Method for manufacturing a photomask blank and method for manufacturing a photomask

Abstract

To provide a photomask blank manufacturing method and a photomask manufacturing method that can improve the dimensional accuracy of a pattern in a photomask while easily performing dimensional control of the pattern during the manufacturing of the photomask. The photomask blank manufacturing method is for manufacturing a photomask blank (2) that divides the surface of a transparent substrate (3) into a first pattern region and a second pattern region, and forms a first functional film in the first pattern region and a second functional film in the second pattern region.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a photomask preform and a method for manufacturing a photomask. Background Technology

[0002] As a photolithography technique, phase-shifting masks and halftone masks are known. A phase-shifting mask has a phase-shifting film on a portion of a transparent substrate, and it can improve resolution and depth of focus (DOF) by changing the phase and intensity of light passing through that portion. A halftone mask has a halftone film on a portion of a transparent substrate, and it can achieve multiple gray levels (three or more) by changing the intensity of light passing through that portion.

[0003] This photomask is manufactured through the following steps: i) preparing a photomask blank on a transparent substrate with a light-shielding film formed thereon; ii) forming a resist film on the light-shielding film; iii) drawing a predetermined resist pattern on the resist film, removing unwanted resist film by development, and forming a predetermined resist pattern; iv) using the resist pattern as a mask, etching away the exposed portion of the light-shielding film; v) removing the remaining resist film; vi) forming a phase-shifting film or halftone film on the exposed portion of the transparent substrate with the light-shielding film removed and on the light-shielding film; vii) forming a resist film on the phase-shifting film or halftone film; viiii) drawing a predetermined resist pattern on the resist film, removing unwanted resist film by development, and forming a predetermined resist pattern; ix) using the resist pattern as a mask, etching away the exposed portion of the phase-shifting film or halftone film and the exposed portion of the light-shielding film; x) removing the remaining resist film. For example, in Patent Document 1, as step vi), a method for manufacturing a photomask that forms a halftone film is described.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2005-257712 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] According to the conventional photomask manufacturing method described above, the light-shielding section is composed of a stack of a light-shielding film and a phase-shifting film or halftone film. Therefore, when patterning the light-shielding section, both the phase-shifting film or halftone film and the light-shielding film need to be etched. However, when the etching rates of the two are different, the lateral etching amount between the phase-shifting film or halftone film and the light-shielding film will differ. As a result, edge roughness will occur at the edges of the light-shielding section, making it difficult to achieve the expected dimensional accuracy (edge ​​position accuracy of the light-shielding section relative to the transmission section). Furthermore, since it is a stacked section, the etching time is sometimes longer than in the case of a single layer, making it difficult to control the size of the light-shielding section (edge ​​position control of the light-shielding section relative to the transmission section (CD (Critical Dimension) control)).

[0009] Therefore, the present invention was made in view of the above circumstances, and its object is to provide a method for manufacturing a photomask blank that facilitates pattern size control during photomask manufacturing and improves the dimensional accuracy of the pattern in the photomask, as well as a method for manufacturing a photomask.

[0010] Methods for solving problems

[0011] The method for manufacturing a photomask preform of the present invention comprises dividing the surface of a transparent substrate into a first patterned region and a second patterned region, forming a first functional film in the first patterned region, and forming a second functional film in the second patterned region. The method includes:

[0012] The photomask preform preparation process prepares a first photomask preform on a transparent substrate to form a first functional film; the first patterning process patterns the first functional film with a pattern corresponding to the first pattern area and removes the first functional film in the second pattern area; the functional film forming process forms a second functional film on the exposed portion of the transparent substrate with the first functional film removed and on the first functional film; the second patterning process patterns the second functional film with a pattern corresponding to the second pattern area and removes the second functional film in the first pattern area.

[0013] Here, as one embodiment of the method for manufacturing the photomask blank of the present invention, the following configuration can be adopted:

[0014] The second patterning process includes: a resist film forming process, in which a resist film is formed on the second functional film; a resist patterning process, in which the edge position of the resist pattern is offset outward to form a resist pattern that overlaps the edge portion of the stacked portion of the first functional film and the second functional film with a predetermined overlap amount, wherein the resist pattern corresponds to the second pattern area; and an etching process, in which the resist pattern is used as a mask to remove the exposed portion of the second functional film in the first pattern area by etching.

[0015] In this case, the following configuration can be adopted:

[0016] It also includes a finishing process to remove residues from the secondary functional membrane that remain due to the specified amount of overlap.

[0017] Furthermore, as another embodiment of the method for manufacturing the photomask blank of the present invention, the following configuration may be adopted:

[0018] As the first photomask preform, a photomask preform on which a first functional film is formed on a transparent substrate and an intermediate film having different etching characteristics from the first functional film is formed on the first functional film; as the second functional film, a film having the same etching characteristics as the first functional film is used.

[0019] In this case, the following configuration can be adopted:

[0020] As the first functional membrane and the second functional membrane, membranes made of materials selected from Cr-based, Ni-based, Ti-based, Si-based, metal silicides, and metals with adjusted nitrogen content are used.

[0021] Furthermore, as another embodiment of the method for manufacturing the photomask blank of the present invention, the following configuration may be adopted:

[0022] As the first photomask preform, a photomask preform on which a first functional film is formed on a transparent substrate is used; as the second functional film, a film having different etching characteristics than the first functional film is used.

[0023] Furthermore, as another embodiment of the method for manufacturing the photomask blank of the present invention, the following configuration may be adopted:

[0024] As the first functional film, a film with the function of adjusting the optical properties of exposure light is used; as the second functional film, a film with the function of adjusting the optical properties of exposure light, but with a function different from that of the first functional film, is used.

[0025] In this case, the following configuration can be adopted:

[0026] A phase-shifting film or a halftone film is used as either the first or the second functional film; a light-shielding film is used as the other of the first or the second functional film.

[0027] Furthermore, as another embodiment of the method for manufacturing the photomask blank of the present invention, the following configuration may be adopted:

[0028] Adjust either or both of the first functional film or the second functional film so that their etching rate is the same as that of either the first functional film or the second functional film.

[0029] Furthermore, the method for manufacturing the photomask of the present invention includes:

[0030] The photomask preparation process prepares a photomask blank to be manufactured by any of the above-mentioned photomask blank manufacturing methods; the patterning process patterns the first functional film and the second functional film with a specified pattern.

[0031] Here, as one embodiment of the photomask manufacturing method of the present invention, the following configuration can be adopted:

[0032] The composition process includes a single drawing process.

[0033] Furthermore, as another embodiment of the photomask manufacturing method of the present invention, the following configuration may be adopted:

[0034] The patterning process includes: a resist film formation process, in which a resist film is formed on the surface of a photomask blank; a resist patterning process, in which a resist pattern is formed that takes into account the difference in etching rates of the first functional film and the second functional film, wherein the resist pattern is a predetermined pattern; and an etching process, in which the resist pattern is used as a mask to remove the exposed portions of the first functional film and the second functional film by etching.

[0035] Invention Effects

[0036] According to the present invention, a composite photomask preform can be manufactured on a transparent substrate in which a first functional film and a second functional film are arranged in a coplanar manner with their edges adjacent to each other. In this photomask preform, there is no substantial stacking of the first and second functional films; the pattern edges of the photomask are defined on the first and second functional films, which are essentially single layers. This means that edge roughness is less likely to occur at the edges of the photomask pattern, and the etching time is shortened. Therefore, according to the present invention, pattern size control is easier during photomask manufacturing, and the dimensional accuracy of the pattern in the photomask can be improved. Attached Figure Description

[0037] Figure 1 (a) is an enlarged top view of the main part of a photomask according to an embodiment of the present invention. Figure 1 (b) is Figure 1 (a) Sectional view along line AA.

[0038] Figure 2 (a) is a photomask preform according to one embodiment of the present invention, which is to become Figure 1 A magnified top view of the main part of the photomask blank, which forms the basis of the photomask. Figure 2 (b) is Figure 2 (a) BB line section view.

[0039] Figure 3 (a) to (d) are explanatory diagrams of the manufacturing method of the photomask blank according to Embodiment 1 of the present invention.

[0040] Figure 4 (a)~(c) are the next Figure 3 Explanatory diagram.

[0041] Figure 5 (a)~(d) are the next Figure 4 Explanatory diagram.

[0042] Figure 6 (a)~(d) are the next Figure 5 Explanatory diagram.

[0043] Figure 7 (a) to (d) are explanatory diagrams of the manufacturing method of the photomask blank according to Embodiment 2 of the present invention.

[0044] Figure 8 (a)~(c) are the next Figure 7 Explanatory diagram.

[0045] Figure 9 (a)~(d) are the next Figure 8 Explanatory diagram.

[0046] Figure 10 (a)~(d) are the next Figure 9 Explanatory diagram.

[0047] Figure 11 (a) to (d) are explanatory diagrams of the manufacturing method of the photomask blank according to Embodiment 3 of the present invention.

[0048] Figure 12 (a)~(b) are following Figure 11 Explanatory diagram.

[0049] Figure 13 (a)~(d) are the next Figure 12 Explanatory diagram.

[0050] Figure 14 (a)~(c) are the next Figure 13 Explanatory diagram.

[0051] Figure 15 (a) to (d) are explanatory diagrams of a method for manufacturing a photomask according to one embodiment of the present invention.

[0052] Figure 16 (a)~(d) are the next Figure 15 Explanatory diagram.

[0053] Figure 17 (a)~(d) are Figure 15(c) Supplementary illustration of process 3.

[0054] Figure 18 yes Figure 1 (b) and Figure 16 (d) is a partially enlarged sectional view.

[0055] Figure 19 (a) to (d) are explanatory diagrams of a method for manufacturing a photomask blank according to other embodiments of the present invention.

[0056] Symbol Explanation

[0057] 1: Photomask; 2: Photomask blank; 3: Transparent substrate; 4: Semi-transparent film; 5: Light-shielding film; 6: Intermediate film (etching barrier film); 7: Hole pattern; 7A: Hole in the semi-transparent part; 7B: Hole in the light-shielding part; 8: Resist film; 8a: Part; 9: Residue; 10: Stacked part. Detailed Implementation

[0058] <Structure of Photomasks>

[0059] First, the structure of a photomask according to one embodiment of the present invention will be described.

[0060] like Figure 1 As shown, photomask 1 is a multi-grayscale photomask with three grayscale levels, comprising a transmissive portion (blank area), a semi-transmissive portion (shaded area), and a light-shielding portion (blackened area). The transmissive portion is composed of a transparent substrate 3, the semi-transmissive portion is composed of a semi-transparent film 4, and the light-shielding portion is composed of a light-shielding film 5. That is, the exposed portion of the transparent substrate 3 without the semi-transmissive film 4 and the light-shielding film 5 is the transmissive portion, the portion of the transparent substrate 3 with the semi-transmissive film 4 is the semi-transmissive portion, and the portion of the transparent substrate 3 with the light-shielding film 5 is the light-shielding portion.

[0061] The translucent portion is formed in the form of an island pattern, in which unit elements (islands) of a predetermined shape (rectangular in this embodiment) are arranged two-dimensionally at predetermined intervals. The light-blocking portion is formed to fill the area outside the translucent portion. The translucent 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 arranged two-dimensionally at predetermined intervals and located in the areas of the translucent portion and the light-blocking portion, respectively.

[0062] 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 relative to the representative wavelength (e.g., i-line, h-line, or g-line) contained in the exposure light used in the exposure process using the photomask 1. Furthermore, the exposure light can be, for example, i-line, h-line, or g-line, or it can be a mixture of at least two of these wavelengths. Alternatively, the exposure light can be light whose wavelength band is shifted or extended relative to these wavelengths towards shorter and / or longer wavelengths. As an example, the wavelength band of the exposure light can be light with a bandwidth extended from 365 nm to 436 nm to 300 nm to 450 nm. However, the exposure light is not limited to this.

[0063] The semi-permeable film 4 uses a Cr-based material, such as Cr or Cr-based compounds, Ni or Ni-based compounds, Ti or Ti-based compounds, Si-based compounds, or metal silicide compounds. In this embodiment, the semi-permeable film 4 uses a Cr-based compound. The semi-permeable film 4 is a phase-shifting film. Alternatively, the semi-permeable film 4 can also be a halftone film. The semi-permeable film 4 is configured to have a transmittance of 5% to 70% relative to the representative wavelength contained in the exposure light, which is lower than that of the transparent substrate 3 and higher than that of the light-shielding film 5. In addition, the semi-permeable film 4 can also be a semi-transparent metal film in which the in-plane transmittance distribution of the photomask 1 is improved by adjusting the nitrogen content. Furthermore, by including other elements in the semi-permeable film 4, the optical density (OD value) of the semi-transparent portion can be changed. The semi-permeable film 4 is formed on the transparent substrate 3 by sputtering, evaporation, or the like.

[0064] The light-shielding film 5 uses the same material as the semi-permeable film 4. In this embodiment, the light-shielding film 5 uses a Cr-based compound. The light-shielding film 5 has a transmittance of less than 1% relative to the representative wavelength contained in the exposure light. Alternatively, it is acceptable as long as the optical density (OD value) of the light-shielding portion is 2.7 or higher. As an example, the light-shielding film 5 has a stacked structure having a first film layer and a second film layer. The first film layer is composed of a Cr film for light-shielding purposes. The second film layer is composed of a chromium oxide film for suppressing reflection. In this case, even if the transmittance of the first film layer is higher than 1%, it is acceptable as long as the transmittance of the stacked first and second film layers is less than 1%. The light-shielding film 5 is formed on the transparent substrate 3 by sputtering, vapor deposition, or the like.

[0065] Since the semi-permeable membrane 4 and the light-shielding membrane 5 are made of the same material, they have the same etching characteristics. However, since the semi-permeable membrane 4 and the light-shielding membrane 5 and the intermediate membrane 6 (described later) are made of different materials, they have different etching characteristics. That is, the semi-permeable membrane 4 and the light-shielding membrane 5 have etching selectivity relative to the intermediate membrane 6, and the intermediate membrane 6 has etching selectivity relative to the semi-permeable membrane 4 and the light-shielding membrane 5.

[0066] <Structure of photomask preform>

[0067] Next, the structure of a photomask blank, which serves as the basis for photomask 1, according to one embodiment of the present invention will be described.

[0068] like Figure 2 As shown, the photomask blank 2 is the photomask blank in the state before the aperture pattern 7 of the photomask 1 is formed. That is, the photomask blank 2 is formed in such a way that the semi-permeable film 4 and the light-shielding film 5 are edge-to-edge and arranged in the same plane without any transmissive portion on the entire surface (effective area) of the transparent substrate 3. In addition, although it refers to the same plane, the thickness of the semi-permeable film 4 and the light-shielding film 5 is not necessarily the same. For example, it is possible that the thickness of the semi-permeable film 4 is less than the thickness of the light-shielding film 5, or vice versa.

[0069] <First Manufacturing Method for Photomask Preform>

[0070] Next, the manufacturing method of the photomask blank 2 according to Embodiment 1 of the present invention (the first manufacturing method of photomask blank 2) will be described.

[0071] In general, the manufacturing method is a method for manufacturing a photomask preform 2, wherein the surface of a transparent substrate 3 is divided into a first patterned region and a second patterned region; a first functional film is formed in the first patterned region; and a second functional film is formed in the second patterned region. The first patterned region is the region of a semi-permeable film 4, and the second patterned region is the region of a light-shielding film 5. The first functional film is the semi-permeable film 4, and the second functional film is the light-shielding film 5. Furthermore, a functional film refers to a film that has the function of adjusting the optical properties of the exposure light. Functional films include phase-shifting films that have the function of changing the phase of the exposure light, semi-permeable films that have the function of adjusting the transmittance of the exposure light, and light-shielding films that have the function of blocking the exposure light, etc.

[0072] Specifically, the manufacturing method includes:

[0073] i) Photomask blank preparation process (process 1)

[0074] ii) Resist film formation process (process 2)

[0075] iii) Drawing process (process 3)

[0076] iv) Developing process (process 4)

[0077] v) Intermediate film etching process (process 5)

[0078] vi) Semi-permeable membrane etching process (process 6)

[0079] vii) Resist film removal process (process 7)

[0080] viii) Light-shielding film formation process (process 8)

[0081] ix) Resist film formation process (process 9)

[0082] x) Depicting the process (process 10)

[0083] xi) Developing process (process 11)

[0084] xii) Light-shielding film etching process (process 12)

[0085] xiii) Intermediate film etching process (process 13)

[0086] xiv) Resist film removal process (process 14)

[0087] xv) Finishing process (process 15).

[0088] Furthermore, the process from resist film formation (process 2) to resist film removal (process 7) and from resist film formation (process 9) to resist film removal (process 14) are respectively referred to as patterning processes. In the former patterning process, the semi-permeable film 4 of the photomask blank 2 is patterned, and in the latter patterning process, the light-shielding film 5 of the photomask blank 2 is patterned.

[0089] like Figure 3 As shown in (a), in the photomask preform preparation process (process 1), a semi-permeable film 4 is formed on a transparent substrate 3, and an intermediate film (etch barrier film) 6 is formed on the semi-permeable film 4. Thus, a photomask preform (first photomask preform) is prepared, in which the semi-permeable film 4 and the intermediate film 6 are stacked on the transparent substrate 3. The intermediate film 6 uses a non-Cr-based material. In this embodiment, the intermediate film 6 uses Ni, Ti, or a molybdenum silicide compound. The semi-permeable film 4 and the intermediate film 6 are formed by sputtering, vapor deposition, or other methods.

[0090] like Figure 3 As shown in (b), in the first resist film formation process (process 2), the resist is uniformly coated onto the intermediate film 6 to form the resist film 8. The resist is coated by a coating method or a spraying method.

[0091] like Figure 3 As shown in (c), in the first drawing process (process 3), an electron beam or laser from a drawing apparatus is used to irradiate the resist film 8 with exposure light to draw a resist pattern corresponding to the area of ​​the semi-permeable film 4 of the photomask blank 2. In addition to drawing the resist pattern, in the first drawing process (process 3), marks (alignment marks) are also drawn to align the drawing positions in the second drawing process (process 10). Although not shown, the alignment marks are formed, for example, at three or four appropriate locations surrounding the outer area of ​​the resist pattern.

[0092] like Figure 3As shown in (d), in the first developing step (step 4), the unwanted resist film 8 (part 8a) is removed by developing, forming a resist pattern. Developing is performed by immersion in a developing solution. Furthermore, the drawing step (step 3) and the developing step (step 4) are collectively referred to as the resist patterning step.

[0093] like Figure 4 As shown in (a), in the intermediate film etching process (process 5), a photoresist pattern is used as a mask for etching, and the exposed portion of the intermediate film 6 is removed by etching. Etching can be either dry etching or wet etching, but wet etching is preferred for large-sized photomasks. An etchant, either a liquid etchant or an etching gas, is used. Regardless of the type of etchant, an etchant that is selective for etching the intermediate film 6 (an etchant that does not etch the semi-permeable film 4) is used.

[0094] like Figure 4 As shown in (b), in the semi-permeable film etching process (process 6), the intermediate film 6 is used as an etching mask, and the exposed portion of the semi-permeable film 4 is removed by etching. Etching can be either dry etching or wet etching, but wet etching is preferred for large-sized photomasks. An etchant, either a liquid etchant or an etching gas, is used. Regardless of the type of etchant, an etchant that is selective for etching the semi-permeable film 4 (an etchant that does not etch the intermediate film 6) is used.

[0095] like Figure 4 As shown in (c), in the first resist film removal process (process 7), the resist film 8 is removed. The resist film 8 is removed by ashing or by immersion in a resist stripping solution.

[0096] like Figure 5 As shown in (a), in the light-shielding film formation process (process 8), a light-shielding film 5 is formed on the exposed portion of the transparent substrate 3 after the semi-permeable film 4 has been removed and on the semi-permeable film 4. The light-shielding film 5 is formed by sputtering, vapor deposition, or other methods.

[0097] like Figure 5 As shown in (b), in the second resist film formation step (step 9), the same as in the first resist film formation step (step 2), a resist is applied to the light-shielding film 5 to form a resist film 8. The resist is applied by coating or spraying.

[0098] like Figure 5(c) As shown, in the second drawing process (process 10), similar to the first drawing process (process 3), an electron beam or laser from a drawing apparatus is used to irradiate the resist film 8 with exposure light to draw a resist pattern corresponding to the area of ​​the light-shielding film 5 on the photomask blank 2. The drawing apparatus is the same apparatus used in the first drawing process (process 3). In the second drawing process (process 10), the drawing apparatus detects the alignment marks formed in the first drawing process (process 3) and aligns the transparent substrate 3.

[0099] However, even with improved alignment accuracy, completely eliminating alignment deviations is extremely difficult. Therefore, in the second drawing process (process 10), a resist pattern that takes alignment deviations into account is set. Specifically, by offsetting (+offset) the edge of the light-shielding film 5 of the photomask blank 2 outward, a resist pattern is set that overlaps (laps) the edges of the semi-permeable film 4, the intermediate film 6, and the overlapping portion of the light-shielding film 5 with an overlap amount L. The overlap amount L is, for example, a value of 0.3 μm or more and 0.5 μm or less.

[0100] like Figure 5 As shown in (d), in the second developing step (step 11), the same as in the first developing step (step 4), the unwanted resist film 8 (part 8a) is removed by developing to form a resist pattern. Developing is performed by immersion in a developing solution. Furthermore, the drawing step (step 10) and the developing step (step 11) are collectively referred to as the resist patterning step.

[0101] like Figure 6 As shown in (a), in the photomask etching process (step 12), the resist pattern is used as a mask for etching, and the exposed portion of the photomask 5 is removed by etching. Etching can be either dry etching or wet etching, but wet etching is preferred for large-sized photomasks. An etchant or an etching gas is used. Regardless of the type of etchant, an etchant that is selective for etching the photomask 5 (an etchant that does not etch the intermediate film 6) is used.

[0102] like Figure 6 As shown in (b), in the intermediate film etching process (step 13), a light-shielding film 5 (or a resist pattern if there is no residual light-shielding film 5) is used as the etching mask to remove the exposed portion of the intermediate film 6. Etching can be either dry etching or wet etching, but wet etching is preferred for large-sized photomasks. An etchant, either a liquid etchant or an etchant gas, is used. Regardless of the type of etchant, an etchant that is selective for etching the intermediate film 6 (an etchant that does not etch the semi-permeable film 4) is used.

[0103] like Figure 6As shown in (c), in the second resist film removal process (process 14), the resist film 8 is removed in the same manner as in the first resist film removal process (process 7). The resist film 8 is removed by ashing or by immersion in a resist stripping solution.

[0104] like Figure 6 As shown in (d), in the finishing process (process 15), the residue 9 of the intermediate film 6 and the light-shielding film 5 remaining due to the aforementioned overlap is removed. Since the residue 9 is narrow and has low rigidity, it 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 process (process 12) and the intermediate film 6 is side-etched in the intermediate film etching process (process 13), thus eliminating the residue 9, then the finishing process (process 15) is unnecessary.

[0105] After the above processes 1 to 15, the photomask blank 2, which serves as the second photomask blank, is completed.

[0106] <Second Manufacturing Method for Photomask Preform>

[0107] Next, the manufacturing method of the photomask blank 2 according to Embodiment 2 of the present invention (the second manufacturing method of the photomask blank 2) will be described.

[0108] In general, the manufacturing method is a method for manufacturing photomask blank 2 as follows: the surface of transparent substrate 3 is divided 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 the region of light-shielding film 5, the second pattern region is the region of semi-permeable film 4, the first functional film is light-shielding film 5, and the second functional film is semi-permeable film 4.

[0109] Specifically, the manufacturing method includes:

[0110] i) Photomask blank preparation process (process 1)

[0111] ii) Resist film formation process (process 2)

[0112] iii) Drawing process (process 3)

[0113] iv) Developing process (process 4)

[0114] v) Intermediate film etching process (process 5)

[0115] vi) Light-shielding film etching process (process 6)

[0116] vii) Resist film removal process (process 7)

[0117] viii) Semi-permeable membrane formation process (process 8)

[0118] ix) Resist film formation process (process 9)

[0119] x) Depicting the process (process 10)

[0120] xi) Developing process (process 11)

[0121] xii) Semi-permeable membrane etching process (process 12)

[0122] xiii) Intermediate film etching process (process 13)

[0123] xiv) Resist film removal process (process 14)

[0124] xv) Finishing process (process 15).

[0125] Furthermore, the process from resist film formation (process 2) to resist film removal (process 7) and from resist film formation (process 9) to resist film removal (process 14) are respectively referred to as patterning processes. In the former patterning process, the light-shielding film 5 of the photomask blank 2 is patterned, and in the latter patterning process, the semi-permeable film 4 of the photomask blank 2 is patterned.

[0126] The second manufacturing method differs from the first manufacturing method in that, in the first manufacturing method, the semi-permeable membrane 4 is patterned first, and then the light-shielding membrane 5 is patterned, while in the second manufacturing method, the light-shielding membrane 5 is patterned first, and then the semi-permeable membrane 4 is patterned. Apart from these related matters, the two methods are identical. Therefore, the differences will be explained below, while the similarities will be omitted as they are the same as those explained in the first manufacturing method.

[0127] like Figure 7 As shown in (a), in the photomask preparation process (process 1), a light-shielding film 5 is formed on a transparent substrate 3, and an intermediate film (etching barrier film) 6 is formed on the light-shielding film 5, thereby preparing a photomask blank (first photomask blank) on which the light-shielding film 5 and the intermediate film 6 are stacked on the transparent substrate 3.

[0128] like Figure 7 As shown in (c), in the first drawing process (process 3), a resist pattern corresponding to the area of ​​the light-shielding film 5 of the photomask blank 2 is drawn.

[0129] like Figure 8 As shown in (a), in the intermediate film etching process (process 5), a resist pattern is used as a mask for etching, and the exposed portion of the intermediate film 6 is removed by etching. The etchant used is an etchant that has etching selectivity for the intermediate film 6 (an etchant that does not etch the light-shielding film 5).

[0130] like Figure 8As shown in (b), in the light-shielding film etching process (process 6), the intermediate film 6 is used as a mask for etching, and the exposed portion of the light-shielding film 5 is removed by etching. The etchant used is an etchant that has etching selectivity for the light-shielding film 5 (an etchant that does not etch the intermediate film 6).

[0131] like Figure 9 As shown in (a), in the semi-permeable film forming process (process 8), a semi-permeable film 4 is formed on the exposed portion of the transparent substrate 3 after the light-shielding film 5 has been removed and on the light-shielding film 5.

[0132] like Figure 9 As shown in (c), in the second drawing process (process 10), a resist pattern corresponding to the area of ​​the semi-permeable film 4 of the photomask blank 2 is drawn. However, the resist pattern is a resist pattern that is set by offsetting (+offset) the edge of the semi-permeable film 4 of the photomask blank 2 outward, and overlapping (lap) the edges of the stacked portion of the light-shielding film 5, the intermediate film 6, and the semi-permeable film 4 with an overlap amount L.

[0133] like Figure 10 As shown in (a), in the semi-permeable membrane etching process (process 12), the resist pattern is used as a mask for etching, and the exposed portion of the semi-permeable membrane 4 is removed by etching. The etchant used is an etchant that has etching selectivity for the semi-permeable membrane 4 (an etchant that does not etch the intermediate membrane 6).

[0134] like Figure 10 As shown in (b), in the intermediate film etching process (process 13), a semi-permeable film 4 (or a resist pattern if there is no residual semi-permeable film 4) is used as a mask for etching, and the exposed portion of the intermediate film 6 is removed by etching. An etchant that is selective for etching the intermediate film 6 (an etchant that does not etch the light-shielding film 5) is used.

[0135] <Third Manufacturing Method for Photomask Preforms>

[0136] Next, the manufacturing method of the photomask blank 2 according to Embodiment 3 of the present invention (the third manufacturing method of the photomask blank 2) will be described.

[0137] In general, the manufacturing method is a method for manufacturing a photomask blank 2 as follows: the surface of a transparent substrate 3 is divided 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. The first pattern region is the region of a semi-permeable film 4, and the second pattern region is the region of a light-shielding film 5. The first functional film is the semi-permeable film 4, and the second functional film is the light-shielding film 5.

[0138] Specifically, the manufacturing method includes:

[0139] i) Photomask blank preparation process (process 1)

[0140] ii) Resist film formation process (process 2)

[0141] iii) Drawing process (process 3)

[0142] iv) Developing process (process 4)

[0143] v) Semi-permeable membrane etching process (process 5)

[0144] vi) Resist film removal process (process 6)

[0145] vii) Light-shielding film formation process (process 7)

[0146] viii) Resist film formation process (process 8)

[0147] ix) Depicting the process (process 9)

[0148] x) Development process (process 10)

[0149] xi) Light-shielding film etching process (process 11)

[0150] xii) Resist film removal process (process 12)

[0151] xiii) Finishing process (process 13).

[0152] Furthermore, the process from resist film formation (process 2) to resist film removal (process 6) and from resist film formation (process 8) to resist film removal (process 12) are respectively referred to as patterning processes. In the former patterning process, the semi-permeable film 4 of the photomask blank 2 is patterned, and in the latter patterning process, the light-shielding film 5 of the photomask blank 2 is patterned.

[0153] The third manufacturing method differs from the first manufacturing method in that, in the third manufacturing method, i) a photomask preform with only a semi-permeable film 4 formed on the transparent substrate 3 without an interlayer film 6 is used as the first photomask preform, and correspondingly, the interlayer film etching process (process 5) and the interlayer film etching process (process 13) of the first manufacturing method are absent; ii) either the semi-permeable film 4 or the light-shielding film 5 is made of a Cr-based material, and the other is made of a non-Cr-based material. Therefore, the semi-permeable film 4 and the light-shielding film 5 have different etching characteristics due to their different materials, and correspondingly, different etchants are used. Except for matters related to this, the two are the same. Therefore, regarding the third manufacturing method, as the description is the same as that of the first manufacturing method, the explanation is omitted.

[0154] <Fourth Manufacturing Method for Photomask Preforms>

[0155] Next, the manufacturing method of the photomask blank 2 according to Embodiment 4 of the present invention (the fourth manufacturing method of photomask blank 2) will be described.

[0156] In general, the manufacturing method is a method for manufacturing photomask blank 2 as follows: the surface of transparent substrate 3 is divided 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 the region of light-shielding film 5, the second pattern region is the region of semi-permeable film 4, the first functional film is light-shielding film 5, and the second functional film is semi-permeable film 4.

[0157] Specifically, the manufacturing method includes:

[0158] i) Photomask blank preparation process (process 1)

[0159] ii) Resist film formation process (process 2)

[0160] iii) Drawing process (process 3)

[0161] iv) Developing process (process 4)

[0162] v) Light-shielding film etching process (process 5)

[0163] vi) Resist film removal process (process 6)

[0164] vii) Semi-permeable membrane formation process (process 7)

[0165] viii) Resist film formation process (process 8)

[0166] ix) Depicting the process (process 9)

[0167] x) Development process (process 10)

[0168] xi) Semi-permeable membrane etching process (process 11)

[0169] xii) Resist film removal process (process 12)

[0170] xiii) Finishing process (process 13).

[0171] Furthermore, the process from resist film formation (process 2) to resist film removal (process 6) and from resist film formation (process 8) to resist film removal (process 12) are respectively referred to as patterning processes. In the former patterning process, the light-shielding film 5 of the photomask blank 2 is patterned, and in the latter patterning process, the semi-permeable film 4 of the photomask blank 2 is patterned.

[0172] The fourth manufacturing method differs from the third manufacturing method in that, in the third manufacturing method, the semi-permeable membrane 4 is patterned first, and then the light-shielding membrane 5 is patterned, while in the fourth manufacturing method, the light-shielding membrane 5 is patterned first, and then the semi-permeable membrane 4 is patterned. Except for matters related to this, the two methods are identical. Therefore, regarding the fourth manufacturing method, as the description is the same as that of the first and second manufacturing methods, the explanation is omitted.

[0173] <Methods for Manufacturing Photomasks>

[0174] Next, a method for manufacturing a photomask 1 according to one embodiment of the present invention will be described.

[0175] The manufacturing method includes:

[0176] i) Photomask blank preparation process (process 1)

[0177] ii) Resist film formation process (process 2)

[0178] iii) Drawing process (process 3)

[0179] iv) Developing process (process 4)

[0180] v) Film etching process (process 5)

[0181] vi) Resist film removal process (process 6).

[0182] Furthermore, the process from resist film formation (process 2) to resist film removal (process 7) is referred to as the patterning process. In the patterning process, the transmissive portion of the photomask 1 is patterned.

[0183] like Figure 15 As shown in (a), in the photomask blank preparation process (process 1), a photomask blank 2 (second photomask blank) to be manufactured by any of the above-mentioned photomask blank 2 manufacturing methods is prepared.

[0184] like Figure 15 As shown in (b), in the resist film formation process (process 2), the resist is uniformly coated onto the semi-permeable membrane 4 and the light-shielding membrane 5 to form the resist film 8. The resist is coated by a coating method or a spraying method.

[0185] like Figure 15 As shown in (c), in the drawing process (process 3), the electron beam or laser of the drawing device is used to irradiate the resist film 8 with exposure light to draw the resist pattern corresponding to the area of ​​the transmission part (hole pattern 7) of the photomask 1.

[0186] However, although the semi-permeable film 4 and the light-shielding film 5 have the same etching characteristics, if their etching rates differ, the semi-permeable film 4 and the light-shielding film 5 will have different lateral etching amounts in the film etching process (process 5). As a result, the dimensional accuracy (edge ​​position accuracy of at least one of the semi-permeable portion or the light-shielding portion of the photomask 1 relative to the transmissive portion) of at least one of the holes 7A, ... in the semi-transparent portion region or the holes 7B, ... in the light-shielding portion region of the hole pattern 7 of the photomask 1 deteriorates. Therefore, in the drawing process (process 3), a resist pattern that takes into account the etching rate deviation is set. Specifically, for example, when the etching rate of the semi-permeable film 4 is higher than that of the light-shielding film 5, the resist pattern is set as follows: relative to Figure 17 (a) and Figure 17 (b) shows holes 7A and 7B as their original size and shape, such as Figure 17 As shown in (c), relative to the holes 7A, ... located in the region of the semi-transparent section, the edges are offset inward (-offset); or as... Figure 17 As shown in (d), the edges of the holes 7B, ..., located in the area of ​​the light-shielding part are offset outward (+ offset). Of course, if the etching rates of the semi-permeable film 4 and the light-shielding film 5 are the same or similar, offset processing is not required.

[0187] Alternatively, as another method regarding the etching rate, the semi-permeable film 4 and the light-shielding film 5 can be formed (film-forming) in a manner that makes the etching rates of the semi-permeable film 4 and the light-shielding film 5 the same or approximately the same. This is achieved during the fabrication stage of the photomask preform 2 by changing the composition ratio of the compound in the film thickness direction of the semi-permeable film 4, thereby adjusting the etching rate through compositional gradient. For example, a method can be used to slow down the etching rate by increasing the etching difficulty in the film thickness direction toward the direction in which etching occurs. Alternatively, the opposite adjustment method can also be used.

[0188] like Figure 15 As shown in (d), in the developing process (process 4), the unwanted resist film 8 (part 8a) is removed by developing, forming a resist pattern. Developing is performed by immersion in a developing solution. Furthermore, the drawing process (process 3) and the developing process (process 4) are collectively referred to as the resist patterning process.

[0189] like Figure 16 As shown in (a), in the film etching process (process 5), the resist pattern is used as a mask for etching, and the exposed portions of the semi-permeable film 4 and the light-shielding film 5 are removed by etching. The etching can 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.

[0190] However, when the photomask blank 2 is manufactured using the third and fourth manufacturing methods described above, the etching characteristics of the semi-permeable film 4 and the light-shielding film 5 are different, and the etchants used are different. Therefore, the film etching process (process 5) is divided into... Figure 16 (b) shows the semi-permeable membrane etching process (process 5-1) and Figure 16 (c) shows the etching process for the light-shielding film (process 5-2). The order doesn't matter which step comes first.

[0191] like Figure 16 As shown in (d), in the resist film removal process (process 6), the resist film 8 is removed. The resist film 8 is removed by ashing or by immersion in a resist stripping solution.

[0192] After completing steps 1 to 6 above, photomask 1 is finished.

[0193] <Effects of the Implementation Method>

[0194] According to the various manufacturing methods of the photomask blank 2 described above, a composite photomask blank 2 can be manufactured on a transparent substrate 3 in which a semi-permeable film 4 and a light-shielding film 5 are arranged in a planar manner with their edges connected. That is, a photomask blank 2 having two regions with different optical properties. In this photomask blank 2, there is no substantial stacking of the semi-permeable film 4 and the light-shielding film 5. The edges of the pattern of the photomask 1 are respectively defined on the semi-permeable film 4 and the light-shielding film 5, which are essentially single layers. That is, the pattern of the photomask 1 is patterned on the photomask blank 2, which has a small overall film thickness and a small aspect ratio (the ratio of the size to the height of the pattern). This means that edge roughness is less likely to occur at the edges of the pattern of the photomask 1, and the etching time is shortened. Therefore, it is easier to control the size of the pattern during the manufacturing of the photomask 1, and the dimensional accuracy of the pattern in the photomask 1 can be improved.

[0195] Specifically, such as Figure 18 As shown, the semi-permeable membrane 4 and the light-shielding membrane 5 are essentially single-layered. The apertures 7A, ... of the aperture pattern 7 in the photomask 1 are formed in the region of the semi-permeable membrane 4, and the apertures 7B, ... are formed in the region of the light-shielding membrane 5. Therefore, in the photomask 1, the dimensions SA of each aperture 7A and SB of each aperture 7B are faithfully executed according to the design. Thus, compared to forming the aperture pattern on the laminated portion, the dimensional accuracy of each aperture 7A and 7B can be improved, enabling the construction of a high-precision aperture pattern 7 that faithfully adheres to the design.

[0196] Furthermore, according to the manufacturing method of the photomask 1 described above, the pattern of holes 7A, ... is formed in the semi-permeable film 4 and the pattern of holes 7B, ... is formed in the light-shielding film 5 in a single patterning process, rather than in separate patterning processes. Therefore, alignment deviations are naturally avoided, and the relative positional relationship of each hole 7A, 7B, such as the distance D between adjacent holes 7A, 7B, is faithfully completed in the photomask 1. As a result, the positional accuracy of each hole 7A, 7B can be improved, and in this respect, a high-precision hole pattern 7 that faithfully adheres to the design can be patterned.

[0197] Furthermore, according to the first and second manufacturing methods of the aforementioned photomask preform 2, a Cr-based film is used as the semi-permeable film 4 and the light-shielding film 5. Cr-based materials possess high pressure resistance, chemical resistance, and film strength. Therefore, it is possible to obtain the same cleaning resistance as ordinary photomasks.

[0198] <Other Implementation Methods>

[0199] Furthermore, the present invention is not limited to the above-described embodiments, and various changes can be made without departing from the spirit of the present invention.

[0200] In the first and second manufacturing methods of the photomask preform 2 described above, films with the same etching characteristics are selected as the first functional film and the second functional film (in addition, throughout this specification, the terms "same etching characteristics" and "same film material" include the concept of "approximate"). However, the present invention is not limited thereto. For example, i) as the first functional film, a film with etching characteristics different from the second functional film and the intermediate film can be selected; as the second functional film, a film with etching characteristics different from the first functional film and the intermediate film can be selected. Or, ii) as the first functional film, a film with etching characteristics different from the second functional film and the intermediate film can be selected; as the second functional film, a film with etching characteristics different from the first functional film but the same as the intermediate film can be selected.

[0201] Furthermore, in each of the above-described manufacturing methods of the photomask blank 2, the residue 9 is removed, and the laminated portion completely disappears. However, the present invention is not limited to this. For example, if it is a region in the photomask where the edge of the pattern is irrelevant (does not pass through), then as... Figure 19 As shown, a residual layer 10 may also remain. In this case, the overlap amount L is set to a relatively large value, for example, a value of 1 μm or more and 10 μm or less. Furthermore, Figure 19 This is a diagram corresponding to the first manufacturing method of the aforementioned photomask blank 2.

[0202] Furthermore, as a photomask preform, semi-permeable films with different transmittances can be further formed on the aforementioned photomask preform 2. In this case, the transmittance of the lower semi-permeable film 4 (the first semi-permeable film) is readjusted by the upper semi-permeable film (the second semi-permeable film). That is, the second semi-permeable film serves as a transmittance adjustment film.

[0203] Furthermore, a phase-shifting film can also be formed on the aforementioned photomask preform 2. In this case, the lower semi-permeable film 4 can be set to a degree that does not affect the phase-shifting effect, that is, the phase shift amount can be set to 0 degrees or more and 20 degrees or less.

[0204] Furthermore, in the above embodiment, the pattern of photomask 1 is hole pattern 7. However, hole pattern is merely an example, and the present invention is not limited thereto. The pattern as a photomask may include: a pattern whose edge does not pass through the boundary between the region of the first functional film (first pattern region) and the region of the second functional film (second pattern region) and is set in each region of the first functional film and the region of the second functional film; and a pattern whose edge passes through the boundary between the region of the first functional film and the region of the second functional film and is set across the region of the first functional film and the region of the second functional film. Various patterns may be appropriately adopted.

[0205] Furthermore, in the above embodiments, either the first functional membrane or the second functional membrane is a semi-permeable membrane 4, and the other is a light-shielding membrane 5. However, the present invention is not limited thereto. Suitable functional membranes can be selected from various functional membranes as the first and second functional membranes. For example, a phase-shifting membrane that is not used as a semi-permeable membrane can also be used.

[0206] Furthermore, as long as there is no physical interference, it is of course possible to apply the technical features described above to other embodiments or examples, replace the technical features described above with technical features of other embodiments or examples, or combine the technical features described above with each other. This is the natural intention of the present invention.

Claims

1. A method for manufacturing a photomask preform, comprising dividing the surface of a transparent substrate into a first patterned region and a second patterned region, forming a first functional film in the first patterned region, and forming a second functional film in the second patterned region, characterized in that... include: The photomask preform preparation process involves preparing a first photomask preform on a transparent substrate to form a first functional film. The first patterning process involves patterning the first functional film with a pattern corresponding to the first pattern area, and removing the first functional film from the second pattern area. The functional film forming process involves forming a second functional film on the exposed portion of a transparent substrate from which the first functional film has been removed and on the first functional film. The second patterning process involves patterning the second functional film with a pattern corresponding to the second pattern area, and removing the second functional film from the first pattern area.

2. The method for manufacturing a photomask preform according to claim 1, characterized in that, The second composition process includes: The resist film formation process involves forming a resist film on top of the second functional film; The resist patterning process involves offsetting the edge position of the resist pattern outward to form a resist pattern that overlaps the edges of the stacked portions of the first functional film and the second functional film with a predetermined overlap amount, wherein the resist pattern corresponds to the second pattern area. In the etching process, the resist pattern is used as a mask to remove the exposed portion of the second functional film in the first pattern area by etching.

3. The method for manufacturing a photomask preform according to claim 2, characterized in that, Also includes: The finishing process removes residue from the secondary functional membrane that remains due to the specified amount of overlap.

4. The method for manufacturing a photomask preform according to any one of claims 1 to 3, characterized in that, As a first photomask preform, a photomask preform on which a first functional film is formed on a transparent substrate, and an intermediate film having different etching characteristics from the first functional film is formed on the first functional film. As a second functional film, a film with the same etching properties as the first functional film is used.

5. The method for manufacturing a photomask preform according to claim 4, characterized in that, As the first functional membrane and the second functional membrane, membranes made of materials selected from Cr-based, Ni-based, Ti-based, Si-based, metal silicides, and metals with adjusted nitrogen content are used.

6. The method for manufacturing a photomask preform according to any one of claims 1 to 3, characterized in that, As a first photomask preform, a photomask preform on which a first functional film is formed on a transparent substrate is used; As a second functional film, a film with different etching properties than the first functional film is used.

7. The method for manufacturing a photomask preform according to any one of claims 1 to 3, characterized in that, This manufacturing method is a method for manufacturing a composite photomask blank formed on a transparent substrate in such a way that a first functional film and a second functional film are connected to each other at their edges and arranged in the same plane, wherein the first functional film is a film with the function of adjusting the optical properties of the exposure light. As a second functional film, a film with optical properties that adjust the exposure light is used, and whose function is different from that of the first functional film.

8. The method for manufacturing a photomask preform according to claim 7, characterized in that, As either the first functional membrane or the second functional membrane, a phase-shifting membrane or a halftone membrane is used; A light-blocking film is used as either the first functional film or the second functional film.

9. The method for manufacturing a photomask preform according to any one of claims 1 to 3, characterized in that, Adjust either or both of the first functional film or the second functional film so that their etching rate is the same as that of either the first functional film or the second functional film.

10. A method for manufacturing a photomask, characterized in that, include: The photomask blank preparation process involves preparing a photomask blank to be manufactured by the photomask blank manufacturing method according to any one of claims 1 to 3. The patterning process involves creating patterns for the first functional membrane and the second functional membrane using a prescribed design.

11. The method for manufacturing a photomask according to claim 10, characterized in that, The composition process includes a single drawing process.

12. The method for manufacturing a photomask according to claim 10, characterized in that, The composition process includes: The resist film formation process forms a resist film on the surface of the photomask blank; The resist patterning process forms a resist pattern that takes into account the difference in etching rates between the first functional film and the second functional film, wherein the resist pattern is a resist pattern with a predetermined pattern. In the etching process, the resist pattern is used as a mask to remove the exposed portions of the first functional film and the second functional film by etching.

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