase shift effect.
  • a photomask manufacturing method includes: A step of laminating a phase shift film and an etching stopper film in this order on a transparent substrate; Forming a first photoresist film; Patterning the first photoresist film; Etching the etching stopper film using the first photoresist film as a mask; Etching the phase shift film using the etching stopper film as a mask; Removing the first photoresist film; Forming a semipermeable membrane; Forming a second photoresist film; Patterning the second photoresist film so as to have an overlap of the etched stopper film and the width below the resolution limit of the projection exposure apparatus; Etching the semi-transmissive film using the second photoresist film as a mask; Removing the second photoresist film; Etching the etching stopper film on the phase shift film using the semi-transmissive film as a mask, and removing the etching stopper film excluding the boundary portion.
  • a photomask manufacturing method includes: A step of laminating a semi-transmissive film and an etching stopper film in this order on a transparent substrate; Forming a third photoresist film; Patterning the third photoresist film; Etching the etching stopper film using the third photoresist film as a mask; Etching the semi-transmissive film using the etching stopper film as a mask; Removing the third photoresist film; Forming a phase shift film; Forming a fourth photoresist film; Patterning the fourth photoresist film so as to have an overlap of the etched stopper film and the width below the resolution limit of the projection exposure apparatus; Etching the phase shift film using the fourth photoresist film as a mask; Removing the fourth photoresist film; Etching the etching stopper film on the semi-transmissive film using the phase shift film as a mask, and removing the etching stopper film excluding the boundary portion.
  • Such a photomask manufacturing method enables patterning of the semi-transmissive film and the phase shift film. Further, it is possible to arrange the semi-transmissive film pattern and the phase shift film pattern adjacent to each other. As a result, a photomask having both a halftone effect and a phase shift effect can be manufactured.
  • a multi-tone halftone mask capable of further miniaturizing a pattern and reducing a lithography process can be realized.
  • it is possible to contribute to a reduction in manufacturing cost of a high-quality flat panel display.
  • FIG. 5 is a comparative view of the inclination angle at the boundary between the photomask according to the first embodiment of the present invention and the photoresist film exposed by the conventional photomask.
  • Sectional drawing which shows the main processes of the photomask by the 2nd Embodiment of this invention.
  • Sectional drawing which shows the main processes of the photomask by the 2nd Embodiment of this invention.
  • Sectional drawing which shows the main processes of the photomask by the 2nd Embodiment of this invention.
  • Embodiment 1 (Embodiment 1)
  • Embodiment 1 of the halftone mask of the present invention will be described in detail.
  • a phase shift film 12 is formed on a transparent substrate 11 such as synthetic quartz glass by a sputtering method or the like, and an etching stopper film 13 is formed thereon by a sputtering method or the like.
  • a photomask blank 10 is prepared.
  • the phase shift film 12 has a phase shift angle of approximately 180 [degrees], inverts the phase of the exposure light, and the light transmittance of the phase shift film 12 with respect to the exposure light is 1% to 10%. If the light transmittance of the phase shift film 12 is too low, the effect of phase shift is reduced, so that the typical light transmittance is 5 to 7%.
  • a Cr (chromium) oxide film, a Cr oxynitride film or the like having a film thickness of 80 to 200 [nm] is used, and the film thickness and composition are adjusted in accordance with necessary characteristics.
  • a film in which the composition changes in the film thickness direction or a film in which films having different compositions are stacked may be used.
  • As exposure light g-line, h-line, i-line or a mixture of two or more of these can be used.
  • approximately 180 [degrees] is specifically in the range of 180 ⁇ 10 [degrees], and if it is within this range, the effect of phase inversion can be sufficiently obtained.
  • the etching stopper film 13 is made of a material different from the phase shift film 12 and having different etching characteristics.
  • a Ti (titanium) -based film Ti, Ti oxide film, Ti oxynitride film, or a laminated film thereof
  • Ni (nickel) A system film (Ni, Ni oxide film, Ni oxynitride film, or a laminated film thereof), a MoSi (molybdenum silicide) film, or the like is used.
  • a first photoresist film 14 is formed on the etching stopper film 13 by a coating method.
  • the first photoresist film 14 is exposed by, for example, a photomask drawing apparatus and then developed to form first photoresist patterns 14a, 14b, and 14c. .
  • the etching stopper film 13 is etched using the first photoresist patterns 14a, 14b, and 14c as masks to form etching stopper film patterns 13a, 13b, and 13c.
  • Etching can be performed by wet etching or dry etching.
  • the etchant has selectivity with respect to the phase shift film 12 (has etching resistance), and a chemical solution that can etch the etch stopper film 13 may be selected in accordance with the material of the etch stopper film 13.
  • a mixed solution of potassium hydroxide (KOH) and hydrogen peroxide water can be preferably used, but is not limited thereto.
  • the first photoresist patterns 14a, 14b, and 14c are removed by ashing or the like, and then the phase shift film 12 is formed using the etching stopper film patterns 13a, 13b, and 13c as a mask. Etching is performed to form phase shift film patterns 12a, 12b, and 12c.
  • a wet etching method or a dry etching method is used as an etching method for the phase shift film 12.
  • a wet etching method capable of obtaining a high etching selectivity can be suitably used.
  • a cerium-based etchant for example, nitric acid first solution is used as the phase shift film 12 etchant.
  • An aqueous solution of dicerium ammonium can be preferably used, but is not limited thereto.
  • the first photoresist pattern 14a may be removed by an ashing method or the like.
  • the etching process of the etching stopper film 13 and the etching process of the phase shift film 12 can be performed continuously.
  • a semi-transmissive film 15 such as Cr, Cr oxide film, Cr oxynitride film having a film thickness of 1 to 40 [nm] is formed as a halftone film by sputtering or the like.
  • a second photoresist film 16 is formed on the semi-transmissive film 15 by a coating method.
  • the light transmittance of the semi-transmissive film 15 is set to 10 to 60%, typically 20% to 55%.
  • the semi-transmissive film 15 does not reverse the phase of the exposure light, and the phase shift angle is, for example, 0.4 to 15 degrees.
  • the optical characteristics of the semi-transmissive film can be adjusted by the film thickness and composition.
  • the light transmittance of the semi-transmissive film which is a halftone film
  • the light transmittance of the semi-transmissive film is determined according to the purpose of use, customer specifications, and the like. Therefore, by preparing a photomask blank in which a phase shift film and an etching stopper film are laminated in advance and forming a halftone film according to the customer's specifications, manufacturing from photomask specification determination to photomask completion The construction period can be shortened.
  • the second photoresist film 16 is exposed and developed to form a second photoresist pattern 16a.
  • the semi-transmissive film 15 is etched using the second photoresist pattern 16a as a mask to form a semi-transmissive film pattern 15a, and then the second photo pattern is formed by ashing or the like.
  • the resist pattern 16a is removed.
  • a wet etching method or a dry etching method can be used as an etching method for the semi-transmissive film 15, but a wet etching method capable of obtaining a high etching selectivity can be preferably used.
  • an aqueous solution of ceric ammonium nitrate can be used as an etching solution.
  • the etching stopper film patterns 13a, 13b, and 13c on the phase shift film patterns 12a, 12b, and 12c are etched using the semi-transmissive film pattern 15a as a mask.
  • a part of the etching stopper film patterns 13d and 13e remain below the semi-transmissive film pattern 15a.
  • a wet etching method or a dry etching method can be used, but a wet etching method that can obtain a high etching selectivity can be preferably used.
  • a mixed solution of KOH and hydrogen peroxide water can be suitably used as the etching solution.
  • the semi-transmissive film 15 is etched using the second photoresist pattern 16a as a mask to form a semi-transmissive film pattern 15a, and an etching stopper on the phase shift film pattern 12a.
  • the second photoresist pattern 16a may be removed by ashing or the like.
  • phase shift film patterns 12a, 12b, and 12c, and a semi-transmissive film pattern 15a are formed on the photomask, and the transparent substrate 11 is exposed in the other regions.
  • the phase difference between the phase shift portion formed by the phase shift film patterns 12b and 12c and the semi-transmission portion formed by the semi-transmission film pattern 15a is approximately 180 [degrees].
  • the phase difference between the phase shift portion in the portion and the semi-transmissive portion formed by the pattern 15a of the semi-transmissive portion is 180- ⁇ when the phase shift angle of the semi-transmissive film is ⁇ [degrees].
  • the transmittance is 54%
  • the phase difference can be easily kept within a range of 180 ⁇ 10 [degrees] by fine adjustment of the thickness of the phase shift film 12 or the like. For this reason, the exposure light distribution also changes steeply at these boundary portions, and as a result, the profile of a photoresist formed on, for example, a flat panel substrate using the present photomask changes sharply at the boundary portions.
  • phase shift angle between the transparent portion where the substrate is exposed and the phase shift portion formed of the phase shift film is approximately 180 degrees, the profile of the photoresist formed by exposure is also steep at these boundaries. Become. As a result, it is possible to realize a photomask that can achieve both a halftone effect and a phase shift effect.
  • the etching stopper film patterns 13d and 13e remain at the boundary portion where the phase shift portion and the semi-transmissive portion are adjacent to each other.
  • the width of the etching stopper film patterns 13d and 13e remaining at the boundary portion is an amount corresponding to an alignment error (alignment deviation) of a photomask drawing apparatus (laser drawing apparatus) for exposing the second photoresist pattern 16a. It is.
  • the semi-transmissive portion and the phase shift portion are overlapped and can be adjacent to each other without generating a gap.
  • the widths of the etching stopper film patterns 13d and 13e are set to dimensions that do not affect the exposure result when the photoresist is exposed by the photomask pattern. That is, the widths of the etching stopper film patterns 13d and 13e are set to be equal to or less than the resolution limit of a projection exposure apparatus that exposes the photoresist using a photomask.
  • the value of the resolution limit of the projection exposure apparatus is expressed by the following equation ⁇ / (2NA) Can be used.
  • ⁇ is the wavelength (representative wavelength) of the projection exposure apparatus
  • NA is the numerical aperture of the projection exposure apparatus.
  • the actual widths of 13d and 13e in the produced photomask are set by setting the widths (set values) of the boundary portions 13d and 13e as the alignment error d [ ⁇ m] of the photomask drawing apparatus.
  • the (actual measured value) falls within the range of 0 to 2d.
  • a typical value of d of the laser drawing apparatus is, for example, 0.5 [ ⁇ m]
  • the actual width of the boundary portion in the photomask is 0 to 1 [ ⁇ m].
  • the NA is about 0.09 and the representative wavelength ⁇ is 365 [nm]. When these values are applied to the above equation, the resolution limit value is 2.0 [ ⁇ m].
  • the alignment error of the laser drawing apparatus is sufficiently small. Therefore, by setting the widths of the etching stopper film patterns 13d and 13e to the alignment error of the photomask drawing apparatus, the actual conditions will be less than the resolution limit of the photoresist projection exposure apparatus. It is possible to achieve both.
  • the phase shift film patterns 12b and 12c can be used for TFT source / drain electrodes, and the semi-transmissive film pattern 15a can be used for pattern formation of the TFT channel region. Since the profile of the photoresist film at the boundary between the source / drain region and the channel region becomes steep, and the edge portion of the source / drain electrode also becomes steep, miniaturization of the TFT can be realized.
  • FIG. 4 shows a photo exposed by a conventional photomask in which the shape of the photoresist exposed by this embodiment combining a halftone film and a phase shift film and a halftone film and a light-shielding film that does not transmit exposure light are combined. A comparison with the resist shape is shown.
  • FIG. 4A is a cross-sectional view of the photomask of the present embodiment
  • FIG. 4A is an enlarged view of a part of FIG.
  • FIG. 4B is a part of a cross section of a conventional photomask disclosed in Patent Document 1, in which a halftone film pattern 43 is formed on a transparent substrate 42, and a barrier is formed on the halftone film pattern 43.
  • a film (etching stopper film) pattern 44 and a light shielding film pattern 45 are formed.
  • FIG. 4C schematically shows a cross-sectional shape of the photoresist 30 exposed by the photomask shown in FIG.
  • the photoresist film thickness at the portion corresponding to the semi-transmissive film, which is a halftone film, is thinner than the photoresist film thickness at the position corresponding to the phase shift film, and different photoresist film thicknesses by one exposure with one photomask.
  • a point P indicated by a black circle indicates a portion corresponding to the boundary between the semi-transmissive film that is a halftone film and the phase shift film.
  • a photoresist 40 having different film thicknesses can be formed by one exposure, and FIG. 4D is exposed by the photomask shown in FIG.
  • the cross-sectional shape of the photoresist 40 is schematically shown.
  • a point Q indicated by a black circle in FIG. 4D indicates a portion corresponding to the boundary between the halftone film and the light shielding film.
  • FIG. 4E is a graph showing the inclination angles of the photoresists 30 and 40 at points P and Q in comparison.
  • the inclination angle of the point P of the photomask according to the present embodiment is larger than the inclination angle of the point Q of the conventional photomask, and the cross-sectional shape of the boundary portion of the photoresist 30 is larger. It can be understood that it becomes steep. That is, in comparison with the case where the photoresist is exposed by the conventional photomask, the photoresist film is improved by exposing the photoresist by the photomask according to the present embodiment, and in the boundary region where the resist film thickness changes. A steep cross-sectional shape can be obtained.
  • Embodiment 2 In Embodiment 1 above, the semi-transmissive film is formed after the phase shift film is formed on the transparent substrate. However, the photomask is manufactured by forming the semi-transmissive film on the transparent substrate and then forming the phase shift film. May be. Hereinafter, a photomask manufacturing method will be described with reference to the drawings. However, as the transparent substrate, the phase shift film, the semi-transmissive film, and the etching stopper film, films similar to those in Embodiment 1 can be used.
  • a semi-transmissive film 22 is formed as a halftone film on a transparent substrate 21 such as synthetic quartz glass by a sputtering method or the like, and an etching stopper film 23 is formed thereon by a sputtering method or the like.
  • the photomask blanks 20 are prepared by forming a film by the above.
  • a third photoresist film 24 is formed on the etching stopper film 23 by a coating method.
  • the third photoresist film 24 is exposed and developed to form a third photoresist pattern 24a.
  • the etching stopper film 23 is etched using the third photoresist pattern 24a as a mask to form an etching stopper film pattern 23a.
  • the third photoresist pattern 24a is removed by ashing or the like, and then the semi-transmissive film 22 is etched using the pattern 23a of the etching stopper film as a mask. 22a is formed.
  • the semi-transmissive film 22 may be etched to form the semi-transmissive film pattern 22a, and then the third photoresist pattern 24a may be removed by an ashing method or the like.
  • the etching step of the etching stopper film 23 and the etching step of the semi-transmissive film 22 can be performed continuously, and a high etching selectivity with respect to the semi-transmissive film 22 is not necessarily ensured in the etching step of the etching stopper film 23. There is no need.
  • etching the semi-transmissive film 22 using the pattern 23a of the etching stopper film as a mask is effective in suppressing side etching of both films.
  • a phase shift film 25 is formed by a sputtering method or the like, and then a fourth photoresist film 26 is formed on the phase shift film 25 by a coating method.
  • the fourth photoresist film 26 is exposed and developed to form fourth photoresist patterns 26a, 26b, and 26c.
  • phase shift film 25 is etched using the fourth photoresist patterns 26a, 26b, and 26c as masks to form phase shift film patterns 25a, 25b, and 25c. Thereafter, the fourth photoresist patterns 26a, 26b, and 26c are removed by ashing or the like.
  • the pattern 23a of the etching stopper film on the pattern 22a of the semi-transmissive film is etched using the patterns 25a and 25b of the phase shift film as a mask.
  • the phase shift film 25 is etched using the fourth photoresist pattern 26a as a mask to form phase shift film patterns 25a, 25b, and 25c, and a semi-transmissive film pattern 22a.
  • the fourth photoresist pattern 26a may be removed by ashing or the like.
  • the phase difference between the phase shift part formed by the phase shift film patterns 25a and 25b and the semi-transmission part of the semi-transmission film pattern 22a is 180 when the phase shift angle of the semi-transmission film is ⁇ [degrees].
  • the phase difference can be easily kept within a range of 180 ⁇ 10 [degrees] by fine adjustment of the thickness of the phase shift film 12 or the like.
  • the exposure light distribution changes steeply even in this boundary portion, and as a result, the profile of a photoresist formed on, for example, a flat panel substrate using this photomask changes sharply in the corresponding boundary portion.
  • the phase difference between the phase shift portion and the transparent portion where the substrate is exposed is also approximately 180 degrees, the exposure light distribution at the boundary portion changes abruptly, and a photoresist formed using this photomask.
  • the profile can be a steep shape at the corresponding boundary portion.
  • the present invention can provide a photomask capable of realizing a reduction in photolithography process and miniaturization of a pattern, and its industrial applicability is extremely large.
  • Photomask blank 11 Transparent substrate 12 Phase shift film 12a, 12b, 12c Phase shift film pattern 13 Etching stopper film 13a, 13b, 13c, 13d, 13e Etching stopper film pattern 14 First photoresist film 14a, 14b, 14c First photoresist pattern 15 Semi-transmissive film 15a Semi-transmissive film pattern 16 Second photoresist film 16a Second photoresist pattern 20 Photomask blanks 21 Transparent substrate 22 Semi-transmissive film 22a Semi-transmissive film pattern 23 Etching Stopper film 23a Etching stopper film pattern 24 Third photoresist film 25 Phase shift film 25a, 25b, 25c Phase shift film pattern 26 Fourth photoresist film 26a, 26b, 26c Fourth photoresist Pattern of turns 30 photoresist 40 photoresist 42 transparent substrate 43 pattern 45 light-shielding film pattern 44 barrier film of the halftone film

Abstract

[Problem] To provide a multi-gray level halftone mask which enables the exposure of a fine photoresist pattern. [Solution] On a transparent substrate, a semi-transmitting part comprising a pattern of a semi-transmitting film and a phase shift part comprising a pattern of a phase shift film are formed, wherein the phase shift film inverts the phase of exposing light, and the transmittance of the phase shift film is lower than that of the semi-transmitting film. In addition, on a boundary part to which the semi-transmitting part and the phase shift part are adjacent, a laminated film of the semi-transmitting film, the phase shift film, and an etching stopper film is formed, wherein the etching stopper film comprises a material which is not etched by an etchant for the semi-transmitting film and an etchant for the phase shift film. Consequently, a photomask having both a halftone effect and a phase shift effect is obtained.

Description

ハーフトーンマスク、フォトマスクブランクス及びハーフトーンマスクの製造方法Halftone mask, photomask blank, and method of manufacturing halftone mask
　本発明は、フラットパネルディスプレイ等に使用される多階調のフォトマスクであるハーフトーンマスク、フォトマスクブランクス及びハーフトーンマスクの製造方法に関する。 The present invention relates to a halftone mask, a photomask blank, and a halftone mask manufacturing method, which are multi-tone photomasks used for flat panel displays and the like.
　フラットパネルディスプレイなどの技術分野においては、半透過膜の透過率で露光量を制限するという機能を備えた、ハーフトーンマスクと呼ばれる多階調のフォトマスクが使用されている。
　ハーフトーンマスクは、透明基板と遮光膜との中間の透過率を有する半透過膜を利用し、透明基板、半透過膜、遮光膜により、３階調又はそれ以上の多階調のフォトマスクを実現することができる。 In a technical field such as a flat panel display, a multi-tone photomask called a halftone mask having a function of limiting an exposure amount by the transmittance of a semi-transmissive film is used.
The halftone mask uses a transflective film having an intermediate transmittance between the transparent substrate and the light shielding film, and a multi-tone photomask having three or more gradations is formed by the transparent substrate, the semitransmissive film, and the light shielding film. Can be realized.
　特許文献１に開示されるようなハーフトーンマスクを使用することにより、１回の露光で膜厚の異なるフォトレジストパターンを形成することができ、フラットパネルディスプレイの製造工程におけるリソグラフィーの工程数を削減し、製造コストを低減することが可能となる。
　例えば、薄膜トランジスタ（ＴＦＴ）を用いた液晶表示装置においては、ＴＦＴのチャネル領域及びソース／ドレイン電極形成領域で、それぞれ膜厚の異なるフォトレジストパターンを１回の露光工程で形成することで、リソグラフィー工程を削減し、それにより製造コストを削減する技術がとして用いられる。 By using a halftone mask as disclosed in Patent Document 1, photoresist patterns having different film thicknesses can be formed by a single exposure, and the number of lithography processes in the flat panel display manufacturing process can be reduced. In addition, manufacturing costs can be reduced.
For example, in a liquid crystal display device using a thin film transistor (TFT), a lithography process is performed by forming photoresist patterns having different film thicknesses in a single exposure process in the channel region and source / drain electrode formation region of the TFT. As a technique, the manufacturing cost is thereby reduced.
　一方で、フラットパネルディスプレイの高画質化のため、配線パターンの微細化の要望が、ますます強くなってきている。プロジェクション露光機で、解像限界に近いパターンを露光しようとする場合、露光マージンを確保するため、特許文献２に開示されるように、遮光領域のエッジ部に位相を反転させる位相シフタを設けた位相シフトマスクが提案されている。 On the other hand, in order to improve the image quality of flat panel displays, the demand for finer wiring patterns has become stronger. When a projection exposure machine tries to expose a pattern close to the resolution limit, a phase shifter for inverting the phase is provided at the edge of the light shielding area as disclosed in Patent Document 2 in order to secure an exposure margin. A phase shift mask has been proposed.
特開２０１１－２２７３９１JP2011-227391 特開２０１１－１３２８３JP2011-13283A
　ハーフトーンマスクは、リソグラフィー工程の削減に寄与することはできるものの、半透過膜と遮光膜との境界における露光光の強度分布の変化が比較的緩やかであり、そのためハーフトーンマスクを用いて露光したフォトレジスト膜は、境界に相当する部分での断面形状が緩やかな傾斜を示し、プロセスマージンが低下し、微細なパターンを形成することが困難であるという問題がある。 Although the halftone mask can contribute to the reduction of the lithography process, the change in the intensity distribution of the exposure light at the boundary between the semi-transmissive film and the light-shielding film is relatively gradual, so that exposure is performed using the half-tone mask. The photoresist film has a problem that the cross-sectional shape at the portion corresponding to the boundary shows a gentle inclination, the process margin is lowered, and it is difficult to form a fine pattern.
　位相シフトマスクを使用することにより解像度が向上し、パターンの更なる微細化が可能となる。しかし、位相シフトマスクはバイナリマスクを対象とする技術であるため、ハーフトーンマスクの様なリソグラフィー工程の削減は不可能である。そのため、フラットパネルディスプレイの製造に使用した場合、リソグラフィー工程の削減に寄与することができない。 The resolution is improved by using the phase shift mask, and the pattern can be further miniaturized. However, since the phase shift mask is a technique for a binary mask, it is impossible to reduce the lithography process like a halftone mask. Therefore, when used for manufacturing a flat panel display, it cannot contribute to the reduction of the lithography process.
　このように従来のフォトマスクでは、フラットパネルディスプレイ製造コストの低減と解像度の問題を両立させることは不可能であった。 Thus, with the conventional photomask, it was impossible to achieve both the reduction of the flat panel display manufacturing cost and the resolution problem.
　上記課題を鑑み、本発明は、リソグラフィー工程の削減とパターンの更なる微細化を両立することができるフォトマスク及びその製造に使用するフォトマスクブランクス、ならびにフォトマスクの製造方法を提供することを目的とする。 In view of the above problems, an object of the present invention is to provide a photomask, a photomask blank used for manufacturing the photomask, and a method for manufacturing the photomask that can achieve both reduction of the lithography process and further miniaturization of the pattern. And
　本発明の実施形態にかかるフォトマスクは、
　透明基板上に半透過部、位相シフト部、境界部及び透光部を有し、
　前記透光部は、前記透明基板が露出した部分からなり、
　前記半透過部は、前記透明基板上に設けられた半透過膜で形成され、
　前記位相シフト部は前記透明基板上に設けられた位相シフト膜で形成され、
　前記境界部は、前記半透過部と前記位相シフト部とが隣接する領域に形成され、
　前記境界部の幅が一定幅以下であり、
　前記境界部は、前記位相シフト膜、エッチングストッパ膜、前記半透過膜がこの順に形成された積層構造膜で形成される一方、前記境界部を除く前記半透過部、前記位相シフト部及び前記透光部の前記エッチングストッパ膜は除去され、
　前記境界部の幅は、前記フォトマスクが用いられる投影露光装置の解像限界以下である
　ことを特徴とする。 The photomask according to the embodiment of the present invention is
Having a transflective part, a phase shift part, a boundary part and a translucent part on a transparent substrate;
The translucent part consists of a portion where the transparent substrate is exposed,
The semi-transmissive portion is formed of a semi-transmissive film provided on the transparent substrate,
The phase shift part is formed of a phase shift film provided on the transparent substrate,
The boundary portion is formed in a region where the semi-transmissive portion and the phase shift portion are adjacent to each other,
The width of the boundary is not more than a certain width;
The boundary portion is formed of a laminated structure film in which the phase shift film, the etching stopper film, and the semi-transmissive film are formed in this order, while the semi-transmissive portion, the phase shift portion, and the transparent portion excluding the boundary portion. The etching stopper film of the optical part is removed,
The width of the boundary portion is not more than a resolution limit of a projection exposure apparatus in which the photomask is used.
　また、本発明の実施形態にかかるフォトマスクは、
　透明基板に半透過部、位相シフト部、境界部及び透光部を有し、
　前記透光部は前記透明基板が露出した部分からなり、
　前記半透過部は前記透明基板上に設けられた半透過膜で形成され、
　前記位相シフト部は前記透明基板上に設けられた位相シフト膜で形成され、
　前記境界部は、前記半透過部と前記位相シフト部とが隣接する領域に形成され、
　前記境界部の幅が一定幅以下であり、
　前記境界部は、前記半透過膜、エッチングストッパ膜、前記位相シフト膜がこの順に形成される一方、前記境界部を除く前記半透過部、前記位相シフト部及び前記透光部の前記エッチングストッパ膜は除去され、
　前記境界部の幅は、前記フォトマスクが用いられる投影露光装置の解像限界以下である
　ことを特徴とする。 In addition, the photomask according to the embodiment of the present invention is
A transparent substrate has a semi-transmissive part, a phase shift part, a boundary part, and a translucent part,
The translucent part consists of a portion where the transparent substrate is exposed,
The semi-transmissive part is formed of a semi-permeable film provided on the transparent substrate,
The phase shift part is formed of a phase shift film provided on the transparent substrate,
The boundary portion is formed in a region where the semi-transmissive portion and the phase shift portion are adjacent to each other,
The width of the boundary is not more than a certain width;
In the boundary portion, the semi-transmissive film, the etching stopper film, and the phase shift film are formed in this order, while the semi-transmissive portion, the phase shift portion, and the light transmitting portion except for the boundary portion are etched stopper films. Is removed,
The width of the boundary portion is not more than a resolution limit of a projection exposure apparatus in which the photomask is used.
　本発明の実施形態にかかるフォトマスクは、
　前記位相シフト膜は、露光光に対する透過率が１～１０［％］であり、かつ露光光の位相が反転することを特徴とする請求項１又は２記載のフォトマスク。 The photomask according to the embodiment of the present invention is
3. The photomask according to claim 1, wherein the phase shift film has a transmittance with respect to exposure light of 1 to 10%, and the phase of the exposure light is reversed.
　本発明の実施形態にかかるフォトマスクは、
　前記半透過膜の露光光に対する透過率は１０～６０［％］であることを特徴とする。 The photomask according to the embodiment of the present invention is
The translucent film has a transmittance with respect to exposure light of 10 to 60%.
　このような構成とすることで、半透過部は、位相シフト部及び透光部の中間の光透過率であり、半透過部、位相シフト部及び透光部によって多階調のフォトマスクを得ることができる。さらに半透過部と位相シフト部とを隣接させることで、半透過部と位相シフト部との境界部での露光光のプロファイルを急峻に変化させることができ、露光されたフォトレジストの形状を改善し、パターンの微細化を実現することができる。その結果、ハーフトーン効果と位相シフトの効果の両方を有するフォトマスクを得ることができる。 With such a configuration, the transflective portion has a light transmittance intermediate between the phase shift portion and the translucent portion, and a multi-tone photomask is obtained by the transflective portion, the phase shift portion, and the translucent portion. be able to. Furthermore, by making the semi-transmission part and the phase shift part adjacent to each other, the profile of the exposure light at the boundary between the semi-transmission part and the phase shift part can be changed sharply, improving the shape of the exposed photoresist. In addition, pattern miniaturization can be realized. As a result, a photomask having both a halftone effect and a phase shift effect can be obtained.
　本発明の実施形態にかかるフォトマスクは、
　前記位相シフト膜と前記半透過膜とは、同じエッチング液によりエッチング可能であり、前記エッチングストッパ膜は、前記エッチング液に対してエッチング選択性を有することを特徴とする。
　具体的には、例えば、前記エッチングストッパ膜はＴｉ系膜で構成され、前記位相シフト膜はＣｒ酸化膜で構成される。 The photomask according to the embodiment of the present invention is
The phase shift film and the semi-transmissive film can be etched with the same etching solution, and the etching stopper film has an etching selectivity with respect to the etching solution.
Specifically, for example, the etching stopper film is made of a Ti-based film, and the phase shift film is made of a Cr oxide film.
　このような構成とすることで、フォトマスクの製造工程において、ウェットエッチングを用いて、フォトマスクの製造が容易になる。 With such a configuration, the photomask can be easily manufactured using wet etching in the photomask manufacturing process.
　本発明の実施形態にかかるフォトマスクは、
　前記境界部の幅は、フォトマスク描画装置の位置合わせ誤差に設定され、前記フォトマスクが用いられる投影露光装置の解像限界以下であることを特徴とする。 The photomask according to the embodiment of the present invention is
The width of the boundary portion is set to an alignment error of a photomask drawing apparatus and is equal to or less than a resolution limit of a projection exposure apparatus in which the photomask is used.
　このような構成とすることで、境界部分のエッチングストッパ膜がフォトレジストの露光に対して悪影響を与えること無く、半透過部と位相シフト部とを隣接させることが可能となる。 With such a configuration, the semi-transmissive portion and the phase shift portion can be adjacent to each other without the etching stopper film at the boundary portion having an adverse effect on the exposure of the photoresist.
　本発明の実施形態にかかるフォトマスクブランクスは、
　前記フォトマスクを製造するためのフォトマスクブランクスであって、
前記透明基板上に前記位相シフト膜及び前記エッチングストッパ膜が、この順に積層されたことを特徴とする。 The photomask blank according to the embodiment of the present invention is
Photomask blanks for manufacturing the photomask,
The phase shift film and the etching stopper film are laminated in this order on the transparent substrate.
　このような構成のフォトマスクブランクスとすることにより、フォトマスクブランクス上に顧客の仕様や用途に合わせた半透過膜を成膜し、多階調マスクを形成することができる。その結果、ハーフトーン効果と位相シフトの効果の両方を備えた、所望の特性を有するフォトマスクの製造工期を短縮することができる。 By using a photomask blank having such a structure, a multi-tone mask can be formed on a photomask blank by forming a transflective film according to customer specifications and applications. As a result, it is possible to shorten the manufacturing period of a photomask having desired characteristics having both a halftone effect and a phase shift effect.
　本発明の実施形態にかかるフォトマスクの製造方法は、
透明基板上に位相シフト膜及びエッチングストッパ膜をこの順に積層する工程と、
　第１のフォトレジスト膜を形成する工程と、
　前記第１のフォトレジスト膜をパターニングする工程と、
　前記第１のフォトレジスト膜をマスクに前記エッチングストッパ膜をエッチングする工程と、
　前記エッチングストッパ膜をマスクに前記位相シフト膜をエッチングする工程と、
　前記第１のフォトレジスト膜を除去する工程と、
　半透過膜を形成する工程と、
　第２のフォトレジスト膜を形成する工程と、
　エッチングされた前記エッチングストッパ膜と前記投影露光装置の解像限界以下の幅の重なりを有するよう前記第２のフォトレジスト膜をパターニングする工程と、
　前記第２のフォトレジスト膜をマスクに前記半透過膜をエッチングする工程と、
　前記第２のフォトレジスト膜を除去する工程と、
　前記半透過膜をマスクに前記位相シフト膜上の前記エッチングストッパ膜をエッチングし、前記境界部を除く前記エッチングストッパ膜を除去する工程と
を含むことを特徴とする。 A photomask manufacturing method according to an embodiment of the present invention includes:
A step of laminating a phase shift film and an etching stopper film in this order on a transparent substrate;
Forming a first photoresist film;
Patterning the first photoresist film;
Etching the etching stopper film using the first photoresist film as a mask;
Etching the phase shift film using the etching stopper film as a mask;
Removing the first photoresist film;
Forming a semipermeable membrane;
Forming a second photoresist film;
Patterning the second photoresist film so as to have an overlap of the etched stopper film and the width below the resolution limit of the projection exposure apparatus;
Etching the semi-transmissive film using the second photoresist film as a mask;
Removing the second photoresist film;
Etching the etching stopper film on the phase shift film using the semi-transmissive film as a mask, and removing the etching stopper film excluding the boundary portion.
　また、本発明の実施形態にかかるフォトマスクの製造方法は、
　透明基板上に半透過膜及びエッチングストッパ膜をこの順に積層する工程と、
　第３のフォトレジスト膜を形成する工程と、
　前記第３のフォトレジスト膜をパターニングする工程と、
　前記第３のフォトレジスト膜をマスクに前記エッチングストッパ膜をエッチングする
工程と、
　前記エッチングストッパ膜をマスクに前記半透過膜をエッチングする工程と、
　前記第３のフォトレジスト膜を除去する工程と、
　位相シフト膜を形成する工程と、
　第４のフォトレジスト膜を形成する工程と、
　エッチングされた前記エッチングストッパ膜と前記投影露光装置の解像限界以下の幅の重なりを有するよう前記第４のフォトレジスト膜をパターニングする工程と、
　前記第４のフォトレジスト膜をマスクに前記位相シフト膜をエッチングする工程と、
　前記第４のフォトレジスト膜を除去する工程と、
　前記位相シフト膜をマスクに前記半透過膜上の前記エッチングストッパ膜をエッチングし、前記境界部を除く前記エッチングストッパ膜を除去する工程と
を含むことを特徴とする。 In addition, a photomask manufacturing method according to an embodiment of the present invention includes:
A step of laminating a semi-transmissive film and an etching stopper film in this order on a transparent substrate;
Forming a third photoresist film;
Patterning the third photoresist film;
Etching the etching stopper film using the third photoresist film as a mask;
Etching the semi-transmissive film using the etching stopper film as a mask;
Removing the third photoresist film;
Forming a phase shift film;
Forming a fourth photoresist film;
Patterning the fourth photoresist film so as to have an overlap of the etched stopper film and the width below the resolution limit of the projection exposure apparatus;
Etching the phase shift film using the fourth photoresist film as a mask;
Removing the fourth photoresist film;
Etching the etching stopper film on the semi-transmissive film using the phase shift film as a mask, and removing the etching stopper film excluding the boundary portion.
　このようなフォトマスクの製造方法により、半透過膜と位相シフト膜のパターニングが可能となる。さらに半透過膜のパターンと位相シフト膜のパターンとを隣接して配置することも可能となる。その結果、ハーフトーンの効果と位相シフトの効果の両方を有するフォトマスクを製造することができる。 Such a photomask manufacturing method enables patterning of the semi-transmissive film and the phase shift film. Further, it is possible to arrange the semi-transmissive film pattern and the phase shift film pattern adjacent to each other. As a result, a photomask having both a halftone effect and a phase shift effect can be manufactured.
　本発明によれば、パターンの更なる微細化とリソグラフィー工程の削減が可能な多階調のハーフトーンマスクを実現することができる。その結果、例えば高画質なフラットパネルディスプレの製造コストの低減に寄与することができる。 According to the present invention, a multi-tone halftone mask capable of further miniaturizing a pattern and reducing a lithography process can be realized. As a result, for example, it is possible to contribute to a reduction in manufacturing cost of a high-quality flat panel display.
本発明の第１の実施形態によるフォトマスクの主要工程を示す断面図。Sectional drawing which shows the main processes of the photomask by the 1st Embodiment of this invention. 本発明の第１の実施形態によるフォトマスクの主要工程を示す断面図。Sectional drawing which shows the main processes of the photomask by the 1st Embodiment of this invention. 本発明の第１の実施形態によるフォトマスクの主要工程を示す断面図。Sectional drawing which shows the main processes of the photomask by the 1st Embodiment of this invention. 本発明の第１の実施形態によるフォトマスクと従来のフォトマスクにより露光されたフォトレジスト膜の境界部における傾斜角度の比較図。FIG. 5 is a comparative view of the inclination angle at the boundary between the photomask according to the first embodiment of the present invention and the photoresist film exposed by the conventional photomask. 本発明の第２の実施形態によるフォトマスクの主要工程を示す断面図。Sectional drawing which shows the main processes of the photomask by the 2nd Embodiment of this invention. 本発明の第２の実施形態によるフォトマスクの主要工程を示す断面図。Sectional drawing which shows the main processes of the photomask by the 2nd Embodiment of this invention. 本発明の第２の実施形態によるフォトマスクの主要工程を示す断面図。Sectional drawing which shows the main processes of the photomask by the 2nd Embodiment of this invention.
　　以下、図面を参照して本発明の実施形態について説明する。但し、以下の実施形態は、いずれも本発明の要旨の認定において限定的な解釈を与えるものではない。また、同一又は同種の部材については同じ参照符号を付して、説明を省略することがある。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, none of the following embodiments gives a limited interpretation in the recognition of the gist of the present invention. The same or similar members are denoted by the same reference numerals, and the description thereof may be omitted.
（実施形態１）
　以下、本発明のハーフトーンマスクの実施形態１の製造工程を詳細に説明する。 (Embodiment 1)
Hereinafter, the manufacturing process of Embodiment 1 of the halftone mask of the present invention will be described in detail.
　図１（Ａ）に示すように、合成石英ガラス等の透明基板１１上に、位相シフト膜１２をスパッタ法等により成膜し、その上にエッチングストッパ膜１３をスパッタ法等により成膜することにより、フォトマスクブランクス１０を準備する。 As shown in FIG. 1A, a phase shift film 12 is formed on a transparent substrate 11 such as synthetic quartz glass by a sputtering method or the like, and an etching stopper film 13 is formed thereon by a sputtering method or the like. Thus, a photomask blank 10 is prepared.
　位相シフト膜１２は、その位相シフト角は略１８０［度］であり、露光光の位相を反転し、露光光に対する位相シフト膜１２の光透過率は１％～１０％である。
　位相シフト膜１２の光透過率が低すぎると位相シフトの効果が小さくなるため、典型的な光透過率は５～７［％］である。具体的には、例えば膜厚８０～２００［ｎｍ］のＣｒ（クロム）酸化膜、Ｃｒ酸窒化膜等を使用し、必要な特性に合わせて膜厚や組成を調整する。また、必ずしも単層膜である必要はなく、例えば膜厚方向に対して組成が変化する膜や、組成が異なる膜を積層した膜であってもよい。
　なお、露光光として、ｇ線、ｈ線、ｉ線やこれらの２つ以上の混合光を用いることができる。
　　ここで略１８０［度］とは、具体的には、１８０±１０［度］の範囲であり、この範囲であれば位相反転の効果を十分に得ることができる。 The phase shift film 12 has a phase shift angle of approximately 180 [degrees], inverts the phase of the exposure light, and the light transmittance of the phase shift film 12 with respect to the exposure light is 1% to 10%.
If the light transmittance of the phase shift film 12 is too low, the effect of phase shift is reduced, so that the typical light transmittance is 5 to 7%. Specifically, for example, a Cr (chromium) oxide film, a Cr oxynitride film or the like having a film thickness of 80 to 200 [nm] is used, and the film thickness and composition are adjusted in accordance with necessary characteristics. Further, it is not necessarily a single layer film, and for example, a film in which the composition changes in the film thickness direction or a film in which films having different compositions are stacked may be used.
As exposure light, g-line, h-line, i-line or a mixture of two or more of these can be used.
Here, approximately 180 [degrees] is specifically in the range of 180 ± 10 [degrees], and if it is within this range, the effect of phase inversion can be sufficiently obtained.
　エッチングストッパ膜１３は、位相シフト膜１２とは材質が異なり、エッチング特性の異なる膜を使用する。具体的には、エッチングストッパ膜１３として、例えば膜厚４～３０［ｎｍ］のＴｉ（チタン）系膜（Ｔｉ、Ｔｉ酸化膜、Ｔｉ酸窒化膜、若しくはこれらの積層膜）、Ｎｉ（ニッケル）系膜（Ｎｉ、Ｎｉ酸化膜、Ｎｉ酸窒化膜、若しくはこれらの積層膜）、ＭｏＳｉ（モリブデンシリサイド）膜等を使用する。 The etching stopper film 13 is made of a material different from the phase shift film 12 and having different etching characteristics. Specifically, as the etching stopper film 13, for example, a Ti (titanium) -based film (Ti, Ti oxide film, Ti oxynitride film, or a laminated film thereof) having a film thickness of 4 to 30 [nm], Ni (nickel) A system film (Ni, Ni oxide film, Ni oxynitride film, or a laminated film thereof), a MoSi (molybdenum silicide) film, or the like is used.
　次に、エッチングストッパ膜１３上に第１のフォトレジスト膜１４を塗布法により形成する。 Next, a first photoresist film 14 is formed on the etching stopper film 13 by a coating method.
　次に図１（Ｂ）に示すように、第１のフォトレジスト膜１４を、例えばフォトマスク描画装置により露光し、その後現像することにより、第１のフォトレジストパターン１４ａ、１４ｂ、１４ｃを形成する。 Next, as shown in FIG. 1B, the first photoresist film 14 is exposed by, for example, a photomask drawing apparatus and then developed to form first photoresist patterns 14a, 14b, and 14c. .
　次に図１（Ｃ）に示すように、第１のフォトレジストパターン１４ａ、１４ｂ、１４ｃをマスクにエッチングストッパ膜１３をエッチングし、エッチングストッパ膜のパターン１３ａ、１３ｂ、１３ｃを形成する。
　エッチングはウェットエッチング法又はドライエッチング法により行うことができる。位相シフト膜１２に対して選択的にエッチングストッパ膜１３をエッチングする場合、好適には高い選択比を有するウェットエッチングが使用できる。エッチング液は、位相シフト膜１２に対して選択性を有し（エッチング耐性があり）、エッチングストッパ膜１３の材質に合わせて、エッチングストッパ膜１３をエッチングできる薬液を選択すればよい。例えばＴｉ系膜を使用する場合、水酸化カリウム（ＫＯＨ）と過酸化水素水の混合液を好適に使用できるが、これに限るものではない。 Next, as shown in FIG. 1C, the etching stopper film 13 is etched using the first photoresist patterns 14a, 14b, and 14c as masks to form etching stopper film patterns 13a, 13b, and 13c.
Etching can be performed by wet etching or dry etching. When the etching stopper film 13 is selectively etched with respect to the phase shift film 12, it is preferable to use wet etching having a high selection ratio. The etchant has selectivity with respect to the phase shift film 12 (has etching resistance), and a chemical solution that can etch the etch stopper film 13 may be selected in accordance with the material of the etch stopper film 13. For example, in the case of using a Ti-based film, a mixed solution of potassium hydroxide (KOH) and hydrogen peroxide water can be preferably used, but is not limited thereto.
　次に図２（Ａ）に示すように、第１のフォトレジストパターン１４ａ、１４ｂ、１４ｃをアッシング等により除去し、その後、エッチングストッパ膜のパターン１３ａ、１３ｂ、１３ｃをマスクに位相シフト膜１２をエッチングし、位相シフト膜のパターン１２ａ、１２ｂ、１２ｃを形成する。
　位相シフト膜１２のエッチング法として、ウェットエッチング法又はドライエッチング法が用いられる。ただし、エッチングストッパ膜に対して位相シフト膜１２を選択的にエッチングするため、高いエッチング選択比が得られるウェットエッチング法が好適に使用できる。
　例えば、上記のようにエッチングストッパ膜１３をＴｉ系膜、位相シフト膜１２をＣｒ酸化膜、Ｃｒ酸窒化膜とすると、位相シフト膜１２のエッチング液として、セリウム系のエッチング液である例えば硝酸第二セリウムアンモニウム水溶液を好適に使用することができるが、これに限定するものではない。 Next, as shown in FIG. 2A, the first photoresist patterns 14a, 14b, and 14c are removed by ashing or the like, and then the phase shift film 12 is formed using the etching stopper film patterns 13a, 13b, and 13c as a mask. Etching is performed to form phase shift film patterns 12a, 12b, and 12c.
As an etching method for the phase shift film 12, a wet etching method or a dry etching method is used. However, since the phase shift film 12 is selectively etched with respect to the etching stopper film, a wet etching method capable of obtaining a high etching selectivity can be suitably used.
For example, when the etching stopper film 13 is a Ti-based film and the phase shift film 12 is a Cr oxide film and a Cr oxynitride film as described above, a cerium-based etchant, for example, nitric acid first solution is used as the phase shift film 12 etchant. An aqueous solution of dicerium ammonium can be preferably used, but is not limited thereto.
　また、位相シフト膜１２をエッチングし、位相シフト膜のパターン１２ａ、１２ｂ、１２ｃを形成した後に、アッシング法等により第１のフォトレジストパターン１４ａを除去してもよい。
　この場合、エッチングストッパ膜１３のエッチング工程と位相シフト膜１２のエッチング工程を連続して行うこともできる。 Alternatively, after the phase shift film 12 is etched to form the phase shift film patterns 12a, 12b, and 12c, the first photoresist pattern 14a may be removed by an ashing method or the like.
In this case, the etching process of the etching stopper film 13 and the etching process of the phase shift film 12 can be performed continuously.
　次に、図２（Ｂ）に示すように、ハーフトーン膜として、例えば膜厚１～４０［ｎｍ］のＣｒ、Ｃｒ酸化膜、Ｃｒ酸窒化膜等の半透過膜１５、をスパッタ法等により形成し、その後、半透過膜１５上に第２のフォトレジスト膜１６を塗布法により形成する。
　ここで、上記半透過膜１５の光透過率は、１０～６０％、典型的には２０％～５５％に設定する。半透過膜１５は露光光の位相を反転せず、位相シフト角は、例えば０．４～１５度である。半透過膜の上記光学的特性は、膜厚や組成によって調整することができる。 Next, as shown in FIG. 2B, for example, a semi-transmissive film 15 such as Cr, Cr oxide film, Cr oxynitride film having a film thickness of 1 to 40 [nm] is formed as a halftone film by sputtering or the like. After that, a second photoresist film 16 is formed on the semi-transmissive film 15 by a coating method.
Here, the light transmittance of the semi-transmissive film 15 is set to 10 to 60%, typically 20% to 55%. The semi-transmissive film 15 does not reverse the phase of the exposure light, and the phase shift angle is, for example, 0.4 to 15 degrees. The optical characteristics of the semi-transmissive film can be adjusted by the film thickness and composition.
　ここでハーフトーン膜である半透過膜の光透過率は、使用目的や顧客の仕様等により決定されるものである。従って、位相シフト膜とエッチングストッパ膜を積層したフォトマスクブランクスを予め準備しておき、顧客等の仕様に合わせてハーフトーン膜を形成することにより、フォトマスクの仕様確定からフォトマスク完成までの製造工期を短縮することができる。 Here, the light transmittance of the semi-transmissive film, which is a halftone film, is determined according to the purpose of use, customer specifications, and the like. Therefore, by preparing a photomask blank in which a phase shift film and an etching stopper film are laminated in advance and forming a halftone film according to the customer's specifications, manufacturing from photomask specification determination to photomask completion The construction period can be shortened.
　次に、図２（Ｃ）に示すように、第２のフォトレジスト膜１６を露光及び現像することにより、第２のフォトレジストパターン１６ａを形成する。 Next, as shown in FIG. 2C, the second photoresist film 16 is exposed and developed to form a second photoresist pattern 16a.
　次に、図２（Ｄ）に示すように、第２のフォトレジストパターン１６ａをマスクに、半透過膜１５をエッチングし、半透過膜のパターン１５ａを形成し、その後アッシング等により第２のフォトレジストパターン１６ａを除去する。
　半透過膜１５のエッチング法として、ウェットエッチング法又はドライエッチング法が使用できるが、高いエッチング選択比が得られるウェットエッチング法が好適に使用できる。
　位相シフト膜１２と同様に半透過膜１５としてＣｒ系の膜を使用する場合、エッチング液として、例えば硝酸第二セリウムアンモニウム水溶液を使用することができる。 Next, as shown in FIG. 2D, the semi-transmissive film 15 is etched using the second photoresist pattern 16a as a mask to form a semi-transmissive film pattern 15a, and then the second photo pattern is formed by ashing or the like. The resist pattern 16a is removed.
A wet etching method or a dry etching method can be used as an etching method for the semi-transmissive film 15, but a wet etching method capable of obtaining a high etching selectivity can be preferably used.
When a Cr film is used as the semi-transmissive film 15 similarly to the phase shift film 12, for example, an aqueous solution of ceric ammonium nitrate can be used as an etching solution.
　次に、図３に示すように、半透過膜のパターン１５ａをマスクに、位相シフト膜のパターン１２ａ、１２ｂ、１２ｃ上のエッチングストッパ膜のパターン１３ａ、１３ｂ、１３ｃをエッチングする。半透過膜のパターン１５ａの下部には、一部のエッチングストッパ膜のパターン１３ｄ、１３ｅが残存する。
　エッチング法として、ウェットエッチング法又はドライエッチング法が使用できるが、高いエッチング選択比が得られるウェットエッチング法が好適に使用できる。エッチング液として、上記のとおりＫＯＨと過酸化水素水の混合液を好適に使用できる。 Next, as shown in FIG. 3, the etching stopper film patterns 13a, 13b, and 13c on the phase shift film patterns 12a, 12b, and 12c are etched using the semi-transmissive film pattern 15a as a mask. A part of the etching stopper film patterns 13d and 13e remain below the semi-transmissive film pattern 15a.
As the etching method, a wet etching method or a dry etching method can be used, but a wet etching method that can obtain a high etching selectivity can be preferably used. As described above, a mixed solution of KOH and hydrogen peroxide water can be suitably used as the etching solution.
　なお、図２（Ｃ）の工程後、第２のフォトレジストパターン１６ａをマスクに、半透過膜１５をエッチングし、半透過膜のパターン１５ａを形成し、位相シフト膜のパターン１２ａ上のエッチングストッパ膜のパターン１３ａをエッチングした後に、第２のフォトレジストパターン１６ａをアッシング等により除去してもよい。 2C, the semi-transmissive film 15 is etched using the second photoresist pattern 16a as a mask to form a semi-transmissive film pattern 15a, and an etching stopper on the phase shift film pattern 12a. After etching the film pattern 13a, the second photoresist pattern 16a may be removed by ashing or the like.
　図３に示される様に、フォトマスク上には、位相シフト膜のパターン１２ａ、１２ｂ、１２ｃ、半透過膜のパターン１５ａが形成され、それ以外の領域では透明な基板１１が露出している。 As shown in FIG. 3, phase shift film patterns 12a, 12b, and 12c, and a semi-transmissive film pattern 15a are formed on the photomask, and the transparent substrate 11 is exposed in the other regions.
　図３において、位相シフト膜のパターン１２ｂ、１２ｃで形成される位相シフト部と半透過膜のパターン１５ａで形成される半透過部との位相差は略１８０［度］となるため、これらの境界部分での位相シフト部と半透過部のパターン１５ａで形成される半透過部との位相差は、半透過膜の位相シフト角をα[度]とすると１８０－αであるが、半透過膜の透過率が高い場合、例えば透過率５４％であればα＝１．１［度］と極めて小さく、位相差は略１８０［度］とみなせる。或いは、必要ならば位相シフト膜１２の膜厚等の微調整により位相差は、１８０±１０［度］の範囲に容易に留めることができる。このためこれらの境界部分でも露光光分布は急峻に変化し、その結果、本フォトマスクを用いて例えばフラットパネル基板上に形成されるフォトレジストのプロファイルは、この境界部分で急峻に変化する。 In FIG. 3, the phase difference between the phase shift portion formed by the phase shift film patterns 12b and 12c and the semi-transmission portion formed by the semi-transmission film pattern 15a is approximately 180 [degrees]. The phase difference between the phase shift portion in the portion and the semi-transmissive portion formed by the pattern 15a of the semi-transmissive portion is 180-α when the phase shift angle of the semi-transmissive film is α [degrees]. For example, when the transmittance is 54%, α = 1.1 [degrees] is extremely small, and the phase difference can be regarded as approximately 180 [degrees]. Alternatively, if necessary, the phase difference can be easily kept within a range of 180 ± 10 [degrees] by fine adjustment of the thickness of the phase shift film 12 or the like. For this reason, the exposure light distribution also changes steeply at these boundary portions, and as a result, the profile of a photoresist formed on, for example, a flat panel substrate using the present photomask changes sharply at the boundary portions.
　また、基板が露出した透明部と位相シフト膜で形成される位相シフト部との位相シフト角も略１８０度であるため、これらの境界においても、露光により形成されたフォトレジストのプロファイルも急峻となる。
　その結果、ハーフトーンの効果と位相シフトの効果を両立できるフォトマスクを実現することができる。 In addition, since the phase shift angle between the transparent portion where the substrate is exposed and the phase shift portion formed of the phase shift film is approximately 180 degrees, the profile of the photoresist formed by exposure is also steep at these boundaries. Become.
As a result, it is possible to realize a photomask that can achieve both a halftone effect and a phase shift effect.
　なお上述のように、位相シフト部と半透過部とが隣接する境界部には、エッチングストッパ膜のパターン１３ｄ、１３ｅが残存する。境界部分において残存するエッチングストッパ膜のパターン１３ｄ、１３ｅの幅は、第２のフォトレジストパターン１６ａを露光するためのフォトマスク描画装置（レーザー描画装置）の位置合わせ誤差（アライメントずれ）に相当する量である。その結果、半透過部と位相シフト部とが重ね合わせズレで、間隙が生ずること無く隣接させることが可能となる。 As described above, the etching stopper film patterns 13d and 13e remain at the boundary portion where the phase shift portion and the semi-transmissive portion are adjacent to each other. The width of the etching stopper film patterns 13d and 13e remaining at the boundary portion is an amount corresponding to an alignment error (alignment deviation) of a photomask drawing apparatus (laser drawing apparatus) for exposing the second photoresist pattern 16a. It is. As a result, the semi-transmissive portion and the phase shift portion are overlapped and can be adjacent to each other without generating a gap.
　また、エッチングストッパ膜のパターン１３ｄ、１３ｅの幅は、フォトマスクパターンによってフォトレジストを露光する場合、露光結果に影響を与えない範囲の寸法に設定する。すなわち、エッチングストッパ膜のパターン１３ｄ、１３ｅの幅は、フォトマスクを用いてフォトレジストを露光する投影（プロジェクション）露光装置の解像限界以下に設定する。
　上記投影露光装置の解像限界の値については、経験則として以下の式
λ／（２ＮＡ）
を用いることができる。ここで、λは投影露光装置の波長（代表波長）であり、ＮＡは投影露光装置の開口数である。エッチングストッパ膜のパターン１３ｄ、１３ｅの幅を、この解像限界以下とすることで、フォトレジストの露光結果に影響を与えることは無い。 The widths of the etching stopper film patterns 13d and 13e are set to dimensions that do not affect the exposure result when the photoresist is exposed by the photomask pattern. That is, the widths of the etching stopper film patterns 13d and 13e are set to be equal to or less than the resolution limit of a projection exposure apparatus that exposes the photoresist using a photomask.
As a rule of thumb, the value of the resolution limit of the projection exposure apparatus is expressed by the following equation λ / (2NA)
Can be used. Here, λ is the wavelength (representative wavelength) of the projection exposure apparatus, and NA is the numerical aperture of the projection exposure apparatus. By setting the width of the etching stopper film patterns 13d and 13e to be equal to or less than the resolution limit, the exposure result of the photoresist is not affected.
　具体的には、境界部分の１３ｄ、１３ｅの幅（設定値）をフォトマスク描画装置の位置合わせ誤差ｄ［μｍ］と設定することによって、作製されるフォトマスクでの１３ｄ、１３ｅの実際の幅（実測値）は０から２ｄの範囲に収まる。レーザー描画装置のｄの典型的な値は、例えば０．５［μｍ］であり、フォトマスクでの境界部の実際の幅は０～１［μｍ］となる。
　また、現在、広く用いられているフラットパネルディスプレイ用途の投影露光装置では、ＮＡは０．０９程度、代表波長λは３６５［ｎｍ］である。これらの値を上式にあてはめると解像限界の値は２．０［μｍ］となる。この解像限界の値と比較し、上記レーザー描画装置の位置合わせ誤差は十分に小さい。従って、上記エッチングストッパ膜のパターン１３ｄ、１３ｅの幅をフォトマスク描画装置の位置合わせ誤差に設定することにより、実使用上、フォトレジストの投影露光装置の解像限界以下となり、上記２つの条件は両立させることが可能である。 Specifically, the actual widths of 13d and 13e in the produced photomask are set by setting the widths (set values) of the boundary portions 13d and 13e as the alignment error d [μm] of the photomask drawing apparatus. The (actual measured value) falls within the range of 0 to 2d. A typical value of d of the laser drawing apparatus is, for example, 0.5 [μm], and the actual width of the boundary portion in the photomask is 0 to 1 [μm].
Further, in the currently widely used projection exposure apparatus for flat panel displays, the NA is about 0.09 and the representative wavelength λ is 365 [nm]. When these values are applied to the above equation, the resolution limit value is 2.0 [μm]. Compared with the value of the resolution limit, the alignment error of the laser drawing apparatus is sufficiently small. Therefore, by setting the widths of the etching stopper film patterns 13d and 13e to the alignment error of the photomask drawing apparatus, the actual conditions will be less than the resolution limit of the photoresist projection exposure apparatus. It is possible to achieve both.
　本実施形態のフォトマスクについて、例えば、位相シフト膜のパターン１２ｂ、１２ｃをＴＦＴのソースドレイン電極、半透過膜のパターン１５ａをＴＦＴのチャネル領域のパターン形成に使用できる。ソースドレイン領域とチャネル領域の境界部分のフォトレジスト膜のプロファイルが急峻となり、またソースドレイン電極のエッジ部分も急峻となるため、ＴＦＴの微細化が実現できる。 For the photomask of this embodiment, for example, the phase shift film patterns 12b and 12c can be used for TFT source / drain electrodes, and the semi-transmissive film pattern 15a can be used for pattern formation of the TFT channel region. Since the profile of the photoresist film at the boundary between the source / drain region and the channel region becomes steep, and the edge portion of the source / drain electrode also becomes steep, miniaturization of the TFT can be realized.
　図４は、ハーフトーン膜と位相シフト膜とを組み合わせた本実施形態により露光したフォトレジストの形状と、ハーフトーン膜と露光光を透過しない遮光膜とを組み合わせた従来のフォトマスクにより露光したフォトレジストの形状とを比較して示す。 FIG. 4 shows a photo exposed by a conventional photomask in which the shape of the photoresist exposed by this embodiment combining a halftone film and a phase shift film and a halftone film and a light-shielding film that does not transmit exposure light are combined. A comparison with the resist shape is shown.
　図４（ａ）は、本実施形態のフォトマスクの断面であり、図４（ａ）は図３の一部を拡大した図である。図４（ｂ）は、特許文献１に開示される従来のフォトマスクの断面の一部であり、透明基板４２上にハーフトーン膜のパターン４３が形成され、ハーフトーン膜のパターン４３上にバリア膜（エッチングストッパ膜）のパターン４４及び遮光膜のパターン４５が形成されている。 FIG. 4A is a cross-sectional view of the photomask of the present embodiment, and FIG. 4A is an enlarged view of a part of FIG. FIG. 4B is a part of a cross section of a conventional photomask disclosed in Patent Document 1, in which a halftone film pattern 43 is formed on a transparent substrate 42, and a barrier is formed on the halftone film pattern 43. A film (etching stopper film) pattern 44 and a light shielding film pattern 45 are formed.
　図４（ｃ）は、図４（ａ）に示すフォトマスクにより露光されたフォトレジスト３０の断面形状を模式的に示す。ハーフトーン膜である半透過膜に相当する箇所のフォトレジスト膜厚は、位相シフト膜に相当する箇所のフォトレジスト膜厚より薄く、１つのフォトマスクにより、１回の露光で異なるフォトレジスト膜厚を有する領域を形成することができる。
　図４（ｃ）において、黒丸で示す点Ｐは、ハーフトーン膜である半透過膜と位相シフト膜との境界に相当する箇所を示す。 FIG. 4C schematically shows a cross-sectional shape of the photoresist 30 exposed by the photomask shown in FIG. The photoresist film thickness at the portion corresponding to the semi-transmissive film, which is a halftone film, is thinner than the photoresist film thickness at the position corresponding to the phase shift film, and different photoresist film thicknesses by one exposure with one photomask. A region having can be formed.
In FIG. 4C, a point P indicated by a black circle indicates a portion corresponding to the boundary between the semi-transmissive film that is a halftone film and the phase shift film.
　同様に、従来のフォトマスクを用いて、異なる膜厚を有するフォトレジスト４０を１回の露光で形成することができ、図４（ｄ）は、図４（ｂ）に示すフォトマスクにより露光されたフォトレジスト４０の断面形状を模式的に示す。図４（ｄ）中の黒丸で示す点Ｑは、ハーフトーン膜と遮光膜との境界に相当する箇所を示す。 Similarly, using a conventional photomask, a photoresist 40 having different film thicknesses can be formed by one exposure, and FIG. 4D is exposed by the photomask shown in FIG. The cross-sectional shape of the photoresist 40 is schematically shown. A point Q indicated by a black circle in FIG. 4D indicates a portion corresponding to the boundary between the halftone film and the light shielding film.
　図４（ｅ）は各フォトレジスト３０、４０の点Ｐ及びＱでの傾斜角を比較して示すグラフである。図４（ｅ）より明らかなように、従来のフォトマスクの点Ｑの傾斜角と比較し、本実施形態によるフォトマスクの点Ｐの傾斜角は大きく、フォトレジスト３０の境界部分の断面形状が急峻になることが理解できる。
　すなわち、従来のフォトマスクによりフォトレジストを露光した場合と比較し、本実施形態によるフォトマスクによりフォトレジストを露光することにより、フォトレジスト膜の形状が改善され、レジスト膜厚が変化する境界領域において、急峻な断面形状を得ることができる。 FIG. 4E is a graph showing the inclination angles of the photoresists 30 and 40 at points P and Q in comparison. As apparent from FIG. 4E, the inclination angle of the point P of the photomask according to the present embodiment is larger than the inclination angle of the point Q of the conventional photomask, and the cross-sectional shape of the boundary portion of the photoresist 30 is larger. It can be understood that it becomes steep.
That is, in comparison with the case where the photoresist is exposed by the conventional photomask, the photoresist film is improved by exposing the photoresist by the photomask according to the present embodiment, and in the boundary region where the resist film thickness changes. A steep cross-sectional shape can be obtained.
（実施形態２）
　上記実施形態１においては、透明基板上に位相シフト膜を形成後に半透過膜を形成したが、透明基板上に半透過膜を形成し、その後位相シフト膜を形成することによりフォトマスクを製造してもよい。
　以下、図を参照し、フォトマスクの製造方法について説明するが、透明基板、位相シフト膜、半透過膜、エッチングストッパ膜としては、実施形態１と同様の膜を使用することができる。 (Embodiment 2)
In Embodiment 1 above, the semi-transmissive film is formed after the phase shift film is formed on the transparent substrate. However, the photomask is manufactured by forming the semi-transmissive film on the transparent substrate and then forming the phase shift film. May be.
Hereinafter, a photomask manufacturing method will be described with reference to the drawings. However, as the transparent substrate, the phase shift film, the semi-transmissive film, and the etching stopper film, films similar to those in Embodiment 1 can be used.
　図５（Ａ）に示すように、合成石英ガラス等の透明基板２１上に、ハーフトーン膜として、半透過膜２２をスパッタ法等により形成し、その上に、エッチングストッパ膜２３をスパッタ法等により成膜することにより、フォトマスクブランクス２０を準備する。 As shown in FIG. 5A, a semi-transmissive film 22 is formed as a halftone film on a transparent substrate 21 such as synthetic quartz glass by a sputtering method or the like, and an etching stopper film 23 is formed thereon by a sputtering method or the like. The photomask blanks 20 are prepared by forming a film by the above.
　次に、エッチングストッパ膜２３上に第３のフォトレジスト膜２４を塗布法により形成する。 Next, a third photoresist film 24 is formed on the etching stopper film 23 by a coating method.
　次に図５（Ｂ）に示すように、第３のフォトレジスト膜２４を露光及び現像することにより、第３のフォトレジストパターン２４ａを形成する。 Next, as shown in FIG. 5B, the third photoresist film 24 is exposed and developed to form a third photoresist pattern 24a.
　次に図５（Ｃ）に示すように、第３のフォトレジストパターン２４ａをマスクにエッチングストッパ膜２３をエッチングし、エッチングストッパ膜のパターン２３ａを形成する。 Next, as shown in FIG. 5C, the etching stopper film 23 is etched using the third photoresist pattern 24a as a mask to form an etching stopper film pattern 23a.
　　次に図６（Ａ）に示すように、第３のフォトレジストパターン２４ａをアッシング等により除去し、その後にエッチングストッパ膜のパターン２３ａをマスクに半透過膜２２をエッチングし、半透過膜のパターン２２ａを形成する。 Next, as shown in FIG. 6A, the third photoresist pattern 24a is removed by ashing or the like, and then the semi-transmissive film 22 is etched using the pattern 23a of the etching stopper film as a mask. 22a is formed.
　　また、図５（Ｃ）の工程後、半透過膜２２をエッチングし、半透過膜のパターン２２ａを形成した後に、アッシング法等により第３のフォトレジストパターン２４ａを除去してもよい。この場合、エッチングストッパ膜２３のエッチング工程と半透過膜２２のエッチング工程を連続して行うこともでき、エッチングストッパ膜２３のエッチング工程において半透過膜２２に対して高いエッチング選択比を必ずしも確保する必要が無い。
　　ただし、図２（Ａ）の工程と同様に、エッチングストッパ膜のパターン２３ａをマスクに半透過膜２２をエッチングすることにより、両膜のサイドエッチングの抑制に効果的である。 Further, after the step of FIG. 5C, the semi-transmissive film 22 may be etched to form the semi-transmissive film pattern 22a, and then the third photoresist pattern 24a may be removed by an ashing method or the like. In this case, the etching step of the etching stopper film 23 and the etching step of the semi-transmissive film 22 can be performed continuously, and a high etching selectivity with respect to the semi-transmissive film 22 is not necessarily ensured in the etching step of the etching stopper film 23. There is no need.
However, as in the step of FIG. 2A, etching the semi-transmissive film 22 using the pattern 23a of the etching stopper film as a mask is effective in suppressing side etching of both films.
　次に、図６（Ｂ）に示すように、位相シフト膜２５、をスパッタ法等により形成し、その後、位相シフト膜２５上に第４のフォトレジスト膜２６を塗布法により形成する。 Next, as shown in FIG. 6B, a phase shift film 25 is formed by a sputtering method or the like, and then a fourth photoresist film 26 is formed on the phase shift film 25 by a coating method.
　次に、図６（Ｃ）に示すように、第４のフォトレジスト膜２６を露光及び現像することにより、第４のフォトレジストパターン２６ａ、２６ｂ、２６ｃを形成する。 Next, as shown in FIG. 6C, the fourth photoresist film 26 is exposed and developed to form fourth photoresist patterns 26a, 26b, and 26c.
　次に、図６（Ｄ）に示すように、第４のフォトレジストパターン２６ａ、２６ｂ、２６ｃをマスクに、位相シフト膜２５をエッチングし、位相シフト膜のパターン２５ａ、２５ｂ、２５ｃを形成し、その後アッシング等により第４のフォトレジストパターン２６ａ、２６ｂ、２６ｃを除去する。 Next, as shown in FIG. 6D, the phase shift film 25 is etched using the fourth photoresist patterns 26a, 26b, and 26c as masks to form phase shift film patterns 25a, 25b, and 25c. Thereafter, the fourth photoresist patterns 26a, 26b, and 26c are removed by ashing or the like.
　次に、図７に示すように、位相シフト膜のパターン２５ａ、２５ｂをマスクに、半透過膜のパターン２２ａ上のエッチングストッパ膜のパターン２３ａをエッチングする。 Next, as shown in FIG. 7, the pattern 23a of the etching stopper film on the pattern 22a of the semi-transmissive film is etched using the patterns 25a and 25b of the phase shift film as a mask.
　なお、図６（Ｃ）の工程後、第４のフォトレジストパターン２６ａをマスクに、位相シフト膜２５をエッチングし、位相シフト膜のパターン２５ａ、２５ｂ、２５ｃを形成し、半透過膜のパターン２２ａ上のエッチングストッパ膜のパターン２３ａをエッチングした後に、第４のフォトレジストパターン２６ａをアッシング等により除去してもよい。 6C, the phase shift film 25 is etched using the fourth photoresist pattern 26a as a mask to form phase shift film patterns 25a, 25b, and 25c, and a semi-transmissive film pattern 22a. After the etching stopper film pattern 23a is etched, the fourth photoresist pattern 26a may be removed by ashing or the like.
　図７において、位相シフト膜のパターン２５ａ、２５ｂにより形成される位相シフト部と半透過膜のパターン２２ａの半透過部との位相差は半透過膜の位相シフト角をα[度]とすると１８０－αであるが、半透過膜の透過率が高い場合、例えば透過率５４％であればα＝１．１度と極めて小さく、位相差は略１８０［度］とみなせる。或いは、必要ならば位相シフト膜１２の膜厚等の微調整により位相差は、１８０±１０［度］の範囲に容易に留めることができる。このためこの境界部分でも露光光分布は急峻に変化し、その結果、本フォトマスクを用いて例えばフラットパネル基板上に形成されるフォトレジストのプロファイルは、対応する境界部分で急峻に変化する。
　また、位相シフト部と基板が露出した透光部との位相差も略１８０度であるため、その境界部分での露光光分布は急峻に変化し、本フォトマスクを用いて形成されるフォトレジストのプロファイルは、対応する境界部分で急峻な形状とすることができる。 In FIG. 7, the phase difference between the phase shift part formed by the phase shift film patterns 25a and 25b and the semi-transmission part of the semi-transmission film pattern 22a is 180 when the phase shift angle of the semi-transmission film is α [degrees]. Although it is −α, when the transmissivity of the semi-transmissive film is high, for example, if the transmittance is 54%, α = 1.1 degrees is extremely small, and the phase difference can be regarded as approximately 180 [degrees]. Alternatively, if necessary, the phase difference can be easily kept within a range of 180 ± 10 [degrees] by fine adjustment of the thickness of the phase shift film 12 or the like. For this reason, the exposure light distribution changes steeply even in this boundary portion, and as a result, the profile of a photoresist formed on, for example, a flat panel substrate using this photomask changes sharply in the corresponding boundary portion.
In addition, since the phase difference between the phase shift portion and the transparent portion where the substrate is exposed is also approximately 180 degrees, the exposure light distribution at the boundary portion changes abruptly, and a photoresist formed using this photomask. The profile can be a steep shape at the corresponding boundary portion.
　本発明は、フォトリソグラフィー工程の削減と、パターンの微細化を実現することができるフォトマスクを提供することができ、産業上の利用可能性は極めて大きい。 The present invention can provide a photomask capable of realizing a reduction in photolithography process and miniaturization of a pattern, and its industrial applicability is extremely large.
１０　フォトマスクブランクス
１１　透明基板
１２　位相シフト膜
１２ａ、１２ｂ、１２ｃ　位相シフト膜のパターン
１３　エッチングストッパ膜
１３ａ、１３ｂ、１３ｃ、１３ｄ、１３ｅ　エッチングストッパ膜のパターン
１４　第１のフォトレジスト膜
１４ａ、１４ｂ、１４ｃ　第１のフォトレジストパターン
１５　半透過膜
１５ａ　半透過膜のパターン
１６　第２のフォトレジスト膜
１６ａ　第２のフォトレジストパターン
２０　フォトマスクブランクス
２１　透明基板
２２　半透過膜
２２ａ　半透過膜のパターン
２３　エッチングストッパ膜
２３ａ　エッチングストッパ膜のパターン
２４　第３のフォトレジスト膜
２５　位相シフト膜
２５ａ、２５ｂ、２５ｃ　位相シフト膜のパターン
２６　第４のフォトレジスト膜
２６ａ、２６ｂ、２６ｃ　第４のフォトレジストパターン
３０　フォトレジスト
４０　フォトレジスト
４２　透明基板
４３　ハーフトーン膜のパターン
４４　バリア膜のパターン
４５　遮光膜のパターン DESCRIPTION OF SYMBOLS 10 Photomask blank 11 Transparent substrate 12 Phase shift film 12a, 12b, 12c Phase shift film pattern 13 Etching stopper film 13a, 13b, 13c, 13d, 13e Etching stopper film pattern 14 First photoresist film 14a, 14b, 14c First photoresist pattern 15 Semi-transmissive film 15a Semi-transmissive film pattern 16 Second photoresist film 16a Second photoresist pattern 20 Photomask blanks 21 Transparent substrate 22 Semi-transmissive film 22a Semi-transmissive film pattern 23 Etching Stopper film 23a Etching stopper film pattern 24 Third photoresist film 25 Phase shift film 25a, 25b, 25c Phase shift film pattern 26 Fourth photoresist film 26a, 26b, 26c Fourth photoresist Pattern of turns 30 photoresist 40 photoresist 42 transparent substrate 43 pattern 45 light-shielding film pattern 44 barrier film of the halftone film

Claims (9)

  1. 　透明基板上に半透過部、位相シフト部、境界部及び透光部を有し、
    　前記透光部は、前記透明基板が露出した部分からなり、
    　前記半透過部は、前記透明基板上に設けられた半透過膜で形成され、
    　前記位相シフト部は前記透明基板上に設けられた位相シフト膜で形成され、
    　前記境界部は、前記半透過部と前記位相シフト部とが隣接する領域に形成され、
    　前記境界部の幅が一定幅以下であり、
    　前記境界部は、前記位相シフト膜、エッチングストッパ膜、前記半透過膜がこの順に形成された積層構造膜で形成される一方、前記境界部を除く前記半透過部、前記位相シフト部及び前記透光部の前記エッチングストッパ膜は除去され、
    　前記境界部の幅は、前記フォトマスクが用いられる投影露光装置の解像限界以下である
    　ことを特徴とするフォトマスク。     Having a transflective part, a phase shift part, a boundary part and a translucent part on a transparent substrate;
    The translucent part consists of a portion where the transparent substrate is exposed,
    The semi-transmissive portion is formed of a semi-transmissive film provided on the transparent substrate,
    The phase shift part is formed of a phase shift film provided on the transparent substrate,
    The boundary portion is formed in a region where the semi-transmissive portion and the phase shift portion are adjacent to each other,
    The width of the boundary is not more than a certain width;
    The boundary portion is formed of a laminated structure film in which the phase shift film, the etching stopper film, and the semi-transmissive film are formed in this order, while the semi-transmissive portion, the phase shift portion, and the transparent portion excluding the boundary portion. The etching stopper film of the optical part is removed,
    A width of the boundary portion is equal to or less than a resolution limit of a projection exposure apparatus in which the photomask is used.
  2. 　透明基板に半透過部、位相シフト部、境界部及び透光部を有し、
    　前記透光部は前記透明基板が露出した部分からなり、
    　前記半透過部は前記透明基板上に設けられた半透過膜で形成され、
    　前記位相シフト部は前記透明基板上に設けられた位相シフト膜で形成され、
    　前記境界部は、前記半透過部と前記位相シフト部とが隣接する領域に形成され、
    　前記境界部の幅が一定幅以下であり、
    　前記境界部は、前記半透過膜、エッチングストッパ膜、前記位相シフト膜がこの順に形成される一方、前記境界部を除く前記半透過部、前記位相シフト部及び前記透光部の前記エッチングストッパ膜は除去され、
    　前記境界部の幅は、前記フォトマスクが用いられる投影露光装置の解像限界以下である
    　ことを特徴とするフォトマスク。     A transparent substrate has a semi-transmissive part, a phase shift part, a boundary part, and a translucent part,
    The translucent part consists of a portion where the transparent substrate is exposed,
    The semi-transmissive part is formed of a semi-permeable film provided on the transparent substrate,
    The phase shift part is formed of a phase shift film provided on the transparent substrate,
    The boundary portion is formed in a region where the semi-transmissive portion and the phase shift portion are adjacent to each other,
    The width of the boundary is not more than a certain width;
    In the boundary portion, the semi-transmissive film, the etching stopper film, and the phase shift film are formed in this order, while the semi-transmissive portion, the phase shift portion, and the light transmitting portion except for the boundary portion are etched stopper films. Is removed,
    A width of the boundary portion is equal to or less than a resolution limit of a projection exposure apparatus in which the photomask is used.
  3. 　前記位相シフト膜は、露光光に対する透過率が１～１０［％］であり、かつ露光光の
    位相が反転することを特徴とする請求項１又は２記載のフォトマスク。     3. The photomask according to claim 1, wherein the phase shift film has a transmittance with respect to exposure light of 1 to 10%, and the phase of the exposure light is reversed.
  4. 　前記半透過膜の露光光に対する透過率は１０～６０［％］であることを特徴とする請
    求項１乃至３のいずれか１項記載のフォトマスク。     The photomask according to any one of claims 1 to 3, wherein a transmittance of the semi-transmissive film with respect to exposure light is 10 to 60 [%].
  5. 　前記位相シフト膜と前記半透過膜とは、同じエッチング液によりエッチング可能であ
    り、
    　前記エッチングストッパ膜は、前記エッチング液に対してエッチング選択性を有する　ことを特徴とする請求項１乃至４のいずれか１項記載のフォトマスク。     The phase shift film and the semi-transmissive film can be etched with the same etchant,
    The photomask according to claim 1, wherein the etching stopper film has etching selectivity with respect to the etching solution.
  6. 　前記エッチングストッパ膜はＴｉ系膜で構成され、前記位相シフト膜はＣｒ酸化膜で構成される
    　ことを特徴とする請求項５記載のフォトマスク。     The photomask according to claim 5, wherein the etching stopper film is made of a Ti-based film, and the phase shift film is made of a Cr oxide film.
  7. 　請求項１記載のフォトマスクを製造するためのフォトマスクブランクスであって、
    前記透明基板上に前記位相シフト膜及び前記エッチングストッパ膜が、この順に積層されたことを特徴とするフォトマスクブランクス。     A photomask blank for producing the photomask according to claim 1,
    A photomask blank, wherein the phase shift film and the etching stopper film are laminated in this order on the transparent substrate.
  8. 　透明基板上に位相シフト膜及びエッチングストッパ膜をこの順に積層する工程と、
    　第１のフォトレジスト膜を形成する工程と、
    　前記第１のフォトレジスト膜をパターニングする工程と、
    　前記第１のフォトレジスト膜をマスクに前記エッチングストッパ膜をエッチングする工程と、
    　前記エッチングストッパ膜をマスクに前記位相シフト膜をエッチングする工程と、
    　前記第１のフォトレジスト膜を除去する工程と、
    　半透過膜を形成する工程と、
    　第２のフォトレジスト膜を形成する工程と、
    　エッチングされた前記エッチングストッパ膜と前記投影露光装置の解像限界以下の幅の重なりを有するよう前記第２のフォトレジスト膜をパターニングする工程と、
    　前記第２のフォトレジスト膜をマスクに前記半透過膜をエッチングする工程と、
    　前記第２のフォトレジスト膜を除去する工程と、
    　前記半透過膜をマスクに前記位相シフト膜上の前記エッチングストッパ膜をエッチングし、前記境界部を除く前記エッチングストッパ膜を除去する工程と
    　を含むことを特徴とする請求項１記載のフォトマスクの製造方法。     A step of laminating a phase shift film and an etching stopper film in this order on a transparent substrate;
    Forming a first photoresist film;
    Patterning the first photoresist film;
    Etching the etching stopper film using the first photoresist film as a mask;
    Etching the phase shift film using the etching stopper film as a mask;
    Removing the first photoresist film;
    Forming a semipermeable membrane;
    Forming a second photoresist film;
    Patterning the second photoresist film so as to have an overlap of the etched stopper film and the width below the resolution limit of the projection exposure apparatus;
    Etching the semi-transmissive film using the second photoresist film as a mask;
    Removing the second photoresist film;
    2. The method of claim 1, further comprising: etching the etching stopper film on the phase shift film using the semi-transmissive film as a mask, and removing the etching stopper film excluding the boundary portion. Production method.
  9. 　透明基板上に半透過膜及びエッチングストッパ膜をこの順に積層する工程と、
    　第３のフォトレジスト膜を形成する工程と、
    　前記第３のフォトレジスト膜をパターニングする工程と、
    　前記第３のフォトレジスト膜をマスクに前記エッチングストッパ膜をエッチングする
    工程と、
    　前記エッチングストッパ膜をマスクに前記半透過膜をエッチングする工程と、
    　前記第３のフォトレジスト膜を除去する工程と、
    　位相シフト膜を形成する工程と、
    　第４のフォトレジスト膜を形成する工程と、
    　エッチングされた前記エッチングストッパ膜と前記投影露光装置の解像限界以下の幅の重なりを有するよう前記第４のフォトレジスト膜をパターニングする工程と、
    　前記第４のフォトレジスト膜をマスクに前記位相シフト膜をエッチングする工程と、
    　前記第４のフォトレジスト膜を除去する工程と、
    　前記位相シフト膜をマスクに前記半透過膜上の前記エッチングストッパ膜をエッチングし、前記境界部を除く前記エッチングストッパ膜を除去する工程と
    　を含むことを特徴とする請求項２記載のフォトマスクの製造方法。     A step of laminating a semi-transmissive film and an etching stopper film in this order on a transparent substrate;
    Forming a third photoresist film;
    Patterning the third photoresist film;
    Etching the etching stopper film using the third photoresist film as a mask;
    Etching the semi-transmissive film using the etching stopper film as a mask;
    Removing the third photoresist film;
    Forming a phase shift film;
    Forming a fourth photoresist film;
    Patterning the fourth photoresist film so as to have an overlap of the etched stopper film and the width below the resolution limit of the projection exposure apparatus;
    Etching the phase shift film using the fourth photoresist film as a mask;
    Removing the fourth photoresist film;
    3. The photomask according to claim 2, further comprising: etching the etching stopper film on the semi-transmissive film using the phase shift film as a mask, and removing the etching stopper film excluding the boundary portion. Production method.
PCT/JP2017/046369 2016-12-28 2017-12-25 Halftone mask, photomask blank, and method for manufacturing halftone mask WO2018123939A1 (en)

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