Method for manufacturing photomask

Abstract

To form a rim portion in a self-aligned manner in a method for manufacturing a photomask.SOLUTION: A method for manufacturing a photomask having a transfer pattern comprises: preparing a photomask blank in which a lower film and an upper film are formed on a transparent substrate; forming a first resist pattern on the upper film; forming an upper pattern by selectively etching the upper film relative to the lower film using the first resist pattern as a mask; forming a second resist pattern covering sidewalls of the upper pattern by modifying the first resist pattern; forming a lower pattern by etching the lower film using the second resist pattern as a mask; and removing the second resist pattern. The transfer pattern is composed of a stack of the upper and lower patterns. The photomask has a rim portion that is adjacent to the transfer pattern and composed only of the lower pattern.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a photomask. [Background technology]

[0002] For flat panel displays such as liquid crystal panels, there is a demand for finer patterns in order to improve image quality. When a photomask pattern is transferred to a photoresist film, which is the target of transfer, the edge shape of the photoresist film becomes gentle due to the effects of light diffraction and interference, which may hinder the finer pattern. In order to make the edge shape of the photoresist film steep and enable the formation of a fine pattern, a rim portion for adjusting the intensity distribution of the exposure light may be provided at the edge of the transferred pattern of the photomask. Patent Document 1 discloses a method of forming a light-shielding film pattern, then forming a phase shift film, and patterning the phase shift film to form a rim portion of the phase shift film around the light-shielding film pattern. Patent Document 2 discloses a method in which after forming a film having a laminated structure, a photoresist pattern is formed, an upper layer film and a lower layer film are etched, and then the upper layer film is side-etched. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-13283 A [Patent Document 2] JP 2013-134435 A Summary of the Invention [Problem to be solved by the invention]

[0004] The method disclosed in Patent Document 1 requires two lithography steps, which is complicated, and misalignment may occur between the lower light-shielding pattern and the upper phase-shifting pattern due to misalignment during the exposure process. The method disclosed in Patent Document 2 can solve the problem of misalignment because the upper and lower films are patterned using a resist pattern formed by a single lithography process, but it requires that the upper film be patterned by two etching processes.

[0005] In view of the above problems, an object of the present invention is to provide a method for manufacturing a photomask that enables a rim portion to be formed in a self-aligned manner. [Means for solving the problem]

[0006] The method for producing a photomask according to the present invention includes the steps of: A method for manufacturing a photomask having a transfer pattern, comprising: a photomask blanks preparation step of preparing a photomask blank in which an underlayer film is formed on a transparent substrate and an upper layer film is formed on the underlayer film; a first etching mask forming step of forming a first resist pattern on the upper layer film; a first patterning step of selectively etching the upper layer film with respect to the lower layer film using the first resist pattern as a mask to form an upper layer pattern; a second etching mask forming step of transforming the first resist pattern to form a second resist pattern covering a sidewall of the upper layer pattern; a second patterning step of etching the underlayer film using the second resist pattern as a mask to form an underlayer pattern; an etching mask removing step of removing the second resist pattern; Including, the transfer pattern is formed by laminating the upper layer pattern and the lower layer pattern, The method further comprises the step of forming a rim portion adjacent to the transfer pattern and made up of only the lower layer pattern.

[0007] This method of manufacturing the photomask enables the rim to be formed in a self-aligned manner, and also enables the upper layer to be patterned in a single etching process.

[0008] Further, a method for producing a photomask according to the present invention includes the steps of: A method for manufacturing a photomask having a transfer pattern, comprising: a photomask blanks preparation step of preparing a photomask blank having a lower layer film formed on a transparent substrate, an intermediate film formed on the lower layer film, and an upper layer film formed on the intermediate film; a first etching mask forming step of forming a first resist pattern on the upper layer film; a first patterning step of selectively etching the upper layer film with respect to the intermediate film using the first resist pattern as a mask to form an upper layer pattern; a second etching mask forming step of transforming the first resist pattern to form a second resist pattern covering a sidewall of the upper layer pattern; a second patterning step of etching the intermediate film and the underlayer film using the second resist pattern as a mask to form an intermediate layer pattern and an underlayer pattern; an etching mask removing step of removing the second resist pattern; Including, the transfer pattern is formed by laminating the upper layer pattern, the intermediate layer pattern, and the lower layer pattern, The substrate is characterized by having a rim portion adjacent to the transfer pattern and configured by laminating the intermediate layer pattern and the lower layer pattern.

[0009] This method of manufacturing a photomask enables the rim portion to be formed in a self-aligned manner, enables the upper layer film to be patterned in a single etching process, and also enables the optical properties of the rim portion to be adjusted.

[0010] In the above configuration, In the second etching mask forming step, the first resist pattern may be deformed by carrying out a heat treatment.

[0011] According to such a method for manufacturing a photomask, the first resist pattern flows by heat treatment and can cover the sidewalls of the upper layer pattern.

[0012] In the above configuration, The rim portion may have a transmittance of 3% or more and 70% or less for a representative wavelength of exposure light.

[0013] In the above configuration, The rim portion may have a phase shift angle of 160° or more and 200° or less with respect to a representative wavelength of the exposure light.

[0014] By using such a method for manufacturing a photomask, it is possible to make the edge shape of the resist pattern to be exposed sharp.

[0015] In the above configuration, the intermediate film has etching characteristics different from those of the lower film and the upper film, The underlayer and overlayer may have the same etching characteristics.

[0016] Such a photomask manufacturing method can contribute to reducing the burden of production management.

[0017] In the above configuration, After the etching mask removing step, a third patterning step of selectively etching the intermediate layer pattern with respect to the lower layer pattern using the upper layer pattern as a mask to remove the intermediate layer pattern in the rim portion; The rim portion may be formed only from the lower layer pattern.

[0018] Such a method for manufacturing a photomask makes it possible to adjust the optical characteristics of the rim portion.

[0019] In the above configuration, an intermediate layer mask forming step of forming a third resist pattern that partially covers the intermediate layer pattern after the etching mask removing step; an intermediate layer patterning step of patterning the intermediate layer pattern using the third resist pattern as a mask; an intermediate layer mask removing step of removing the third resist pattern; Including, The rim portion may have a first rim portion formed only from the lower layer pattern, and a second rim portion formed by laminating the intermediate layer pattern and the lower layer pattern.

[0020] This method of manufacturing a photomask makes it possible to form rim portions having different optical characteristics, and can be applied to a variety of transfer patterns. Effect of the Invention

[0021] According to the present invention, in the method of manufacturing a photomask, the rim portion can be formed in a self-aligned manner. [Brief description of the drawings]

[0022] [Figure 1] 1A to 1C are cross-sectional views illustrating the main manufacturing steps of a photomask 100 according to the first embodiment. [Diagram 2] 2A to 2C are cross-sectional views illustrating the main manufacturing steps of the photomask 100 according to the first embodiment. [Diagram 3] 3A and 3B are a plan view and a cross-sectional view that typically show an example in which an upper layer pattern 3a has an opening OP. [Figure 4] FIG. 4 is a cross-sectional view and a plan view showing a process of forming an upper layer pattern 3a having a wiring pattern shape. [Diagram 5]FIG. 5 is a cross-sectional view showing a schematic diagram of a main manufacturing process of the photomask 100 according to the second embodiment. [Figure 6] 6A to 6C are cross-sectional views illustrating the main manufacturing steps of the photomask 100 according to the second embodiment. [Figure 7] FIG. 7 is a schematic plan view of a photomask 100 according to the second embodiment. [Figure 8] FIG. 8 is a cross-sectional view and a plan view showing a process of forming an upper layer pattern 3a having a wiring pattern shape. [Figure 9] 9(A) and 9(B) are a cross-sectional view and a plan view that show a schematic example of a wiring pattern having a rim portion RM formed from an underlying film 2 around its periphery. [Figure 10] FIG. 10 is a cross-sectional view showing a process of forming a pattern provided with rim portions RM having different optical characteristics. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, the embodiments of the present invention will be described with reference to the drawings. However, the following embodiments are not intended to limit the scope of the present invention. In addition, the same reference numerals are used for the same or similar components, and the description thereof may be omitted.

[0024] Furthermore, terms used in this specification that specify shapes, geometric conditions, and the extent thereof, such as "parallel," "orthogonal," and "same," as well as values ​​of length and angle, are not to be bound by strict meanings, but are to be interpreted to include a range within which similar functions can be expected.

[0025] (Embodiment 1) Hereinafter, a method for manufacturing a photomask 100 having a pattern to be transferred to an object to be exposed (referred to as a transfer pattern) will be described with reference to the drawings. 1 and 2 are cross-sectional views that diagrammatically show main manufacturing steps of a photomask 100 according to the first embodiment.

[0026] <Laminated film formation process: Photomask blanks preparation process> 1(A), a lower layer film 2 (for example, but not limited to, a thickness of 5 to 20 nm) is formed on a transparent substrate 1 such as quartz by a film formation method such as PVD or CVD. Then, an upper layer film 3 (for example, but not limited to, a thickness of 30 to 100 nm) is formed on the lower layer film 2. A photomask blank 10 having an underlayer film 2 and an overlayer film 3 on a transparent substrate 1 can be prepared.

[0027] The lower layer film 2 is, for example, a semi-transparent film having semi-transparency, and is formed by a PVD method, a CVD method, or the like using a material such as a metal, a metal compound (e.g., a Cr-based compound, a Ni-based compound, a Ti-based compound, etc.), a metal silicide compound (e.g., Mo silicide, Zr silicide, etc.), a nitride (ZrN, etc.), or the like. In addition, having semi-transparency can mean that the transmittance for a representative wavelength contained in the exposure light (e.g., i-line, h-line, g-line, or any mixed light selected from these) used in the lithography process using the photomask 100 is lower than the transmittance of the transparent substrate 1 and higher than the transmittance of a film having light-shielding properties described below.

[0028] The optical characteristics of the lower layer film 2 can be appropriately set according to the intended use by determining the optical characteristics of the rim portion RM, which will be described later. When the underlayer film 2 is used as a halftone film, for example, the transmittance for the representative wavelength of the exposure light can be set to 3 to 70% (3%≦transmittance≦70%) and the phase shift angle can be set low (for example, higher than 0° and less than 20°). Furthermore, when the underlayer film 2 is used as a phase shift film, for example, the transmittance for the representative wavelength of the exposure light can be set to 3 to 50% (3%≦transmittance≦50%) and the phase shift angle (to invert the phase) can be set to approximately 180° (160°≦phase shift amount≦200°), more preferably 170°≦phase shift amount≦190°.

[0029] The upper film 3 has etching characteristics different from those of the lower film 2 and can be selectively etched with respect to the lower film 2. For example, a film made of a metal, a metal compound, a Si-based compound, a metal silicide compound, etc. is formed by a PVD method, a CVD method, etc. The upper layer film 3 has, for example, a light-shielding property, and preferably has a function of reducing surface reflection. However, rather than the upper layer film 3 alone having light-shielding properties, the upper layer film 2 and the lower layer film 3 may be composed of semi-transparent films, and the laminated structure of the upper layer film 3 and the lower layer film 2 may have light-shielding properties. Incidentally, having light-shielding properties means, for example and without limitation, that the optical density (OD value) is 2.7 or more.

[0030] The laminated structure of the upper layer film 2 and the lower layer film 3 may be semi-transparent. The optical properties of the laminated structure of the upper layer film 2 and the lower layer film 3 can be appropriately set according to the pattern dimensions and shape formed using the photomask 100 and the exposure light used.

[0031] <First etching mask forming process> Next, as shown in the cross-sectional view of FIG. 1(B), a photoresist film 4 (first photoresist film) is formed on the upper layer film 3 by a coating method or the like. Thereafter, as shown in the cross-sectional view of FIG. 1(C), the photoresist film 4 is patterned by exposure using laser drawing or the like and development to form a first resist pattern 4a (first etching mask).

[0032] <First patterning process: Upper layer pattern formation process> Next, as shown in the cross-sectional view of Fig. 2(A), the first resist pattern 4a is used as an etching mask to selectively etch the upper layer film 3 with respect to the lower layer film 2, exposing the surface of the lower layer film 2, and then the sidewall surface of the upper layer film 3 is side-etched and recessed to form an upper layer pattern 3a. As shown in Fig. 2(A), the sidewall surface 3s (upper layer sidewall surface) of the upper layer pattern 3a is recessed by a predetermined amount D from the sidewall surface 4s (resist sidewall surface) of the first resist pattern 4a. The etching is isotropic etching, which may be dry etching, but is preferably wet etching. A known etchant can be used.

[0033] <Second Etching Mask Forming Process> Next, as shown in the cross-sectional view of FIG. 2(B), the first resist pattern 4a is deformed, for example, by heat treatment (for example, at a heat treatment temperature of 200 to 300° C.), to form a second resist pattern 4b (second etching mask). For example, the first resist pattern 4a can be transformed (reflowed) by being fluidized by heat treatment (reflow treatment) at a temperature equal to or higher than the glass transition temperature, into the second resist pattern 4b having a shape covering the sidewall surface 3s of the upper layer pattern 3a. The distance L (coverage amount) covering the sidewall surface 3s is determined depending on the side etching amount D and the heat treatment conditions of the first resist pattern 4a.

[0034] By subjecting the first resist pattern 4a to the heat treatment as described above, it is possible to obtain the second resist pattern 4b in contact with the sidewall surface 3s of the upper layer pattern 3a and the surface 2f of the lower layer film 2. Data on the heat treatment temperature and treatment time for the shape of the first resist pattern 4a is obtained in advance, and the heat treatment conditions (reflow conditions) can be determined based on the obtained data.

[0035] In order to promote the deformation caused by the heat treatment, an exposure process may be added to the first resist pattern 4a. By adjusting (reducing) the deformation temperature of the first resist pattern 4a by exposure, the deformation caused by the flow of the first resist pattern 4a can be promoted. In this case, in the exposure step for forming the first resist pattern 4a, the entire surface may be exposed with a low dose, or an exposure process may be added to the first resist pattern 4a after the step of FIG. 2A.

[0036] Instead of the heat treatment shown in Fig. 2B, the first resist pattern 4a may be reflowed by being fluidized with a chemical solution. The first resist pattern 4a can be deformed by immersing it in a chemical solution that dissolves the first resist pattern 4a or by penetrating the chemical solution by exposure to steam. At this time, a heat treatment may be performed.

[0037] 2A, instead of the process shown in FIG. 2B, a crosslinking resin that crosslinks with an acid may be applied, and then a heat treatment or exposure may be performed to generate acid from the first resist pattern 4a, causing a crosslinking reaction around the first resist pattern 4a to form a coating film made of the crosslinking resin. A coating film that contacts the sidewall surface 3s of the upper layer pattern 3a and the surface 2f of the lower layer film 2 around the first resist pattern 4a may be formed to obtain a second resist pattern 4b.

[0038] <Second patterning process: Lower layer pattern formation process> 2(C), the lower layer film 2 is etched using the second resist pattern 4b as an etching mask to form a lower layer pattern 2a. The upper layer pattern 3a is not etched because it is protected by the second resist pattern 4b. The etching may be a known wet etching, but may be a dry etching.

[0039] In this manner, the first resist pattern 4a formed by a single exposure step such as laser drawing can be used to form the upper layer pattern 3a and the lower layer pattern 2a in different shapes.

[0040] <Etching mask removal process> Next, as shown in the cross-sectional view of FIG. 2(D), the second resist pattern 4b is removed by ashing, wet cleaning, or the like.

[0041] A sidewall surface 3s of the upper layer pattern 3a is recessed from a sidewall surface 2s (lower layer sidewall surface) of the lower layer pattern 2a. The sidewall surface 2s and the sidewall surface 3s are separated from each other, and a surface 2f (lower layer surface) of the lower layer pattern 2a is exposed, forming a rim portion RM composed only of the lower layer pattern 2a. The rim portion RM is formed in a self-aligned manner adjacent to a laminate pattern (first laminate pattern) consisting of a laminate structure of a lower layer pattern 2a and an upper layer pattern 3a, and the rim portion RM becomes a single layer (single layer pattern) consisting of the lower layer pattern 2a. The rim portion RM has a width W, and the width W of the rim portion can be determined by the amount of coverage L. If there is no side etching of the lower layer 2, the width W of the rim portion will be equal to the amount of coverage L. The width W of the rim portion can be set to, for example, 0.1 μm to 2 μm, typically 0.2 to 0.8 μm. A laminated pattern consisting of a laminated structure of a lower layer pattern 2a and an upper layer pattern 3a constitutes the transfer pattern, and a rim portion RM is formed adjacent to the edge portion of the transfer pattern and constitutes an auxiliary pattern that can adjust the intensity distribution of the exposure light, etc.

[0042] The optical characteristics of the rim portion RM are determined by the lower layer film 2. The optical characteristics required for the region other than the rim portion RM can be realized by the optical characteristics of the laminated structure of the lower layer film 2 and the upper layer film 3. For example, if the rim portion RM has semi-transparency and is further made a phase shift region, and a laminated pattern consisting of a laminated structure of a lower layer film 2 and an upper layer film 3 is made a light-shielding pattern, the laminated structure of the lower layer film 2 and the upper layer film 3 can be set to have light-shielding properties. Furthermore, when semi-transmittance is required as the optical property of the region other than the rim portion RM, the laminated structure of the lower layer film 2 and the upper layer film 3 should realize the desired transmittance.

[0043] By making the rim portion RM made of the underlayer film 2 function as a phase inversion portion or a halftone portion that adjusts the intensity of transmitted light, the light intensity distribution at the edge portion of the resist to be exposed can be improved. As a result, the rim portion RM can improve the resolution of the transfer pattern. The same applies to the other embodiments below.

[0044] The first resist pattern 4a is formed in a single lithography process, and the rim portion RM is formed in a self-aligned manner without any misalignment with the lower layer pattern 2a (or upper layer pattern 3a). Moreover, the upper layer film 3 can be patterned to form the upper layer pattern 3a in a single etching step, which can contribute to reducing the number of etching steps.

[0045] In addition, in the lower layer film patterning step, the upper layer film 3 is not etched because it is covered with the second resist pattern 4b, so there is no need to selectively etch the lower layer film 2 with respect to the upper layer film 3, and this has the effect of increasing the number of options for etchants.

[0046] The transfer pattern provided on the photomask 100 may have any pattern shape. Therefore, the shape of the upper layer pattern 3a is not limited, and the upper layer pattern 3a can have various shapes. The upper layer pattern 3a may have a shape for opening the hole HL, for example. 3A and 3B are a plan view and a cross-sectional view that typically show an example in which an upper layer pattern 3a has an opening OP. Within an opening OP of the upper layer pattern 3a, a rim portion RM having a predetermined width W is evenly formed along the inner periphery of the opening OP. A hole HL is provided within the rim portion RM, and the surface of the transparent substrate 1 is exposed through the hole HL.

[0047] The upper layer pattern 3a may have a wiring pattern shape, for example, in order to form a wiring pattern on an object to be exposed. FIG. 4 is a cross-sectional view and a plan view showing a process of forming an upper layer pattern 3a having a wiring pattern shape.

[0048] 4(A), similarly to the steps shown in Figures 1(A), (B), (C) and 2(A), a lower layer film 2 and an upper layer film 3 are formed on a transparent substrate 1, and a first resist pattern 4a is formed on the upper layer film 3. Thereafter, the upper layer film 3 is selectively etched using the first resist pattern 4a as an etching mask, to form an upper layer pattern 3a. The amount of side etching of the upper layer 3 can be appropriately set depending on the pattern to be formed.

[0049] As shown in FIG. 4(B), similarly to the step shown in FIG. 2(B), the first resist pattern 4a is deformed to form a second resist pattern 4b covering the upper layer pattern 3a.

[0050] As shown in Figures 4(C) and (D), similar to the process shown in Figures 2(C) and (D), the underlayer film 2 is etched using the second resist pattern 4b as an etching mask to form a underlayer pattern 2a, and then the second resist pattern 4b is removed.

[0051] 4(D) is a plan view showing the shapes of the upper layer pattern 3a and the rim portion RM, and shows one end of the wiring pattern LN defined by the upper layer pattern 3a. The other end of the wiring pattern LN is similar. The wiring pattern LN is a laminated pattern of an upper layer pattern 3a and a lower layer pattern 2a, and a rim portion RM of width W is formed uniformly in a self-aligned manner so as to surround the outer periphery of the wiring pattern LN. The wiring pattern may be straight or curved, is not limited to wiring, and may be rectangular like a capacitor electrode, and the shape is not limited.

[0052] (Embodiment 2) An intermediate film 5 may be provided between the lower film 2 and the upper film 3 . The intermediate film 5 has different etching characteristics with respect to the upper film 3 and the lower film 2, and can function as an etching stopper film. The intermediate film 5 can also function as an adjustment film for adjusting optical characteristics. 5 and 6 are cross-sectional views that diagrammatically show main manufacturing steps of the photomask 100 according to the second embodiment, and FIG. 7 is a plan view that diagrammatically shows the photomask 100 according to the second embodiment.

[0053] <Laminated film formation process: Photomask blanks preparation process> 5(A), after a lower layer film 2 is formed on a transparent substrate 1 such as quartz, an intermediate film 5 is formed on the lower layer film 2 to a thickness of, for example, but not limited to, 1 nm to 50 nm by a film formation method such as PVD or CVD, and then an upper layer film 3 is formed. A photomask blank having a laminated structure of the lower layer film 2, the intermediate film 5, and the upper layer film 3 on the transparent substrate 1 is obtained.

[0054] The optical properties of the intermediate film 5 are not particularly limited, but preferably, for example, the transmittance to the exposure light is 10% or more and 75% or less, and the phase shift angle can be set low, such as greater than 0° and less than 20°. Further, instead of the laminated structure of the lower layer film 2 and the upper layer film 3 having the light-shielding properties, the laminated structure of the lower layer film 2, the intermediate film 5 and the upper layer film 3 may have the light-shielding properties. Furthermore, the laminated structure of the lower layer film 2, the intermediate film 5, and the upper layer film 3 may be semi-permeable.

[0055] Although the lower layer 2 and the upper layer 3 have the above-mentioned configurations, the lower layer 2 and the upper layer 3 may have different etching characteristics or may have the same etching characteristics. When the lower film 2 and the upper film 3 have the same etching characteristics, the lower film 2 and the upper film 3 can be etched with the same etchant. For example, as a combination of the lower film 2, the upper film 3, and the intermediate film 5, when the lower film 2 and the upper film 3 have different etching characteristics, a non-limiting example is a combination in which the lower film 2 is a phase shift film made of metal silicide (Mo silicide), the upper film 3 is a light-shielding film made of Cr film, and the intermediate film 5 is an etching stopper film made of a metal film (metal compound film) different from that of the upper film 3; and when the lower film 2 and the upper film 3 have the same etching characteristics, a non-limiting example is a combination in which the lower film 2 is a phase shift film made of Cr film, the upper film 3 is a light-shielding film made of Cr film, and the intermediate film 5 is an etching stopper film made of a metal film (metal compound film) different from that of the upper film 3 (lower film 2).

[0056] <First etching mask forming process> Next, as shown in the cross-sectional views of Figures 5(B) and (C), similar to the process shown in Figures 1(B) and (C), a photoresist film 4 is formed on the upper layer film 3, and then the photoresist film 4 is patterned to form a first resist pattern 4a (first etching mask).

[0057] <First patterning process: Upper layer pattern formation process> 5(D), using the first resist pattern 4a as an etching mask, the upper layer film 3 is selectively etched with respect to the intermediate film 5 to expose the surface of the intermediate film 5, and the sidewall surface of the upper layer film 3 is side-etched to form an upper layer pattern 3a. The sidewall surface 3s of the upper layer pattern 3a is recessed by a predetermined amount D from the sidewall surface 4s of the first resist pattern 4a. The etching is performed by isotropic etching, preferably wet etching, but may be dry etching. As the etchant, a known etchant may be used. In this step, since the surface of the underlayer film 2 is covered with the intermediate film 5, the underlayer film 2 is not etched.

[0058] <Second Etching Mask Forming Process> Next, as shown in the cross-sectional view of Fig. 6(A), the first resist pattern 4a is deformed by a reflow process to form a second resist pattern 4b (second etching mask) in the same manner as in the process shown in Fig. 2(B). The second resist pattern 4b covers the sidewall surface 3s of the upper layer pattern 3a and contacts the surface 5f (intermediate layer surface) of the intermediate film 5.

[0059] <Second patterning process> - Intermediate layer pattern formation process - 6(B), the intermediate film 5 is selectively etched with respect to the lower film 2 using the second resist pattern 4b as an etching mask to form an intermediate layer pattern 5a (first intermediate layer pattern 5a). A sidewall surface 5as (first intermediate layer sidewall surface) of the intermediate layer pattern 5a is exposed. The etching may be a known wet etching, but may be a dry etching.

[0060] -Lower layer pattern formation process- 6(C), the lower layer film 2 is etched using the second resist pattern 4b as an etching mask to form a lower layer pattern 2a, so that a sidewall surface 2s of the lower layer pattern 2a is exposed. By selectively etching the lower film 2 with respect to the intermediate layer pattern 5a, recession due to side etching of the intermediate layer pattern 5a can be prevented. The etching may be a known wet etching, but may be a dry etching. In the intermediate layer pattern forming step and the lower layer pattern forming step, the upper layer pattern 3a is not etched since it is protected by the second resist pattern 4b.

[0061] The lower layer film 2 and the upper layer film 3 may be made of materials having the same etching characteristics, for example, the same substance, and the etchant used for etching the upper layer film 3 in the upper layer film patterning step may be the same as the etchant used for etching the lower layer film 2 in the lower layer film patterning step. In this case, it is possible to contribute to reducing the burden of production management. In particular, by sharing the deposition equipment and etching equipment for the lower layer film 2 and the upper layer film 3, it is possible to further reduce the burden of production management and reduce production costs.

[0062] <Etching mask removal process> Next, as shown in the cross-sectional view of FIG. 6(D), the second resist pattern 4b is removed by ashing, wet cleaning, or the like.

[0063] 6(D), the sidewall surface 3s of the upper layer pattern 3a is recessed from the sidewall surface 2s of the lower layer pattern 2a and the sidewall surface 5as of the intermediate layer pattern 5a. The sidewall surface 3s is separated from the sidewall surface 2s and the sidewall surface 5as, forming a rim portion RM of width W. The rim portion RM is composed of the lower layer pattern 2a and the intermediate layer pattern 5a, and the surface 5f of the intermediate layer pattern 5a is exposed. The rim portion RM is formed in a self-aligned manner adjacent to a laminated pattern (second laminated pattern) constituted by laminating a lower layer pattern 2a, an intermediate layer pattern 5a, and an upper layer pattern 3a. The optical characteristics of the rim portion RM are determined by the laminated structure of the lower film 2 and intermediate film 5 , and the optical characteristics of the laminated pattern, which is the transferred pattern, are determined by the laminated structure of the lower film 2 , intermediate film 5 and upper film 3 .

[0064] When the rim portion RM is used as a halftone portion, the optical characteristics of the rim portion RM can be, for example, a transmittance of 3 to 70% (3%≦transmittance≦70%) for the representative wavelength of the exposure light, and a low phase shift angle (for example, higher than 0° and less than 20°). Furthermore, when the rim portion RM is used as a phase shift portion (phase inversion portion), the optical characteristics of the rim portion RM can be set, for example, so that the transmittance for the representative wavelength of the exposure light is 3 to 50% (3%≦transmittance≦50%) and the phase shift angle (to invert the phase) is approximately 180° (160°≦phase shift amount≦200°), and more preferably 170°≦phase shift amount≦190°.

[0065] For example, the lower layer film 2 can be a phase shift film having a transmittance of 3 to 90% (phase shift angle 160° to 180°), the intermediate film 5 can be a semi-transparent film (transmittance 3% to 75%) with a low phase angle (phase shift angle 20° or less), and the rim portion RM can be a phase shift portion.

[0066] <Third patterning process> Furthermore, as shown in Figure 6(E), the upper layer pattern 3a may be used as an etching mask to selectively etch the intermediate layer pattern 5a relative to the upper layer pattern 3a and the lower layer pattern 2a to form an intermediate layer pattern 5b (second intermediate layer pattern 5b), and expose the surface 2f of the lower layer pattern 2a. The sidewall surface 3s of the upper layer pattern 3a and the sidewall surface 5bs (second intermediate layer sidewall surface) of the intermediate layer pattern 5b are spaced apart from the sidewall surface 2s, exposing the surface 2f of the lower layer pattern 2a and forming a rim portion RM of width W. The rim portion RM is composed of a single layer of the lower layer pattern 2a. Since the intermediate layer pattern 5a in the rim portion RM is removed, the optical characteristics of the rim portion RM are determined by the lower layer film 2. On the other hand, the optical characteristics of the laminated pattern, which is the transferred pattern, are determined by the laminated structure of the lower layer film 2, intermediate film 5, and upper layer film 3.

[0067] By selecting a single layer structure of the lower layer film 2 or a laminated structure of the lower layer film 2 and intermediate film 5 for the configuration of the rim portion RM, it is possible to adjust the phase shift angle (phase shift amount) and / or transmittance. The optical characteristics of the rim portion RM can be adjusted according to the customer's requests, the intended use of the photomask 100, the pattern dimensional accuracy, and the like.

[0068] The shape of the upper layer pattern 3a is not limited and may have any shape. Fig. 7 is a plan view showing an example in which the upper layer pattern 3a has an opening OP. Fig. 7(A) is a plan view in the process shown in Fig. 6(D), and Fig. 7(B) is a plan view in the process shown in Fig. 6(E). Within an opening OP of the upper layer pattern 3a, a rim portion RM having a predetermined width W is formed evenly along the inner periphery of the opening OP. A hole HL is provided within the rim portion RM, and the transparent substrate 1 is exposed within the hole HL. The rim portion RM can improve the resolution of the hole pattern of the photoresist that is the object to be exposed.

[0069] The upper layer pattern 3a may have a wiring shape, for example, in order to form a wiring pattern on the photoresist that is the object to be exposed. FIG. 8 is a cross-sectional view and a plan view showing a process of forming an upper layer pattern 3a having a wiring pattern shape.

[0070] As shown in the cross-sectional view of Figure 8(A), similar to the processes shown in Figures 5(A), (B), (C) and (D), a first resist pattern 4a (first etching mask) is formed on a transparent substrate 1 having a lower layer film 2, an intermediate film 5 and an upper layer film 3 formed thereon, and the upper layer film 3 is patterned to form an upper layer pattern 3a having a wiring shape.

[0071] Next, as shown in the cross-sectional view of Fig. 8(B), the first resist pattern 4a is heat-treated and deformed to form a second resist pattern 4b (second etching mask) in the same manner as in the process shown in Fig. 6(A). The second resist pattern 4b covers the sidewall surface 3s of the upper layer pattern 3a and contacts the surface 5f of the intermediate film 5.

[0072] Next, as shown in the cross-sectional view of Fig. 8(C) and the plan view of Fig. 8(D), similarly to the steps shown in Fig. 6(B), (C), and (D), the intermediate film 5 and the underlayer film 2 are etched using the second resist pattern 4b as an etching mask to form an intermediate layer pattern 5a (first intermediate layer pattern) and a underlayer pattern 2a. Then, the second resist pattern 4b is removed.

[0073] 8D is a plan view showing the shapes of the upper layer pattern 3a and the rim portion RM, and shows one end of the wiring pattern LN defined by the upper layer pattern 3a. The other end of the wiring pattern LN is similar. The wiring pattern LN is a laminated pattern (second laminated pattern) composed of a lower layer film 2, an intermediate film 5 and an upper layer film 3, and a rim portion RM of width W composed of the lower layer film 2 and the intermediate film 5 is formed evenly in a self-aligned manner to surround the outer periphery of the wiring pattern LN.

[0074] 9A and 9B are a cross-sectional view and a plan view that show a schematic example of a wiring pattern having a rim portion RM formed around the periphery thereof by a lower layer film 2 (lower layer pattern 2a). As shown in the cross-sectional and plan views of Figures 9(A) and (B), similar to the process shown in Figure 6(E), after the process shown in Figure 8(C), the upper layer pattern 3a may be used as an etching mask to selectively etch the intermediate layer pattern 5a with respect to the upper layer pattern 3a and the lower layer pattern 2a to form an intermediate layer pattern 5b (second intermediate layer pattern 5b) and expose the surface 2f of the lower layer pattern 2a. The wiring pattern LN is a laminated pattern composed of a lower layer 2, an intermediate film 5 and an upper layer 3, and a rim portion RM of width W composed of the lower layer 2 is formed uniformly in a self-aligned manner to surround the outer periphery of the wiring pattern LN. The wiring pattern may be straight or curved, or may be rectangular like a capacitor electrode.

[0075] In order to obtain the necessary optical characteristics of the rim portion RM, a laminated structure of the lower layer film 2 and the intermediate film 5 or a single layer structure of the lower layer film 2 can be appropriately selected as the structure of the rim portion RM.

[0076] (Embodiment 3) It is also possible to provide two types of rim portions RM in the transfer pattern. It is possible to appropriately select the rim portion RM having the optimal optical characteristics from the two types of rim portions RM according to the shape, arrangement, etc. of the transfer pattern. After the process shown in Figure 6 (D), the intermediate film 5 is removed in the desired area of ​​the rim portion RM, making it possible to mix rim portion RM consisting of a laminated structure of the lower layer film 2 and the intermediate film 5 with rim portion RM consisting of a single layer of the lower layer film 2.

[0077] FIG. 10 is a cross-sectional view showing a process of forming a pattern provided with rim portions RM having different optical characteristics by patterning the rim portions RM. Below, a method for patterning a rim portion RM formed around a wiring pattern will be explained as an example, however, this is not limited to a wiring pattern and may be a rim portion RM formed in a hole pattern, or a rim portion RM formed adjacent to a pattern of any other shape.

[0078] <Third resist pattern forming process: intermediate layer mask forming process> As shown in the cross-sectional view of Figure 10(A), after the process shown in Figure 6(D), a photoresist film 6 (second photoresist film) is formed to cover a surface 5f of the exposed intermediate layer pattern 5a (first intermediate layer pattern), which is the surface of the rim portion RM.

[0079] Thereafter, as shown in the cross-sectional view of FIG. 10(B), the photoresist film 6 is patterned by a lithography process, and then a resist pattern 6a (third resist pattern) is formed to expose a part of the surface 5f of the intermediate layer pattern 5a. As shown in FIG. 10(B), resist pattern 6a has a shape that partially covers surface 5f (rim portion RM), covering rim portion RM2 but exposing rim portion RM1. The resist pattern 6a functions as a mask (rim mask) for patterning the rim portion RM.

[0080] <Fourth patterning process: intermediate layer patterning process> Thereafter, as shown in the cross-sectional view of Figure 10(C), the intermediate layer pattern 5a is patterned using a resist pattern 6a, which is a third etching mask (intermediate layer mask), to form an intermediate layer pattern 5c (third intermediate layer pattern 5c). In addition, since the exposed intermediate layer pattern 5a of the rim portion RM1 is selectively etched with respect to the lower layer pattern 2a and the upper layer pattern 3a, the surface 2f of the lower layer pattern 2a of the rim portion RM1 is exposed. The intermediate layer pattern 5a of the rim portion RM2 covered with the resist pattern 6a is left.

[0081] <Third resist pattern removal process: intermediate layer mask removal process> Thereafter, as shown in the cross-sectional view of FIG. 10(D), the resist pattern 6a serving as an etching mask is removed by ashing, wet cleaning, or the like. Adjacent to a transfer pattern consisting of a stack of a lower layer pattern 2a, an intermediate layer pattern 5c, and an upper layer pattern 3a, a rim portion RM1 (first rim portion) and a rim portion RM2 (second rim portion) having a predetermined width W are formed.

[0082] As shown in Fig. 10(D), the rim portion RM1 (first rim portion) is composed of a single layer of the lower layer pattern 2a (lower layer film 2), and the rim portion RM2 (second rim portion) is composed of a laminate of the lower layer pattern 2a (lower layer film 2) and the intermediate layer pattern 5a, and the two types of rim portions (rim portion RM1 and rim portion RM2) have different optical properties. For example, it is possible to make one rim portion RM a phase shift region and the other rim portion RM a semi-transmitting region, or it is also possible to make each semi-transmitting region have a different transmittance. [Industrial Applicability]

[0083] According to the present invention, a method for manufacturing a photomask that can easily form a self-aligned rim portion can be provided. This method for manufacturing a photomask can be applied to various patterns and can also contribute to simplifying the photomask manufacturing process, and has high industrial applicability. [Explanation of symbols]

[0084] 1 Transparent substrate 2 Lower layer membrane 2a Lower layer pattern 2s Side wall surface (lower layer side wall surface) 2f surface (lower layer surface) 3. Upper membrane 3a Upper layer pattern 3s Side wall surface (upper layer side wall surface) 4 Photoresist film (first photoresist film) 4a First resist pattern (first etching mask) 4b Second resist pattern (second etching mask) 4s Side wall surface (resist side wall surface) 5 Interlayer 5a Intermediate layer pattern (first intermediate layer pattern) 5b Intermediate layer pattern (second intermediate layer pattern) 5as Side wall surface (first intermediate layer side wall surface) 5bs side wall surface (second intermediate layer side wall surface) 5f surface (middle layer surface) 6 Photoresist film (second photoresist film) 6a Resist pattern (third resist pattern) 10 Photomask blanks 100 Photomask RM rim section RM1 rim part (first rim part) RM2 rim part (second rim part) HL Hall OP Opening LN wiring pattern

Claims

1. A method for manufacturing a photomask having a transfer pattern, comprising: a photomask blanks preparation step of preparing a photomask blank in which an underlayer film is formed on a transparent substrate and an upper layer film is formed on the underlayer film; a first etching mask forming step of forming a first resist pattern on the upper layer film; a first patterning step of selectively etching the upper layer film with respect to the lower layer film using the first resist pattern as a mask to form an upper layer pattern; a second etching mask forming step of transforming the first resist pattern to form a second resist pattern covering a sidewall of the upper layer pattern; a second patterning step of etching the underlayer film using the second resist pattern as a mask to form an underlayer pattern; an etching mask removing step of removing the second resist pattern; Including, the transfer pattern is formed by laminating the upper layer pattern and the lower layer pattern, A method for manufacturing a photomask, comprising the steps of: forming a rim portion adjacent to the transfer pattern and consisting of only the lower layer pattern;

2. A method for manufacturing a photomask having a transfer pattern, comprising: a photomask blanks preparation step of preparing a photomask blank having a lower layer film formed on a transparent substrate, an intermediate film formed on the lower layer film, and an upper layer film formed on the intermediate film; a first etching mask forming step of forming a first resist pattern on the upper layer film; a first patterning step of selectively etching the upper layer film with respect to the intermediate film using the first resist pattern as a mask to form an upper layer pattern; a second etching mask forming step of transforming the first resist pattern to form a second resist pattern covering a sidewall of the upper layer pattern; a second patterning step of etching the intermediate film and the underlayer film using the second resist pattern as a mask to form an intermediate layer pattern and an underlayer pattern; an etching mask removing step of removing the second resist pattern; Including, the transfer pattern is formed by laminating the upper layer pattern, the intermediate layer pattern, and the lower layer pattern, A method for manufacturing a photomask, comprising the steps of: forming a rim portion adjacent to the transfer pattern and configured by laminating the intermediate layer pattern and the lower layer pattern;

3. In the second etching mask forming step, the first resist pattern is deformed by performing a heat treatment.

3. The method for producing a photomask according to claim 1 or 2.

4. The rim portion has a transmittance of 3% or more and 70% or less for the representative wavelength of the exposure light.

3. The method for producing a photomask according to claim 1 or 2.

5. The rim portion has a phase shift angle of 160° or more and 200° or less with respect to the representative wavelength of the exposure light.

3. The method for producing a photomask according to claim 1 or 2.

6. the intermediate film has etching characteristics different from those of the lower film and the upper film, The underlayer film and the overlayer film have the same etching characteristics.

3. The method for producing a photomask according to claim 2.

7. After the etching mask removing step, a third patterning step of selectively etching the intermediate layer pattern with respect to the lower layer pattern using the upper layer pattern as a mask to remove the intermediate layer pattern in the rim portion; The rim portion is formed only from the lower layer pattern.

3. The method for producing a photomask according to claim 2.

8. an intermediate layer mask forming step of forming a third resist pattern that partially covers the intermediate layer pattern after the etching mask removing step; an intermediate layer patterning step of patterning the intermediate layer pattern using the third resist pattern as a mask; an intermediate layer mask removing step of removing the third resist pattern; Including, The rim portion has a first rim portion composed of only the lower layer pattern, and a second rim portion composed of a laminate of the intermediate layer pattern and the lower layer pattern.

3. The method for producing a photomask according to claim 2.

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