Photomask blank manufacturing method and photomask manufacturing method

Abstract

To provide a manufacturing method of a photomask blank and a manufacturing method of a photomask capable of improving dimensional accuracy of a pattern in a photomask, by making it easy to control a dimension of a pattern during manufacturing a photomask.SOLUTION: In a method for manufacturing a photomask blank, a surface of a transparent substrate 3 is divided into a first pattern area and a second pattern area, a first functional film 4 is formed in the first pattern area, and a second functional film 5 is formed in the region of the second pattern to manufacture a photomask blank 2.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Phase-shift masks and half-tone masks are well-known photolithography techniques. A phase-shift mask is a photomask that has a phase-shift film on a part of a transparent substrate and has the function of improving resolution and depth of focus (DOF) by changing the phase and intensity of light that passes through this part. A half-tone mask is a photomask that has a half-tone film on a part of a transparent substrate and has the function of realizing multiple gradations of three or more levels by changing the intensity of light that passes through this part.

[0003] This type of photomask is manufactured through the following steps: i) preparing a photomask blank having a light-shielding film formed on a transparent substrate, ii) forming a resist film on the light-shielding film, iii) drawing a predetermined resist pattern on the resist film and removing unnecessary resist film by development to form the predetermined resist pattern, iv) using the resist pattern as a mask to remove exposed portions of the light-shielding film by etching, v) removing the remaining resist film, vi) forming a phase shift film or a half-tone film on the exposed portions of the transparent substrate from which the light-shielding film has been removed and on the light-shielding film, vii) forming a resist film on the phase shift film or half-tone film, viiii) drawing a predetermined resist pattern on the resist film and removing unnecessary resist film by development to form the predetermined resist pattern, ix) using the resist pattern as a mask to remove exposed portions of the phase shift film or half-tone film and exposed portions of the light-shielding film by etching, and x) removing the remaining resist film. For example, Patent Document 1 describes a method for manufacturing a photomask in which a half-tone film is formed as step vi). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-257712 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the conventional photomask manufacturing method described above, the light-shielding portion is composed of a laminated portion of a light-shielding film and a phase shift film or a halftone film. Therefore, when patterning the light-shielding portion, both the phase shift film or halftone film and the light-shielding film must be etched. However, if the etching rates of the two films are different, the amount of side etching differs between the phase shift film or halftone film and the light-shielding film. This results in edge roughness at the edge of the light-shielding portion, making it difficult to achieve the desired dimensional accuracy of the light-shielding portion (edge ​​position accuracy of the light-shielding portion relative to the transparent portion). Furthermore, the laminated portion requires longer etching time than a single layer, making it difficult to control the dimension of the light-shielding portion (edge ​​position control of the light-shielding portion relative to the transparent portion (CD (Critical Dimension) control)).

[0006] Therefore, the present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a method for manufacturing a photomask blank and a method for manufacturing a photomask that make it easy to control the dimensions of a pattern during photomask manufacturing and can improve the dimensional accuracy of the pattern in the photomask. [Means for solving the problem]

[0007] 1st The method for producing a photomask blank according to the present invention includes the steps of: A method for manufacturing a photomask blank, wherein a surface of a transparent substrate is partitioned into a first pattern region and a second pattern region, a first functional film is formed in the first pattern region, and a second functional film is formed in the second pattern region, a photomask blank preparation step of preparing a first photomask blank in which a first functional film is formed on a transparent substrate; a first patterning step of patterning a first functional film with a pattern corresponding to a region of a first pattern and removing the first functional film in a region of a second pattern; a functional film forming step of forming a second functional film on the exposed portion of the transparent substrate from which the first functional film has been removed and on the first functional film; a second patterning step of patterning the second functional film with a pattern corresponding to the region of the second pattern and removing the second functional film in the region of the first pattern. This is a method for manufacturing photomask blanks. The method for producing a photomask blank according to the second aspect of the present invention comprises: A method for manufacturing a composite photomask blank, in which the surface of a transparent substrate is partitioned into a first pattern region and a second pattern region, a first functional film is formed in the first pattern region, a second functional film is formed in the second pattern region, and the first functional film and the second functional film are formed on the transparent substrate so that their edges are in contact with each other and aligned on the same plane, comprising: a photomask blank preparation step of preparing a first photomask blank in which a first functional film is formed on a transparent substrate; a first patterning step of patterning a first functional film with a pattern corresponding to a region of a first pattern and removing the first functional film in a region of a second pattern; a functional film forming step of forming a second functional film on the exposed portion of the transparent substrate from which the first functional film has been removed and on the first functional film; a second patterning step of patterning the second functional film with a pattern corresponding to the region of the second pattern and removing the second functional film in the region of the first pattern. This is a method for manufacturing photomask blanks.

[0008] Here, as one embodiment of the method for producing a photomask blank according to the present invention, As a first photomask blank, a photomask blank is used in which a first functional film is formed on a transparent substrate, and an intermediate film having etching properties different from those of the first functional film is formed on the first functional film; The second functional film is a film having the same etching characteristics as the first functional film. The above configuration can be adopted.

[0009] in this case, The first and second functional films are made of Cr-based materials. The above configuration can be adopted.

[0010] In another aspect of the method for producing a photomask blank according to the present invention, As the first functional film, a film having a function of adjusting the optical characteristics of exposure light is used, The second functional film is a film having a function of adjusting the optical characteristics of the exposure light, which is different from the first functional film. The above configuration can be adopted.

[0011] in this case, a phase shift film or a halftone film is used as either the first functional film or the second functional film; A light-shielding film is used as either the first functional film or the second functional film. The above configuration can be adopted.

[0012] Further, a method for manufacturing a photomask according to the present invention includes the steps of: a photomask blanks preparation step of preparing a photomask blank manufactured by any one of the photomask blanks manufacturing methods described above; and a patterning step of patterning the first functional film and the second functional film into a predetermined pattern. This is a method for manufacturing a photomask. [Effects of the Invention]

[0013] According to the present invention, a composite photomask blank is manufactured in which a first functional film and a second functional film are formed on a transparent substrate so that their edges are in contact with each other and aligned on the same plane. In this photomask blank, there is no substantial laminated portion of the first functional film and the second functional film, and the edges of the photomask pattern are defined on the first functional film and the second functional film, which are essentially single layers. This means that edge roughness is less likely to occur at the edges of the photomask pattern and that etching time is shortened. Therefore, according to the present invention, it is possible to easily control the dimensions of the pattern during photomask manufacturing and improve the dimensional accuracy of the pattern in the photomask. [Brief explanation of the drawings]

[0014] [Figure 1]Fig. 1(a) is an enlarged plan view of a main part of a photomask according to one embodiment of the present invention, and Fig. 1(b) is a cross-sectional view taken along line AA in Fig. 1(a). [Figure 2] Fig. 2(a) is an enlarged plan view of a main portion of a photomask blank according to one embodiment of the present invention, which is the basis of the photomask in Fig. 1. Fig. 2(b) is a cross-sectional view taken along line BB in Fig. 2(a). [Figure 3] 3(a) to 3(d) are explanatory diagrams of a method for manufacturing a photomask blank according to the first embodiment of the present invention. [Figure 4] 4(a) to 4(c) are explanatory diagrams continuing from FIG. [Figure 5] 5(a) to 5(d) are explanatory diagrams continuing from FIG. [Figure 6] 6(a) to 6(d) are explanatory diagrams continuing from FIG. [Figure 7] 7(a) to 7(d) are explanatory diagrams of a method for manufacturing a photomask blank according to the second embodiment of the present invention. [Figure 8] 8(a) to 8(c) are explanatory diagrams continuing from FIG. [Figure 9] 9(a) to 9(d) are explanatory diagrams continuing from FIG. [Figure 10] 10(a) to 10(d) are explanatory diagrams continuing from FIG. [Figure 11] 11(a) to 11(d) are explanatory diagrams of a method for manufacturing a photomask blank according to the third embodiment of the present invention. [Figure 12] 12(a) and 12(b) are explanatory diagrams continuing from FIG. [Figure 13] 13(a) to 13(d) are explanatory diagrams continuing from FIG. [Figure 14] 14(a) to 14(c) are explanatory diagrams continuing from FIG. [Figure 15] 15(a) to 15(d) are explanatory diagrams of a method for manufacturing a photomask according to one embodiment of the present invention. [Figure 16] 16(a) to 16(d) are explanatory diagrams continuing from FIG. [Figure 17] 17(a) to 17(d) are supplementary explanatory diagrams for step 3 in FIG. 15(c). [Figure 18] FIG. 18 is a partially enlarged cross-sectional view of FIG. 1(b) and FIG. 16(d). [Figure 19] 19(a) to 19(d) are explanatory diagrams of a method for manufacturing a photomask blank according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] <Photomask configuration> First, the configuration of a photomask according to one embodiment of the present invention will be described.

[0016] 1, photomask 1 is a three-tone multi-level photomask having a transparent portion (white portion), a semi-transparent portion (hatched portion), and a light-shielding portion (black portion). The transparent portion is made up of a transparent substrate 3, the semi-transparent portion is made up of a semi-transparent film 4, and the light-shielding portion is made up of a light-shielding film 5. That is, the exposed portion of transparent substrate 3 on which the semi-transparent film 4 and the light-shielding film 5 are not laminated is the transparent portion, the portion where the semi-transparent film 4 is laminated on transparent substrate 3 is the semi-transparent portion, and the portion where the light-shielding film 5 is laminated on transparent substrate 3 is the light-shielding portion.

[0017] The semi-transmitting portion is formed in the form of an island pattern in which unit elements (islands) of a predetermined shape (rectangular in this embodiment) are two-dimensionally arranged at predetermined intervals. The light-shielding portion is formed so as to fill the area other than the semi-transmitting portion. The transmissive portion is formed in the form of a hole pattern 7 in which unit elements (holes 7A, 7B) of a predetermined shape (rectangular in this embodiment) are two-dimensionally arranged at predetermined intervals and within the semi-transmitting portion area and the light-shielding portion area.

[0018] The transparent substrate 3 is a substrate made of synthetic quartz glass or the like. The transparent substrate 3 has a transmittance of 95% or more for a representative wavelength (for example, i-line, h-line, or g-line) contained in the exposure light used in the exposure step using the photomask 1. The exposure light may be, for example, i-line, h-line, or g-line, or may be a mixed light containing at least two of these rays. Alternatively, the exposure light may have a wavelength band shifted or expanded to the shorter and / or longer wavelength side compared to these rays. As an example, the wavelength band of the exposure light may be expanded from a broadband of 365 nm to 436 nm to 300 nm to 450 nm. However, the exposure light is not limited to these.

[0019] The semi-transmitting film 4 is made of a Cr-based material, among known materials such as Cr or Cr-based compounds, Ni or Ni-based compounds, Ti or Ti-based compounds, Si-based compounds, and metal silicide compounds. In this embodiment, a Cr-based compound is used for the semi-transmitting film 4. The semi-transmitting film 4 is a phase shift film. Alternatively, the semi-transmitting film 4 may be a half-tone film. The semi-transmitting film 4 has a transmittance lower than that of the transparent substrate 3 and higher than that of the light-shielding film 5 for the representative wavelength contained in the exposure light, and is set to have a transmittance of 5% to 70% for the representative wavelength. The semi-transmitting film 4 may be a semi-transmitting metal film whose transmittance distribution within the plane of the photomask 1 is improved by adjusting the nitrogen content. The semi-transmitting film 4 can also contain other elements to change the optical density (OD value) of the semi-transmitting portion. The semi-transmitting film 4 is formed on the transparent substrate 3 by a method such as sputtering or vapor deposition.

[0020] The light-shielding film 5 is made of the same material as the semi-transparent film 4. In this embodiment, a Cr-based compound is used for the light-shielding film 5. The light-shielding film 5 has a transmittance of 1% or less for the representative wavelength contained in the exposure light. Alternatively, the optical density (OD value) in the light-shielding portion may be 2.7 or more. As an example, the light-shielding film 5 has a laminated structure including a first film layer and a second film layer. The first film layer is made of a Cr film and has the purpose of light-shielding. The second film layer is made of a chromium oxide film and has the purpose of anti-reflection. In this case, even if the transmittance of the first film layer is higher than 1%, it is sufficient as long as the laminated transmittance of the first film layer and the second film layer is 1% or less. The light-shielding film 5 is formed on the transparent substrate 3 by a sputtering method, a vapor deposition method, or the like.

[0021] The semi-transparent film 4 and the light-shielding film 5 are made of the same material and therefore have the same etching characteristics. However, the semi-transparent film 4 and the light-shielding film 5 are made of different materials from the intermediate film 6 described below and therefore have different etching characteristics. In other words, the semi-transparent film 4 and the light-shielding film 5 have etching selectivity relative to the intermediate film 6, and the intermediate film 6 has etching selectivity relative to the semi-transparent film 4 and the light-shielding film 5.

[0022] <Photomask blank configuration> Next, the configuration of a photomask blank according to one embodiment of the present invention, which is the basis of the photomask 1, will be described.

[0023] As shown in Fig. 2, the photomask blank 2 is in a state before the hole pattern 7 of the photomask 1 is formed. That is, the photomask blank 2 is formed so that the semi-transmitting film 4 and the light-shielding film 5 are arranged on the same plane with their edges in contact with each other, without having any transparent portions on the entire surface (effective area) of the transparent substrate 3. Note that although they are on the same plane, the film thicknesses of the semi-transmitting film 4 and the light-shielding film 5 do not necessarily have to be the same. For example, it is possible that the film thickness of the semi-transmitting film 4 is smaller than the film thickness of the light-shielding film 5, or vice versa.

[0024] <First manufacturing method of photomask blanks> Next, a method for manufacturing the photomask blanks 2 according to the first embodiment of the present invention (a first method for manufacturing the photomask blanks 2) will be described.

[0025] In general, this manufacturing method is a method for manufacturing a photomask blank 2 in which the surface of a transparent substrate 3 is partitioned into a first pattern region and a second pattern region, a first functional film is formed in the first pattern region, and a second functional film is formed in the second pattern region, wherein the first pattern region is a region of a semi-transparent film 4, the second pattern region is a region of a light-shielding film 5, the first functional film is the semi-transparent film 4, and the second functional film is the light-shielding film 5. Note that the functional film refers to a film that has the function of adjusting the optical properties of exposure light. Examples of functional films include a phase shift film that has the function of changing the phase of exposure light, a semi-transparent film that has the function of adjusting the transmittance of exposure light, and a light-shielding film that has the function of blocking exposure light.

[0026] Specifically, the production method includes: i) Photomask blank preparation process (process 1) ii) Resist film formation process (process 2) iii) Drawing process (process 3) iv) Development process (Step 4) v) Intermediate film etching process (process 5) vi) Semi-transparent film etching process (process 6) vii) Resist film removal process (process 7) viii) Light shielding film formation process (process 8) ix) Resist film formation process (process 9) x) Drawing process (Step 10) xi) Development process (Step 11) xii) Light-shielding film etching step (step 12) xiii) Intermediate film etching process (process 13) xiv) Resist film removal step (step 14) xv) Finishing process (process 15) Equipped with.

[0027] The steps from the resist film forming step (step 2) to the resist film removing step (step 7) and the steps from the resist film forming step (step 9) to the resist film removing step (step 14) are referred to as patterning steps, respectively. In the former patterning step, the semi-transparent film 4 of the photomask blanks 2 is patterned, and in the latter patterning step, the light-shielding film 5 of the photomask blanks 2 is patterned.

[0028] In the photomask blank preparation step (step 1), as shown in FIG. 3(a), a semi-transparent film 4 is formed on a transparent substrate 3, and an intermediate film (etching stopper film) 6 is formed on the semi-transparent film 4, thereby preparing a photomask blank (first photomask blank) in which the semi-transparent film 4 and the intermediate film 6 are laminated on the transparent substrate 3. A non-Cr-based material is used for the intermediate film 6. In this embodiment, Ni, Ti, or a molybdenum silicide compound is used for the intermediate film 6. The semi-transparent film 4 and the intermediate film 6 are each formed by a sputtering method, a vapor deposition method, or the like.

[0029] In the first resist film formation step (step 2), as shown in Fig. 3(b), a resist is uniformly applied onto the intermediate film 6 to form a resist film 8. The resist is applied by a coating method or a spray method.

[0030] In the first writing step (step 3), as shown in FIG. 3(c), exposure light is irradiated onto the resist film 8 using an electron beam or laser of a writing device, and a resist pattern corresponding to the region of the semi-transparent film 4 of the photomask blanks 2 is written. In addition to writing the resist pattern, the first writing step (step 3) also writes marks (alignment marks) for aligning the writing position in the second writing step (step 10). Although not shown, the alignment marks are formed, for example, at appropriate three or four locations in the surrounding region surrounding the resist pattern.

[0031] In the first development step (step 4), as shown in FIG. 3(d), unnecessary resist film 8 (portion 8a) is removed by development, forming a resist pattern. Development is performed by immersion in a developer. The drawing step (step 3) and development step (step 4) are collectively referred to as the resist pattern formation step.

[0032] In the intermediate film etching step (step 5), as shown in FIG. 4(a), the exposed portion of the intermediate film 6 is removed by etching using the resist pattern as an etching mask. Either dry etching or wet etching may be used, but wet etching is preferred for large-sized photomasks. An etching solution or etching gas is used as the etchant. Whichever etchant is used, an etchant that has etching selectivity for the intermediate film 6 (an etchant that does not etch the semi-transparent film 4) is used.

[0033] In the semi-transparent film etching step (step 6), as shown in FIG. 4(b), the exposed portion of the semi-transparent film 4 is etched away using the intermediate film 6 as an etching mask. Either dry etching or wet etching may be used, but wet etching is preferred for large photomasks. An etchant may be an etching solution or an etching gas. Either etchant must have etching selectivity for the semi-transparent film 4 (i.e., it does not etch the intermediate film 6).

[0034] In the first resist film removal step (step 7), the resist film 8 is removed as shown in Fig. 4(c) The resist film 8 is removed by ashing or by immersion in a resist stripping solution.

[0035] In the light-shielding film forming step (step 8), as shown in Fig. 5(a), a light-shielding film 5 is formed on the exposed portion of the transparent substrate 3 from which the semi-transparent film 4 has been removed and on the semi-transparent film 4. The light-shielding film 5 is formed by a sputtering method, a vapor deposition method, or the like.

[0036] In the second resist film formation step (step 9), similarly to the first resist film formation step (step 2), as shown in Fig. 5(b), resist is applied onto the light-shielding film 5 to form a resist film 8. The resist is applied by a coating method or a spray method.

[0037] In the second writing step (step 10), similarly to the first writing step (step 3), as shown in FIG. 5(c), exposure light is irradiated onto the resist film 8 using an electron beam or laser of a writing device, and a resist pattern corresponding to the region of the light-shielding film 5 of the photomask blanks 2 is written. The writing device is the same device as that used in the first writing step (step 3). In the second writing step (step 10), the writing device detects the alignment mark formed in the first writing step (step 3) and aligns the transparent substrate 3.

[0038] However, even if the alignment accuracy is improved, it is very difficult to completely eliminate misalignment. Therefore, in the second drawing process (process 10), a resist pattern is set that takes misalignment into consideration. Specifically, by offsetting (+offsetting) the edge of the light-shielding film 5 of the photomask blank 2 outward, a resist pattern is set that laps (overlaps) the edge of the laminated portion of the semi-transparent film 4, intermediate film 6, and light-shielding film 5 by an lap amount L. The lap amount L is, for example, a value of 0.3 μm or more and 0.5 μm or less.

[0039] In the second developing step (step 11), as in the first developing step (step 4), the unnecessary resist film 8 (portion 8a) is removed by development to form a resist pattern, as shown in FIG. 5(d). Development is performed by immersion in a developer. The drawing step (step 10) and the developing step (step 11) are collectively referred to as the resist pattern formation step.

[0040] In the light-shielding film etching step (step 12), as shown in FIG. 6(a), the exposed portion of the light-shielding film 5 is removed by etching using the resist pattern as an etching mask. The etching may be either dry etching or wet etching, but wet etching is preferred for large-sized photomasks. An etching solution or etching gas is used as the etchant. Whichever etchant is used, an etchant that has etching selectivity for the light-shielding film 5 (an etchant that does not etch the intermediate film 6) is used.

[0041] In the intermediate film etching step (step 13), as shown in FIG. 6(b), the exposed portion of the intermediate film 6 is removed by etching using the light-shielding film 5 (or a resist pattern if the light-shielding film 5 does not remain) as an etching mask. The etching may be either dry etching or wet etching, but wet etching is preferred for large-sized photomasks. An etching solution or etching gas is used as the etchant. Whichever etchant is used, an etchant that has etching selectivity for the intermediate film 6 (an etchant that does not etch the semi-transparent film 4) is used.

[0042] In the second resist film removal step (step 14), the resist film 8 is removed as shown in Fig. 6(c) in the same manner as in the first resist film removal step (step 7). The resist film 8 is removed by ashing or immersion in a resist stripper.

[0043] In the finishing step (step 15), as shown in FIG. 6(d), residues 9 of the intermediate film 6 and light-shielding film 5 remaining due to the lapping are removed. The residues 9 are narrow and have low rigidity, and can be easily removed by cleaning or the like. Alternatively, if the light-shielding film 5 is side-etched in the light-shielding film etching step (step 12) and the intermediate film 6 is side-etched in the intermediate film etching step (step 13), and thus no residues 9 remain, the finishing step (step 15) is not necessary.

[0044] Through the above steps 1 to 15, a photomask blank 2, which is a secondary photomask blank, is completed.

[0045] <Second method for manufacturing photomask blanks> Next, a method for manufacturing the photomask blanks 2 according to the second embodiment of the present invention (a second method for manufacturing the photomask blanks 2) will be described.

[0046] In general, the manufacturing method is a method for manufacturing a photomask blank 2 in which the surface of a transparent substrate 3 is partitioned into a first pattern region and a second pattern region, a first functional film is formed in the first pattern region, and a second functional film is formed in the second pattern region, wherein the first pattern region is a region of a light-shielding film 5, the second pattern region is a region of a semi-transparent film 4, the first functional film is the light-shielding film 5, and the second functional film is the semi-transparent film 4.

[0047] Specifically, the production method includes: i) Photomask blank preparation process (process 1) ii) Resist film formation process (process 2) iii) Drawing process (process 3) iv) Development process (Step 4) v) Intermediate film etching process (process 5) vi) Light-shielding film etching process (process 6) vii) Resist film removal process (process 7) viii) Semi-permeable membrane formation process (Step 8) ix) Resist film formation process (process 9) x) Drawing process (Step 10) xi) Development process (Step 11) xii) Semi-transparent film etching process (process 12) xiii) Intermediate film etching process (process 13) xiv) Resist film removal step (step 14) xv) Finishing process (process 15) Equipped with.

[0048] The steps from the resist film forming step (step 2) to the resist film removing step (step 7) and the steps from the resist film forming step (step 9) to the resist film removing step (step 14) are referred to as patterning steps. In the former patterning step, the light-shielding film 5 of the photomask blanks 2 is patterned, and in the latter patterning step, the semi-transparent film 4 of the photomask blanks 2 is patterned.

[0049] The second manufacturing method differs from the first manufacturing method in that, in the first manufacturing method, the semi-transparent film 4 is patterned first and the light-shielding film 5 is patterned later, whereas in the second manufacturing method, the light-shielding film 5 is patterned first and the semi-transparent film 4 is patterned later. Apart from this, the two methods are the same. Therefore, in the following, only the differences will be described, and the same points will not be described again, as they are the same as those described in the first manufacturing method.

[0050] In the photomask blank preparation process (step 1), as shown in FIG. 7(a), a light-shielding film 5 is formed on a transparent substrate 3, and an intermediate film (etching stopper film) 6 is formed on the light-shielding film 5, thereby preparing a photomask blank (first photomask blank) in which the light-shielding film 5 and the intermediate film 6 are stacked on the transparent substrate 3.

[0051] In the first writing step (step 3), a resist pattern corresponding to the region of the light-shielding film 5 of the photomask blanks 2 is written, as shown in FIG. 7(c).

[0052] In the intermediate film etching step (step 5), as shown in Fig. 8(a), the exposed portion of the intermediate film 6 is removed by etching using the resist pattern as an etching mask. An etchant having etching selectivity for the intermediate film 6 (an etchant that does not etch the light-shielding film 5) is used.

[0053] In the light-shielding film etching step (step 6), as shown in Fig. 8(b), the exposed portion of the light-shielding film 5 is removed by etching using the intermediate film 6 as an etching mask. An etchant having etching selectivity for the light-shielding film 5 (an etchant that does not etch the intermediate film 6) is used.

[0054] In the semi-transparent film forming step (step 8), as shown in FIG. 9(a), a semi-transparent film 4 is formed on the exposed portion of the transparent substrate 3 from which the light-shielding film 5 has been removed and on the light-shielding film 5.

[0055] In the second writing step (step 10), as shown in Fig. 9(c), a resist pattern corresponding to the region of the semi-transparent film 4 of the photomask blank 2 is written. However, the resist pattern is a resist pattern that laps (overlaps) the edge of the laminated portion of the light-shielding film 5, intermediate film 6, and semi-transparent film 4 by an lap amount L by offsetting (+offsetting) the edge of the semi-transparent film 4 of the photomask blank 2 outward.

[0056] In the semi-transparent film etching step (step 12), as shown in Fig. 10(a), the exposed portion of the semi-transparent film 4 is removed by etching using the resist pattern as an etching mask. An etchant having etching selectivity for the semi-transparent film 4 (an etchant that does not etch the intermediate film 6) is used.

[0057] In the intermediate film etching step (step 13), as shown in FIG. 10(b), the exposed portion of the intermediate film 6 is removed by etching using the semi-transparent film 4 (or a resist pattern if the semi-transparent film 4 does not remain) as an etching mask. An etchant having etching selectivity for the intermediate film 6 (an etchant that does not etch the light-shielding film 5) is used.

[0058] <Third method for manufacturing photomask blanks> Next, a method for manufacturing the photomask blanks 2 according to the third embodiment of the present invention (a third method for manufacturing the photomask blanks 2) will be described.

[0059] In general, the manufacturing method is a method for manufacturing a photomask blank 2 in which the surface of a transparent substrate 3 is partitioned into a first pattern region and a second pattern region, a first functional film is formed in the first pattern region, and a second functional film is formed in the second pattern region, wherein the first pattern region is a region of a semi-transparent film 4, the second pattern region is a region of a light-shielding film 5, the first functional film is the semi-transparent film 4, and the second functional film is the light-shielding film 5.

[0060] Specifically, the production method includes: i) Photomask blank preparation process (process 1) ii) Resist film formation process (process 2) iii) Drawing process (process 3) iv) Development process (Step 4) v) Semi-transparent film etching process (process 5) vi) Resist film removal process (process 6) vii) Light shielding film formation process (process 7) viii) Resist film formation process (process 8) ix) Drawing process (process 9) x) Development process (Step 10) xi) Light-shielding film etching process (process 11) xii) Resist film removal step (step 12) xiii) Finishing process (process 13) Equipped with.

[0061] The steps from the resist film forming step (step 2) to the resist film removing step (step 6) and the steps from the resist film forming step (step 8) to the resist film removing step (step 12) are referred to as patterning steps, respectively. In the former patterning step, the semi-transparent film 4 of the photomask blanks 2 is patterned, and in the latter patterning step, the light-shielding film 5 of the photomask blanks 2 is patterned.

[0062] The third manufacturing method differs from the first manufacturing method in that: i) the first photomask blank is a photomask blank in which no intermediate film 6 is laminated, and only the semi-transparent film 4 is formed on the transparent substrate 3; and accordingly, the intermediate film etching steps (step 5) and (step 13) of the first manufacturing method are omitted; and ii) either the semi-transparent film 4 or the light-shielding film 5 is made of, for example, a Cr-based material, while the other is made of a non-Cr-based material. As a result, the semi-transparent film 4 and the light-shielding film 5 are made of different materials, resulting in different etching characteristics. As a result, different etchants are used. Except for these related points, the two methods are the same. Therefore, the third manufacturing method is similar to the first manufacturing method and will not be described further.

[0063] <Fourth method for manufacturing photomask blanks> Next, a method for manufacturing the photomask blanks 2 according to the fourth embodiment of the present invention (fourth method for manufacturing the photomask blanks 2) will be described.

[0064] In general, the manufacturing method is a method for manufacturing a photomask blank 2 in which the surface of a transparent substrate 3 is partitioned into a first pattern region and a second pattern region, a first functional film is formed in the first pattern region, and a second functional film is formed in the second pattern region, wherein the first pattern region is a region of a light-shielding film 5, the second pattern region is a region of a semi-transparent film 4, the first functional film is the light-shielding film 5, and the second functional film is the semi-transparent film 4.

[0065] Specifically, the production method includes: i) Photomask blank preparation process (process 1) ii) Resist film formation process (process 2) iii) Drawing process (process 3) iv) Development process (Step 4) v) Light-shielding film etching process (process 5) vi) Resist film removal process (process 6) vii) Semi-permeable membrane formation process (process 7) viii) Resist film formation process (process 8) ix) Drawing process (process 9) x) Development process (Step 10) xi) Semi-transparent film etching process (step 11) xii) Resist film removal step (step 12) xiii) Finishing process (process 13) Equipped with.

[0066] The steps from the resist film forming step (step 2) to the resist film removing step (step 6) and the steps from the resist film forming step (step 8) to the resist film removing step (step 12) are referred to as patterning steps, respectively. In the former patterning step, the light-shielding film 5 of the photomask blanks 2 is patterned, and in the latter patterning step, the semi-transparent film 4 of the photomask blanks 2 is patterned.

[0067] The fourth manufacturing method differs from the third manufacturing method in that, in the third manufacturing method, the semi-transparent film 4 is patterned first and the light-shielding film 5 is patterned later, whereas in the fourth manufacturing method, the light-shielding film 5 is patterned first and the semi-transparent film 4 is patterned later. Except for the relevant points, the two methods are the same. Therefore, the description of the fourth manufacturing method is omitted as it is the same as the descriptions of the first and second manufacturing methods.

[0068] <Photomask manufacturing method> Next, a method for manufacturing the photomask 1 according to one embodiment of the present invention will be described.

[0069] The manufacturing method includes: i) Photomask blank preparation process (process 1) ii) Resist film formation process (process 2) iii) Drawing process (process 3) iv) Development process (Step 4) v) Film etching step (step 5) vi) Resist film removal process (process 6) Equipped with.

[0070] The steps from the resist film forming step (step 2) to the resist film removing step (step 7) are referred to as the patterning step. In the patterning step, the transparent portion of the photomask 1 is patterned.

[0071] In the photomask blanks preparation step (step 1), as shown in FIG. 15(a), a photomask blanks 2 (secondary photomask blanks) manufactured by any of the above-mentioned methods for manufacturing photomask blanks 2 is prepared.

[0072] 15(b), in the resist film forming step (step 2), a resist is uniformly applied onto the semi-transparent film 4 and the light-shielding film 5 to form a resist film 8. The resist is applied by a coating method or a spray method.

[0073] In the drawing process (step 3), as shown in Figure 15(c), exposure light is irradiated onto the resist film 8 using an electron beam or laser of a drawing device, and a resist pattern corresponding to the area of ​​the transparent part (hole pattern 7) of the photomask 1 is drawn.

[0074] However, if the semi-transparent film 4 and the light-shielding film 5 have the same etching characteristics but different etching rates, a difference in the amount of side etching occurs between the semi-transparent film 4 and the light-shielding film 5 in the film etching step (step 5). As a result, the dimensional accuracy (edge ​​position accuracy of at least one of the semi-transparent and light-shielding portions of the photomask 1 relative to the transparent portion) of at least one of the holes 7A,... located in the semi-transparent portion area or the holes 7B,... located in the light-shielding portion area of ​​the hole pattern 7 of the photomask 1 deteriorates. Therefore, in the drawing step (step 3), a resist pattern is set taking into account the difference in etching rate. Specifically, for example, if the etching rate of the semi-transparent film 4 is higher than that of the light-shielding film 5, the holes 7A, 7B shown in Figures 17(a) and (b) have their original dimensions, but a resist pattern is set such that the edges of the holes 7A, ... located within the semi-transparent region are offset inward (-offset) as shown in Figure 17(c), or the edges of the holes 7B, ... located within the light-shielding region are offset outward (+offset) as shown in Figure 17(d). Of course, if the etching rates of the semi-transparent film 4 and the light-shielding film 5 are the same or similar, the offset process is not necessary.

[0075] As another method for controlling the etching rate, a method can be adopted in which the semi-transparent film 4 and the light-shielding film 5 are formed (deposited) so that the etching rates of the semi-transparent film 4 and the light-shielding film 5 are the same or similar. This involves changing the composition ratio of the compounds contained in the semi-transparent film 4 in the thickness direction during the manufacturing stage of the photomask blanks 2, and adjusting the etching rate by the composition gradient. For example, a method can be used in which the etching rate is slowed by increasing the etching difficulty in the direction in which etching progresses in the thickness direction. Alternatively, the opposite adjustment method can also be used.

[0076] In the developing step (step 4), as shown in FIG. 15(d), unnecessary resist film 8 (portion 8a) is removed by development to form a resist pattern. Development is performed by immersion in a developer. The drawing step (step 3) and the developing step (step 4) are collectively referred to as the resist pattern forming step.

[0077] In the film etching step (step 5), as shown in Fig. 16(a), the exposed portions of the semi-transparent film 4 and the light-shielding film 5 are removed by etching using the resist pattern as an etching mask. Either dry etching or wet etching may be used for the etching, but wet etching is preferred for large-sized photomasks. An etching solution or etching gas is used as the etchant.

[0078] However, in the case of photomask blanks 2 manufactured by the third and fourth manufacturing methods of the photomask blanks 2, the semi-transparent film 4 and the light-shielding film 5 have different etching characteristics and use different etchants, so the film etching step (step 5) is divided into a semi-transparent film etching step (step 5-1) shown in Fig. 16(b) and a light-shielding film etching step (step 5-2) shown in Fig. 16(c). The order of these steps does not matter.

[0079] In the resist film removal step (step 6), the resist film 8 is removed as shown in Fig. 16(d). The resist film 8 is removed by ashing or by immersion in a resist stripping solution.

[0080] Through the above steps 1 to 6, the photomask 1 is completed.

[0081] <Effects of the embodiment> According to each of the above-described methods for manufacturing a photomask blank 2, a composite photomask blank 2 is manufactured in which a semi-transmitting film 4 and a light-shielding film 5 are formed on a transparent substrate 3 so that their edges are in contact with each other and aligned on the same plane. That is, a photomask blank 2 having two regions with different optical properties is manufactured. In this photomask blank 2, there is no substantial laminated portion of the semi-transmitting film 4 and the light-shielding film 5, and the edges of the pattern of the photomask 1 are defined on the semi-transmitting film 4 and the light-shielding film 5, which are essentially single layers. That is, the pattern of the photomask 1 is patterned on a photomask blank 2 having a small overall film thickness and a small aspect ratio (ratio of pattern dimension to height). This means that edge roughness is less likely to occur at the edges of the pattern of the photomask 1 and that the etching time is shortened. This facilitates dimensional control of the pattern during manufacturing of the photomask 1, and improves the dimensional accuracy of the pattern in the photomask 1.

[0082] 18, the semi-transmitting film 4 and the light-shielding film 5 are each substantially a single layer, and the holes 7A, ... of the hole pattern 7 of the photomask 1 are formed in the region of the semi-transmitting film 4, and the holes 7B, ... are formed in the region of the light-shielding film 5. Therefore, in the photomask 1, the dimension SA of each hole 7A and the dimension SB of each hole 7B are finished faithfully to the design. This makes it possible to improve the dimensional accuracy of each hole 7A, 7B compared to when the hole pattern is formed in a laminated portion, and to pattern a highly accurate hole pattern 7 faithfully to the design.

[0083] Furthermore, according to the manufacturing method of the photomask 1, the patterning of the holes 7A, ... in the semi-transparent film 4 and the patterning of the holes 7B, ... in the light-shielding film 5 are performed in a single patterning process, rather than in separate patterning processes. Therefore, misalignment is naturally unlikely to occur, and the relative positional relationship of each hole 7A, 7B, such as the distance D between adjacent holes 7A, 7B, in the photomask 1 is finished faithful to the design. This improves the positional accuracy of each hole 7A, 7B, and in this respect, too, a highly accurate hole pattern 7 can be patterned faithful to the design.

[0084] Furthermore, according to the first and second manufacturing methods of the photomask blanks 2, films made of Cr-based materials are used as the semi-transmitting film 4 and the light-shielding film 5. Cr-based materials are resistant to high pressure and chemicals and have good film strength. Therefore, cleaning resistance equivalent to that of a general photomask can be obtained.

[0085] <Other embodiments> The present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present invention.

[0086] In the first and second manufacturing methods of the photomask blanks 2, the first and second functional films are selected to have the same etching characteristics (note that throughout this specification, when the etching characteristics are "same" or the film material is "same," this includes the concept of "approximation"). However, the present invention is not limited to this. For example, i) a first functional film having different etching characteristics from the second functional film and the intermediate film may be selected, and a second functional film having different etching characteristics from the first functional film and the intermediate film may be selected. Alternatively, ii) a first functional film having different etching characteristics from the second functional film and the intermediate film may be selected, and a second functional film having different etching characteristics from the first functional film but the same etching characteristics as the intermediate film may be selected.

[0087] Furthermore, in each of the manufacturing methods for the photomask blanks 2, the residue 9 is removed so that the laminated portion is completely eliminated. However, the present invention is not limited to this. For example, in the photomask, if the edge of the pattern does not overlap (pass through) the portion, the laminated portion 10 may remain as shown in FIG. 19. In this case, the overlap amount L is set to a large value, for example, a value of 1 μm or more and 10 μm or less. Note that FIG. 19 is a drawing corresponding to the first manufacturing method for the photomask blanks 2.

[0088] Furthermore, the photomask blank may further include a semi-transparent film having a different transmittance formed on the photomask blank 2. In this case, the transmittance of the lower semi-transparent film 4 (first semi-transparent film) is readjusted by the upper semi-transparent film (second semi-transparent film). That is, the second semi-transparent film functions as a transmittance adjusting film.

[0089] The photomask blank may also be one in which a phase shift film is formed on the photomask blank 2. In this case, the underlying semi-transparent film 4 may be set to a degree that does not affect the phase shift effect, i.e., the phase shift amount may be set to between 0 degrees and 20 degrees.

[0090] Furthermore, in the above embodiment, the pattern of the photomask 1 is a hole pattern 7. However, the hole pattern is merely an example, and the present invention is not limited thereto. The photomask pattern may be any of a variety of patterns, including a pattern in which the edges of the pattern do not pass through the boundary between the first functional film region (first pattern region) and the second functional film region (second pattern region) and are set within each of the first functional film region and the second functional film region, and a pattern in which the edges of the pattern pass through the boundary between the first functional film region and the second functional film region and are set across the first functional film region and the second functional film region.

[0091] In the above embodiment, either the first functional film or the second functional film is a semi-transparent film 4, and the other is a light-shielding film 5. However, the present invention is not limited to this. The first functional film and the second functional film can be appropriately selected from various functional films. For example, they may be phase shift films that are not used as semi-transparent films.

[0092] Furthermore, as long as there is no physical interference, it is naturally possible to apply the technical elements described above to other embodiments or examples, to replace the technical elements described above with technical elements related to other embodiments or examples, or to combine the technical elements described above, and this is naturally intended by the present invention. [Explanation of symbols]

[0093] 1...photomask, 2...photomask blank, 3...transparent substrate, 4...semi-transparent film, 5...light-shielding film, 6...intermediate film (etching stopper film), 7...hole pattern, 7A...hole in semi-transparent portion, 7B...hole in light-shielding portion, 8...resist film, 8a...portion, 9...residue, 10...laminated portion

Claims

1. A method for manufacturing a photomask blank, wherein a surface of a transparent substrate is partitioned into a first pattern region and a second pattern region, a first functional film is formed in the first pattern region, and a second functional film is formed in the second pattern region, a photomask blank preparation step of preparing a first photomask blank in which a first functional film is formed on a transparent substrate; a first patterning step of patterning a first functional film with a pattern corresponding to a region of a first pattern and removing the first functional film in a region of a second pattern; a functional film forming step of forming a second functional film on the exposed portion of the transparent substrate from which the first functional film has been removed and on the first functional film; a second patterning step of patterning the second functional film with a pattern corresponding to the region of the second pattern and removing the second functional film in the region of the first pattern. A method for manufacturing photomask blanks.

2. A method for manufacturing a composite photomask blank, in which a surface of a transparent substrate is partitioned into a first pattern region and a second pattern region, a first functional film is formed in the first pattern region, a second functional film is formed in the second pattern region, and the first functional film and the second functional film are formed on the transparent substrate so as to be aligned on the same plane with their edges in contact with each other, a photomask blank preparation step of preparing a first photomask blank in which a first functional film is formed on a transparent substrate; a first patterning step of patterning a first functional film with a pattern corresponding to a region of a first pattern and removing the first functional film in a region of a second pattern; a functional film forming step of forming a second functional film on the exposed portion of the transparent substrate from which the first functional film has been removed and on the first functional film; a second patterning step of patterning the second functional film with a pattern corresponding to the region of the second pattern and removing the second functional film in the region of the first pattern. A method for manufacturing photomask blanks.

3. The second patterning step comprises: a resist film forming step of forming a resist film on the second functional film; a resist pattern forming step of forming a resist pattern corresponding to the region of the second pattern, the resist pattern overlapping the edge portion of the laminated portion of the first functional film and the second functional film by offsetting the position of the edge of the resist pattern outward, with a predetermined overlap amount; and an etching step of removing the exposed portion of the second functional film in the region of the first pattern by etching using the resist pattern as a mask. The method for producing the photomask blanks according to claim 1 or 2.

4. The method further includes a finishing step of removing residue of the second functional film remaining due to the predetermined overlap amount. The method for producing the photomask blanks according to claim 3 .

5. As a first photomask blank, a photomask blank is used in which a first functional film is formed on a transparent substrate, and an intermediate film having etching characteristics different from those of the first functional film is formed on the first functional film, The second functional film is a film having the same etching characteristics as the first functional film. The method for manufacturing the photomask blank according to any one of claims 1 to 4.

6. The first and second functional films are made of a material selected from Cr-based, Ni-based, Ti-based, Si-based, metal silicide-based, and metals with adjusted nitrogen content. The method for producing the photomask blanks according to claim 5 .

7. As the first photomask blank, a photomask blank in which a first functional film is formed on a transparent substrate is used, The second functional film is a film having etching characteristics different from those of the first functional film. The method for manufacturing the photomask blank according to any one of claims 1 to 4.

8. As the first functional film, a film having a function of adjusting the optical characteristics of exposure light is used, The second functional film is a film having a function of adjusting the optical characteristics of the exposure light, which is different from the first functional film. The method for manufacturing the photomask blank according to any one of claims 1 to 7.

9. a phase shift film or a halftone film is used as either the first functional film or the second functional film; A light-shielding film is used as either the first functional film or the second functional film. The method for producing a photomask blank according to claim 8 .

10. Either one or both of the first functional film and the second functional film are adjusted so that the etching rate thereof is the same as that of the other of the first functional film and the second functional film. The method for manufacturing the photomask blank according to any one of claims 1 to 9.

11. a photomask blanks preparation step of preparing a photomask blank manufactured by the photomask blanks manufacturing method according to any one of claims 1 to 10; and a patterning step of patterning the first functional film and the second functional film into a predetermined pattern. A method for manufacturing a photomask.

12. The patterning process includes only one drawing step. The method for manufacturing a photomask according to claim 11 .

13. The patterning process is a resist film forming step of forming a resist film on the surface of the photomask blank; a resist pattern forming step of forming a resist pattern according to a predetermined pattern, the resist pattern taking into consideration the difference in etching rate between the first functional film and the second functional film; and an etching step of removing exposed portions of the first functional film and the second functional film by etching using the resist pattern as a mask. The method for manufacturing a photomask according to claim 11 or 12.

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