JP7743282B2 - Photomask blank manufacturing method and photomask manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing photomask blanks and a method for manufacturing photomasks.

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 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 passing through this part. A half-tone mask is a photomask that has a half-tone film on part of a transparent substrate and has the function of achieving multiple gradations of three or more by changing the intensity of light passing through this part.

This type of photomask is manufactured through the following steps: i) preparing a photomask blank, which is composed of a transparent substrate and a light-shielding film; ii) forming a resist film on the light-shielding film; iii) drawing a predetermined resist pattern on the resist film and developing away the unnecessary resist film to form the predetermined resist pattern; iv) using the resist pattern as a mask to remove the exposed portions of the light-shielding film by etching; v) removing the remaining resist film; vi) forming a phase shift film or halftone 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 halftone film; viii) drawing a predetermined resist pattern on the resist film and developing away the unnecessary resist film to form the predetermined resist pattern; ix) using the resist pattern as a mask to etch away the exposed portions of the phase shift film or halftone film and the light-shielding film; and x) removing the remaining resist film. For example, Patent Document 1 describes a photomask manufacturing method in which a halftone film is formed as step vi).

Japanese Patent Application Laid-Open No. 2005-257712

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 halftone film. Therefore, when patterning the light-shielding portion, it is necessary to etch both the phase shift film or halftone film and the light-shielding film. However, if the etching rates of the two films are different, the amount of side etching will differ 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 can take longer to etch 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)).

The present invention was made in consideration of these circumstances, and aims to provide a method for manufacturing photomask blanks and a method for manufacturing photomasks that facilitates dimensional control of patterns during photomask manufacturing and improves the dimensional accuracy of patterns in photomasks.

The method for producing a photomask blank according to the first aspect of the present invention comprises 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.
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 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.
This is a method for manufacturing photomask blanks.

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 characteristics different from those of the first functional film is formed on the first functional film,
A structure can be adopted in which a film having the same etching characteristics as the first functional film is used as the second functional film.

in this case,
A configuration can be adopted in which films made of a Cr-based material are used as the first functional film and the second functional film.

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 may have a function of adjusting the optical characteristics of the exposure light, and may have a function different from that of the first functional film.

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 configuration can be adopted in which a light-shielding film is used as the other of the first functional film and the second functional film.

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.

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.

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). 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 for the photomask of Fig. 1. Fig. 2(b) is a cross-sectional view taken along line B-B of Fig. 2(a). 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. 4A to 4C are explanatory diagrams continuing from FIG. 5(a) to 5(d) are explanatory diagrams continuing from FIG. 6(a) to 6(d) are explanatory diagrams continuing from FIG. 7(a) to (d) are explanatory diagrams of a method for manufacturing a photomask blank according to the second embodiment of the present invention. 8(a) to 8(c) are explanatory diagrams continuing from FIG. 9(a) to 9(d) are explanatory diagrams continuing from FIG. 10(a) to 10(d) are explanatory diagrams continuing from FIG. 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. 12(a) and 12(b) are explanatory diagrams continuing from FIG. 11. 13(a) to 13(d) are explanatory diagrams continuing from FIG. 12. 14(a) to 14(c) are explanatory diagrams continuing from FIG. 13. 15(a) to 15(d) are explanatory diagrams of a method for manufacturing a photomask according to one embodiment of the present invention. 16(a) to 16(d) are explanatory diagrams continuing from FIG. 15. 17(a) to 17(d) are supplementary explanatory diagrams for step 3 of FIG. 15(c). FIG. 18 is an enlarged cross-sectional view of a portion of FIG. 1(b) and FIG. 16(d). 19(a) to 19(d) are explanatory diagrams of a method for manufacturing a photomask blank according to another embodiment of the present invention.

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

As shown in Figure 1, photomask 1 is a three-tone multi-tone photomask comprising transparent areas (white areas), semi-transparent areas (hatched areas), and light-shielding areas (black areas). The transparent areas are made up of a transparent substrate 3, the semi-transparent areas are made up of a semi-transparent film 4, and the light-shielding areas are made up of a light-shielding film 5. In other words, the exposed portions of the transparent substrate 3 where the semi-transparent film 4 and light-shielding film 5 are not laminated are the transparent areas, the portions where the semi-transparent film 4 is laminated on the transparent substrate 3 are the semi-transparent areas, and the portions where the light-shielding film 5 is laminated on the transparent substrate 3 are the light-shielding areas.

The semi-transmitting portion is formed in the form of an island pattern in which unit elements (islands) of a predetermined shape (in this embodiment, rectangular) are arranged two-dimensionally at predetermined intervals. The light-shielding portion is formed to fill the area outside 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 (in this embodiment, rectangular) are arranged two-dimensionally at predetermined intervals and are located within both the semi-transmitting portion and the light-shielding portion.

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 the representative wavelengths (e.g., i-line, h-line, or g-line) contained in the exposure light used in the exposure process 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 wavelengths than 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.

The semi-transparent 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-transparent film 4. The semi-transparent film 4 is a phase shift film. Alternatively, the semi-transparent film 4 may be a half-tone film. The semi-transparent film 4 has a transmittance for the representative wavelength contained in the exposure light that is lower than the transmittance of the transparent substrate 3 and higher than the transmittance of the light-shielding film 5, and is set to have a transmittance of 5% to 70% for the representative wavelength. The semi-transparent film 4 may also be a semi-transparent metal film whose transmittance distribution within the surface of the photomask 1 is improved by adjusting the nitrogen content. The semi-transparent film 4 can also contain other elements to change the optical density (OD value) of the semi-transparent portion. The semi-transparent film 4 is formed on the transparent substrate 3 by sputtering, vapor deposition, or other methods.

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 greater. As an example, the light-shielding film 5 has a layered structure including a first film layer and a second film layer. The first film layer is made of a Cr film and is intended to provide light-shielding properties. The second film layer is made of a chromium oxide film and is intended to suppress 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 and second film layers is 1% or less. The light-shielding film 5 is deposited on the transparent substrate 3 by sputtering, vapor deposition, or other methods.

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 than 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.

<Configuration of photomask blanks>
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.

As shown in Figure 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 has no transparent portions on the entire surface (effective area) of the transparent substrate 3, and is formed so that the semi-transparent film 4 and the light-shielding film 5 are aligned on the same plane with their edges in contact with each other. Note that although they are on the same plane, the film thicknesses of the semi-transparent 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-transparent film 4 is smaller than the film thickness of the light-shielding film 5, or vice versa.

<First method for manufacturing 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.

In general, this manufacturing method involves producing 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, the first pattern region being a semi-transparent film 4 region, the second pattern region being a light-shielding film 5 region, the first functional film being the semi-transparent film 4, and the second functional film being the light-shielding film 5. Note that a 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 changes the phase of exposure light, a semi-transparent film that adjusts the transmittance of exposure light, and a light-shielding film that blocks exposure light.

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

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

In the photomask blank preparation process (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 intermediate film 6 are stacked 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 intermediate film 6 are each formed by sputtering, vapor deposition, or the like.

In the first resist film formation process (process 2), as shown in Figure 3(b), resist is uniformly applied onto the intermediate film 6 to form a resist film 8. The resist is applied by coating or spraying.

In the first drawing step (step 3), as shown in Figure 3(c), exposure light is irradiated onto the resist film 8 using an electron beam or laser from a drawing device, and a resist pattern corresponding to the region of the semi-transparent film 4 of the photomask blank 2 is drawn. In addition to drawing the resist pattern, the first drawing step (step 3) also draws marks (alignment marks) for aligning the drawing position in the second drawing step (step 10). Although not shown, alignment marks are formed, for example, in three or four appropriate locations in the outer region surrounding the resist pattern.

In the first development step (step 4), as shown in Figure 3(d), unnecessary resist film 8 (portion 8a) is removed by development, forming a resist pattern. Development is carried out 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.

In the intermediate film etching step (step 5), as shown in Figure 4(a), the exposed portions of the intermediate film 6 are etched away using the resist pattern as an etching mask. Either dry etching or wet etching can be used, but wet etching is preferred for large photomasks. The etchant used is an etching solution or etching gas. Regardless of the etchant used, it must have etching selectivity for the intermediate film 6 (an etchant that does not etch the semi-transparent film 4).

In the semi-transparent film etching step (step 6), as shown in Figure 4(b), the exposed portions of the semi-transparent film 4 are etched away using the intermediate film 6 as an etching mask. While either dry etching or wet etching is acceptable, wet etching is preferred for large photomasks. The etchant used is an etching solution or etching gas. Regardless of the etchant used, it must have etching selectivity for the semi-transparent film 4 (i.e., it does not etch the intermediate film 6).

In the first resist film removal step (step 7), as shown in Figure 4(c), the resist film 8 is removed. The resist film 8 is removed by ashing or by immersion in a resist stripper.

In the light-shielding film formation step (step 8), as shown in Figure 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 top of the semi-transparent film 4. The light-shielding film 5 is formed by a method such as sputtering or vapor deposition.

In the second resist film formation process (process 9), similar to the first resist film formation process (process 2), resist is applied onto the light-shielding film 5 to form a resist film 8, as shown in Figure 5(b). The resist is applied by coating or spraying.

In the second drawing process (step 10), similar to the first drawing process (step 3), as shown in FIG. 5(c), exposure light is irradiated onto the resist film 8 using an electron beam or laser from a drawing device, and a resist pattern corresponding to the area of the light-shielding film 5 on the photomask blanks 2 is drawn. The drawing device is the same device as that used in the first drawing process (step 3). In the second drawing process (step 10), the drawing device detects the alignment marks formed in the first drawing process (step 3) and aligns the transparent substrate 3.

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

In the second development step (step 11), as in the first development step (step 4), the unnecessary resist film 8 (portion 8a) is removed by development, forming a resist pattern, as shown in Figure 5(d). Development is carried out by immersion in a developer. The drawing step (step 10) and development step (step 11) are collectively referred to as the resist pattern formation step.

In the light-shielding film etching step (step 12), as shown in Figure 6(a), the exposed portions of the light-shielding film 5 are etched away using the resist pattern as an etching mask. Either dry etching or wet etching can be used, but wet etching is preferred for large photomasks. The etchant used is an etching solution or etching gas. Regardless of the etchant used, it must have etching selectivity for the light-shielding film 5 (an etchant that does not etch the intermediate film 6).

In the intermediate film etching step (step 13), as shown in Figure 6(b), the exposed portions of the intermediate film 6 are etched away using the light-shielding film 5 (or a resist pattern, if no light-shielding film 5 remains) as an etching mask. Either dry etching or wet etching can be used, but wet etching is preferred for large photomasks. An etchant is an etching solution or etching gas. Either etchant must have etching selectivity for the intermediate film 6 (an etchant that does not etch the semi-transparent film 4).

In the second resist film removal process (step 14), as in the first resist film removal process (step 7), the resist film 8 is removed as shown in Figure 6(c). The resist film 8 is removed by ashing or by immersion in a resist stripper.

In the finishing step (step 15), as shown in Figure 6(d), residues 9 of the intermediate film 6 and light-shielding film 5 remaining after the lapping are removed. Because the residues 9 are narrow and have low rigidity, they can be easily removed by cleaning or other methods. 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.

After going through steps 1 to 15 above, the secondary photomask blank, photomask blank 2, is completed.

<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.

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, the first pattern region being a light-shielding film 5 region, the second pattern region being a semi-transparent film 4 region, the first functional film being the light-shielding film 5, and the second functional film being the semi-transparent film 4.

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

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

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, below, we will only describe the differences, and will omit the same points as those in the first manufacturing method, as they are the same as those in the first manufacturing method.

In the photomask blank preparation process (step 1), as shown in Figure 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 (primary photomask blank) in which the light-shielding film 5 and intermediate film 6 are layered on the transparent substrate 3.

In the first drawing process (step 3), a resist pattern corresponding to the area of the light-shielding film 5 on the photomask blank 2 is drawn, as shown in Figure 7(c).

In the intermediate film etching step (step 5), as shown in Figure 8(a), the exposed portions of the intermediate film 6 are etched away using the resist pattern as an etching mask. An etchant that has etching selectivity for the intermediate film 6 (an etchant that does not etch the light-shielding film 5) is used.

In the light-shielding film etching step (step 6), as shown in Figure 8(b), the exposed portions of the light-shielding film 5 are etched away using the intermediate film 6 as an etching mask. An etchant that has etching selectivity for the light-shielding film 5 (an etchant that does not etch the intermediate film 6) is used.

In the semi-transparent film formation process (step 8), as shown in Figure 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 top of the light-shielding film 5.

In the second drawing process (step 10), as shown in Figure 9(c), a resist pattern corresponding to the region of the semi-transparent film 4 of the photomask blank 2 is drawn. However, the resist pattern is designed to overlap (overlap) the edge of the laminated portion of the light-shielding film 5, intermediate film 6, and semi-transparent film 4 by an overlap amount L, by offsetting (positively offsetting) the edge of the semi-transparent film 4 of the photomask blank 2 outward.

In the semi-transparent film etching step (step 12), as shown in Figure 10(a), the exposed portions of the semi-transparent film 4 are etched away using the resist pattern as an etching mask. An etchant that has etching selectivity for the semi-transparent film 4 (an etchant that does not etch the intermediate film 6) is used.

In the intermediate film etching step (step 13), as shown in Figure 10(b), the exposed portions of the intermediate film 6 are etched away using the semi-transparent film 4 (or a resist pattern, if no semi-transparent film 4 remains) as an etching mask. An etchant that has etching selectivity for the intermediate film 6 (an etchant that does not etch the light-shielding film 5) is used.

<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.

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, the first pattern region being a region of a semi-transparent film 4, the second pattern region being a region of a light-shielding film 5, the first functional film being the semi-transparent film 4, and the second functional film being the light-shielding film 5.

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

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

The third manufacturing method differs from the first manufacturing method in that: i) the third manufacturing method uses a photomask blank as the primary 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, and therefore different etchants. Apart from 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.

<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.

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, the first pattern region being a light-shielding film 5 region, the second pattern region being a semi-transparent film 4 region, the first functional film being the light-shielding film 5, and the second functional film being the semi-transparent film 4.

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

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

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. Apart from this, the two methods are the same. Therefore, the fourth manufacturing method is similar to the descriptions of the first and second manufacturing methods and will not be described further.

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

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

The process from the resist film formation process (step 2) to the resist film removal process (step 7) is called the patterning process. In the patterning process, the transparent portions of the photomask 1 are patterned.

In the photomask blank preparation process (process 1), as shown in Figure 15(a), a photomask blank 2 (secondary photomask blank) manufactured by one of the above-mentioned photomask blank 2 manufacturing methods is prepared.

In the resist film formation process (step 2), as shown in Figure 15(b), 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 coating or spraying.

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 from a drawing device, and a resist pattern corresponding to the transparent portion (hole pattern 7) of the photomask 1 is drawn.

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 will occur between the semi-transparent film 4 and the light-shielding film 5 during the film etching process (Step 5). As a result, the dimensional accuracy (edge position accuracy relative to the transparent portion of at least one of the semi-transparent or light-shielding portions of the photomask 1) of at least one of the holes 7A, located in the semi-transparent region, or the holes 7B, located in the light-shielding region, of the hole pattern 7 of the photomask 1 will be poor. Therefore, in the drawing process (Step 3), a resist pattern is set that takes the difference in etching rate into account. Specifically, if the etching rate of the semi-transparent film 4 is higher than that of the light-shielding film 5, for example, holes 7A and 7B shown in Figures 17(a) and (b) have their original dimensions, but the resist pattern is set so that the edges of holes 7A, etc. located within the semi-transparent region are offset inward (-offset) as shown in Figure 17(c), or the edges of holes 7B, etc. 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, offset processing is not necessary.

Another method for controlling the etching rate is to form (deposit) the semi-transparent film 4 and the light-shielding film 5 so that their etching rates 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 blank 2, and adjusting the etching rate using a composition gradient. For example, one method is to slow down the etching rate by increasing the difficulty of etching in the direction in which etching progresses in the thickness direction. Alternatively, the opposite adjustment method is also possible.

In the development process (process 4), as shown in Figure 15(d), unnecessary resist film 8 (portion 8a) is removed by development, forming a resist pattern. Development is carried out by immersion in a developer. The drawing process (process 3) and development process (process 4) are collectively referred to as the resist pattern formation process.

In the film etching step (step 5), as shown in Figure 16(a), the exposed portions of the semi-transparent film 4 and the light-shielding film 5 are etched away using the resist pattern as an etching mask. While either dry etching or wet etching may be used, wet etching is preferred for large photomasks. An etching solution or etching gas is used as the etchant.

However, in the case of photomask blanks 2 manufactured by the third and fourth manufacturing methods for 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 Figure 16(b) and a light-shielding film etching step (step 5-2) shown in Figure 16(c). The order of these steps does not matter.

In the resist film removal step (step 6), the resist film 8 is removed, as shown in Figure 16(d). The resist film 8 is removed by ashing or by immersion in a resist stripper.

Photomask 1 is completed through steps 1 to 6 above.

<Effects of the embodiment>
According to each of the above-described methods for manufacturing photomask blanks 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, i.e., a photomask blank 2 having two regions with different optical properties. 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. In other words, 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.

Specifically, as shown in FIG. 18, the semi-transparent film 4 and the light-shielding film 5 are each essentially single layers, with holes 7A, etc. of the hole pattern 7 of the photomask 1 being formed in the semi-transparent film 4 region, and holes 7B, etc. being formed in the light-shielding film 5 region. As a result, the dimensions SA of each hole 7A and the dimensions SB of each hole 7B in the photomask 1 are finished faithfully to the design. This improves the dimensional accuracy of each hole 7A, 7B compared to when the hole pattern is formed in the laminated portion, enabling the patterning of a highly accurate hole pattern 7 that is faithful to the design.

Furthermore, according to the manufacturing method of the photomask 1, the patterning of holes 7A, etc. in the semi-transparent film 4 and the patterning of holes 7B, etc. in the light-shielding film 5 are performed in a single patterning process, rather than in separate patterning processes. As a result, alignment 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, on the photomask 1 is finished faithful to the design. This improves the positional accuracy of each hole 7A, 7B, making it possible to pattern a highly accurate hole pattern 7 that is faithful to the design.

Furthermore, according to the first and second manufacturing methods of the photomask blanks 2, films made of Cr-based materials are used for the semi-transparent film 4 and the light-shielding film 5. Cr-based materials are resistant to high pressure and chemicals and have good film strength. This allows for cleaning resistance equivalent to that of general photomasks.

<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.

In the first and second manufacturing methods of the photomask blanks 2, the first and second functional films selected have the same etching characteristics. (Note that throughout this document, when the etching characteristics are "same" and 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 as the intermediate film may be selected.

Furthermore, in each of the manufacturing methods for the photomask blanks 2 described above, 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 areas on the photomask where the edge of the pattern does not overlap (pass through), 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 between 1 μm and 10 μm. Note that FIG. 19 is a drawing corresponding to the first manufacturing method for the photomask blanks 2 described above.

The photomask blank may also be one in which a semi-transparent film with a different transmittance is 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). In other words, the second semi-transparent film functions as a transmittance adjusting film.

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.

Furthermore, in the above embodiment, the pattern of the photomask 1 is a hole pattern 7. However, this is merely an example, and the present invention is not limited to this. The photomask pattern can be of various types, 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 both the first functional film region and the second functional film region.

In addition, 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. Appropriate functional films can be selected from a variety of functional films as the first functional film and the second functional film. For example, they may be phase shift films that are not intended as semi-transparent films.

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.

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 (13)

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 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. The second patterning step includes:
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;
The method for producing a photomask blank according to claim 1 or 2 , further comprising an etching step of removing exposed portions of the second functional film in the region of the first pattern by etching using the resist pattern as a mask. The method for manufacturing a photomask blank according to claim 3 , further comprising a finishing step of removing residue of the second functional film remaining due to the predetermined overlap amount. 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,
5. The method for manufacturing a photomask blank according to claim 1 , wherein the second functional film is a film having the same etching characteristics as the first functional film. 6. The method for manufacturing photomask blanks according to claim 5, wherein the first functional film and the second functional film are made of a material selected from the group consisting of Cr-based, Ni-based, Ti-based, Si-based, metal silicide-based, and metals with adjusted nitrogen content. As the first photomask blank, a photomask blank in which a first functional film is formed on a transparent substrate is used,
The method for manufacturing a photomask blank according to claim 1 , wherein the second functional film has etching characteristics different from those of the first functional film. As the first functional film, a film having a function of adjusting the optical characteristics of exposure light is used,
The method for producing a photomask blank according to any one of claims 1 to 7 , wherein the second functional film is a film having a function of adjusting optical properties of exposure light, which function is different from that of the first functional film. a phase shift film or a halftone 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 , wherein the other of the first functional film and the second functional film is a light-shielding film. 10. The method for producing a photomask blank according to claim 1, wherein either one or both of the first functional film and the second functional film are adjusted so that the etching rate of either the first functional film or the second functional film is the same as that of the other of the first functional film and the second functional film. 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 ;
a patterning step of patterning the first functional film and the second functional film into a predetermined pattern. The method for manufacturing a photomask according to claim 11 , wherein the patterning step comprises a single drawing step. 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;
The method for manufacturing a photomask according to claim 11 or 12 , further comprising 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.