JP2011186506A - Halftone photomask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly precise halftone photomask with little pattern deviation. <P>SOLUTION: A device pattern part on a transparent substrate 1 includes: a light-shielding part where a semi-transmissive film 5 having relatively very low reflectance and high transmittance is laminated on a light-shielding film 4 having relatively high reflectance and very low transmittance; a semi-transmissive part where the semi-transmissive film 5 is directly deposited on the transparent substrate; and a light-transmissive part 7 where a part of the light-shielding part or the semi-transmissive part is removed to expose the transparent substrate. Meanwhile, an alignment mark 2 is provided in an alignment mark part provided in a non-device-pattern part on the transparent substrate 1, by: the light-transmissive part where neither the light-shielding film nor the semi-transmissive film exist and the transparent substrate is exposed; and the light-shielding part where the light-shielding film on the surface of which an antireflective film is not formed is exposed to the outermost surface. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a halftone photomask applied to a flat panel display or the like.

  A conventional photomask (this is referred to as “two-tone photomask” in this specification) has a light transmitting portion (hereinafter referred to as “light transmitting portion”) and a light shielding portion on the surface of a transparent substrate. A tone pattern is provided, which is used to form a desired pattern. Usually, a photomask uses a plurality of two-tone photomasks of various patterns, and a plurality of exposures are performed several times to finally form one pattern. Of course, the pattern has two tones (that is, black and white). (Binary).

  In a technical field such as a semiconductor photomask, a photomask in which a translucent film having a predetermined pattern called a “phase shifter” is formed on the surface of a transparent substrate (referred to as a “halftone phase shift mask” in this specification). .) Is used to improve the resolution. However, the purpose of providing the phase shifter is merely to reproduce the design data. In this case, the transferred pattern has two gradations.

  On the other hand, in a technical field such as a flat panel display, a pattern having a gray-tone gradation is transferred by limiting the exposure amount not by using a halftone mask as a “phase shifter” but by a film transmittance. Thus, a three-tone photomask is obtained. Note that such a photomask is referred to as a “halftone photomask (gray tone mask)” in this specification.

  In this way, when a pattern is formed using a halftone mask and the exposure amount is limited by the transmittance of the film, patterning with different exposure amounts can be performed by one exposure, resulting in a reduction in the exposure process as a result. Can do.

  Here, an example of a conventional halftone photomask (here, a representative “three-tone” photomask) will be described. A conventional general halftone photomask is formed from a pattern in which the first layer is formed by a light-shielding film (light-shielding pattern), and a pattern in which the second layer is formed by a semi-transmissive film (half-tone pattern). It is composed of three gradations of a part, a light shielding part, and a light transmitting part.

  For example, according to Patent Document 2, in a device pattern portion (device forming region) in one photomask, a layer (A) having only a semi-transmissive film, a light-shielding film, and a layer having a semi-transmissive film formed thereon (B) ), A state where three gradations of the layer (C) in which neither the semi-transmissive film nor the light-shielding film is formed is formed (see, for example, FIG. 1 (9)).

  In the halftone photomask manufacturing method, patterning is generally performed at least twice (etching of the light shielding film and etching of the semi-transmissive film). Specifically, the exposure area is divided into an area for forming an alignment mark (alignment pattern portion) and an area for forming a device pattern (device pattern portion) in advance, and the alignment mark is formed during the first pattern formation. In the second patterning, the alignment is performed using this alignment mark.

  FIG. 8A shows a mask (hereinafter referred to as “mask blanks”) in which a light-shielding film 101 is uniformly formed on a transparent substrate 100. Mask blanks are often used when a conventional general two-tone photomask is formed. FIG. 8B schematically shows a state of an exposure process using a conventional two-tone photomask obtained by forming a resist film on the surface of the mask blank 100 shown in FIG. Represents.

  By the way, as shown in FIG. 8 (a), the conventional general mask blanks are not simply the light shielding film 101 covering the entire surface of the transparent substrate, but strictly speaking, a thin low reflectance film ( An antireflection film 102 is formed (this is referred to as “antireflection processing”).

  The reason is assumed that there is a photomask (for example, as shown in FIG. 8C) formed using a mask blank in which the low reflectance film 102 is not formed. FIG. 8C schematically shows an exposure process using a conventional two-tone photomask formed using a virtual mask blank in which the low reflectance film 102 is not formed on the surface. . As shown in this figure, since the surface of the light shielding film 101 generally has a very high reflectance, the light reflected from the exposure target 104 when the exposure light 103 is incident from the back side of the completed photomask is photomask. With this light-shielding pattern, it is reflected again to the exposure target side, and normal exposure cannot be performed. Therefore, all current mask blanks have anti-reflection processing on the surface (for example, Patent Document 1).

  The low reflectance film 102 is often omitted if not particularly required, but for the reasons described above, the low reflectance film 102 is always provided on the outermost surface of the mask blank. In other words, it can be said that a mask blank that is not subjected to antireflection processing on the outermost surface is an extremely abnormal mask blank that is hardly considered in the recent technical level in the technical field to which the present invention belongs.

  In the case of forming a halftone photomask, as in the case of forming a two-tone photomask, it is generally manufactured from a mask blank having a configuration as shown in FIG. In that case, after patterning the light-shielding film as the first layer, a second layer (semi-transmissive film) covering the first layer is formed, and patterning is performed again.

  The drawing process for the second layer includes an alignment mark provided in a non-device region (referred to herein as “alignment mark portion (I)”) at the periphery of the substrate when the light-shielding pattern for the first layer is formed. The laser beam is irradiated and the reflected light (this is called “alignment signal”) is read to perform alignment. However, since the reflectivity of the second layer (semi-transmissive film) is usually very low, if the second layer (semi-transmissive film) remains in the alignment mark portion, the reflectivity is remarkably lowered, and the alignment signal is reduced. The problem that it cannot be read may arise.

FIG. 9A shows the incident intensity I ₁ and reflection intensity I ₂ of the alignment signal when the second-layer semi-transmissive film 105 is formed on the outermost surface of the alignment mark portion (I). This figure shows that the incident light intensity I ₁ with respect to the alignment mark portion is attenuated by the semi-transmissive film 105 and the reflected light intensity I ₂ is remarkably reduced.

  As described above, as a method for solving the technical problem that the read signal of the optical alignment mark is lowered due to the extremely low reflectance of the “semi-transmissive film 102”, A method is known in which a semi-permeable membrane is not formed on the top (see Patent Documents 2 to 4, etc.).

  FIG. 9B shows the mask blanks shown in FIG. 8A as a starting material, as shown in Patent Document 2, for example, on the light shielding film in the alignment mark portion using a shielding plate during film formation of the second layer. It is a figure which shows the photomask comprised so that a semi-permeable film may not be formed in FIG. According to this method, since the semi-transmissive film 103a is not formed in the alignment mark portion, a decrease in the alignment signal can be suppressed to some extent.

JP 05-127362 A JP 2006-227365 A JP 2000-98583 A JP 7-319148 A

However, as shown in FIG. 9B, even if it is configured so that the second-layer semi-transmissive film is not formed in the alignment mark portion, it is originally present on the light-shielding film as long as the conventional mask blanks are used. It is inevitable that the reflected light intensity I ₃ is attenuated by the low reflectance film (antireflection film) 102 that should be attenuated rather than the incident light intensity I _{1 with} respect to the alignment mark portion.

  Thus, as long as a conventional mask blank having an antireflection film on the outermost surface of the light shielding film is used, the alignment mark can be formed so that no semi-transmissive film is formed on the light shielding film in the alignment mark portion. If even a slight low-reflectance film was exposed on the outermost surface of the part, the alignment mark signal was attenuated and an alignment error was likely to occur.

  For example, according to the method described in Patent Document 2, since the translucent film does not exist on the light transmitting part in the mark pattern part, the attenuation of the alignment signal is suppressed to a certain degree. However, the substantial meaning of “constitute so that no semi-permeable membrane exists” described in the same document means that the second-layer semi-permeable membrane is not formed in the alignment mark portion. It does not mean that the high reflectivity film is exposed. In other words, it is not necessarily a necessary and sufficient means for the technical problem of preventing attenuation of the alignment signal.

  Further, in Patent Document 3, since the semi-transmissive film is used as a phase shifter, the semi-transmissive film is not finally exposed on the entire surface of the substrate, and therefore, mask blanks subjected to antireflection processing are used. It is assumed that. Since a mask blank provided with a low reflectivity film is used as a starting material and a step of selectively removing the low reflectivity film in the alignment mark portion is required, it is wasteful. In this sense, even if the photomask uses the same semi-transmissive film, “phase shift mask” and “halftone photomask” require completely different considerations.

  The present invention has been made in view of the above, and has as its main technical problem to provide a high-precision halftone photomask with extremely small pattern deviation.

  The halftone photomask according to the present invention transmits a device layer (II) on the transparent substrate 1 having a relatively low reflectance and a relatively low transmittance on the light shielding film 4 having a relatively high reflectance and a very low transmittance. The light-shielding portion where the high-permeability semi-transmissive film 5 is laminated, the semi-transmissive portion where the semi-transmissive film 5 is directly deposited on the transparent substrate, and the light-shielding portion or a part of the semi-transmissive portion are removed On the other hand, the light-shielding film and the semi-transmissive film are not present in the alignment mark part (I) provided in the non-device pattern part on the transparent substrate 1. The alignment mark 2 is formed by the light-transmitting part where the transparent substrate is exposed and the light-shielding part where the anti-reflection film is not formed on the surface and the light-shielding part where the light-shielding film is exposed on the outermost surface.

  According to such a configuration, since the attenuation of the alignment signal can be suppressed at the time of manufacture, the alignment signal can be reliably read, and as a result, the deviation between the light shielding film pattern and the semi-transmissive film pattern can be reduced.

  The device pattern obtained by using this halftone photomask is a pattern in which the first device pattern formed by the light-shielding film is overlaid with the second device pattern formed by the semi-transmissive film, and at least the semi-transmissive portion And a three-tone pattern of a light shielding portion and a light transmitting portion. In addition, since the semi-transmissive film having a relatively low reflectance is exposed on most of the outermost surface of the device pattern portion, the semi-transmissive film also functions as an antireflection film.

  In the halftone photomask according to the present invention, the semi-transmissive part may be composed of two or more semi-transmissive films made of the same material and partially different in film thickness. In this way, a halftone photomask having four or more gradations can be realized.

  According to the halftone photomask according to the present invention, it is possible to realize a highly accurate halftone photomask with extremely small pattern deviation. By using this halftone photomask, the conventional photolithography process using multiple photomasks can be done in one step, which simplifies the manufacturing process and reduces costs. The Furthermore, if the configuration includes two or more semi-transmissive films having different transmittances, the number of gradations of three gradations or more can be realized.

FIG. 1A is a plan view of a photomask in a state where patterning of the first layer (light-shielding film) is completed in the halftone photomask manufacturing process according to the first embodiment of the present invention. . FIG. 1B shows a cross-sectional view taken along line X1-X1 in FIG. FIG.1 (c) has shown the Y1-Y1 sectional view taken on the line in FIG.1 (c) in Fig.1 (a). FIG. 2A shows the substrate surface of the photomask in a state immediately after the semi-transmissive film 5 as the second layer is formed following the state of FIG. FIG. 2B shows a cross-sectional view taken along line X2-X2 in FIG. FIG. 2C shows a cross-sectional view taken along line Y2-Y2 in FIG. 3A is a plan view of the completed three-tone halftone photomask 10 according to the first embodiment of the present invention, and FIG. 3B is a cross-sectional view taken along line X3-X3 in FIG. The figure is shown. Moreover, FIG.3 (c) has shown the Y3-Y3 sectional view taken on the line in Fig.3 (a). FIG. 4A shows a jig 20 for shielding the alignment mark portion (I) for manufacturing the three-tone halftone photomask 10 according to the first embodiment of the present invention. FIG. 4B shows the second layer pattern data 21 converted into the optimum data. FIG. 5A to FIG. 5C are views for explaining a halftone photomask according to the second embodiment. FIG. 5A is a plan view of a four-tone halftone photomask 30 according to the second embodiment, and FIG. 5B is a cross-sectional view taken along line X4-X4 in FIG. . Moreover, FIG.5 (c) has shown the Y4-Y4 sectional view taken on the line in Fig.5 (a). 6A shows a jig 40a that shields the alignment mark portion (I) and the upper half of the substrate surface, and FIG. 6B shows a jig that shields the alignment mark portion (I) and the lower half of the substrate surface. The tool 40b is shown. FIG. 7A shows an example of alignment marks applicable to the halftone photomask manufacturing method according to the first and second embodiments of the present invention. FIG. 7B schematically shows an oscilloscope signal waveform representing an alignment signal when the alignment mark in FIG. 7A is irradiated with laser light. FIG. 8A shows a mask (referred to as “mask blanks”) in which a light shielding film 101 is formed on a transparent substrate 100. FIG. 8B schematically shows a state of an exposure process using a conventional two-tone photomask obtained by forming a resist film on the surface of the mask blank 100 shown in FIG. Represents. FIG. 8C schematically shows a state of an exposure process using a conventional two-tone photomask formed using a mask blank in which the low reflectance film 102 is not formed on the surface. FIG. 9A shows the incident intensity I ₁ and reflection intensity I ₂ of the alignment signal when the second-layer semi-transmissive film 105 is formed on the outermost surface of the alignment mark portion (I). In FIG. 9B, using the mask blank shown in FIG. 8A as a starting material, a semi-transmissive film is not formed on the light shielding film in the alignment mark portion by using a shielding plate when the second layer is formed. It is a figure which shows the comprised photomask.

  Hereinafter, embodiments of a method for producing a halftone photomask according to the present invention will be described in detail with reference to the drawings.

(First embodiment)
First, a special mask blank is prepared in which a light shielding film having a relatively high reflectance and a very low transmittance is exposed on the outermost surface of the transparent substrate. As described above, the mask blank generally has an antireflection film formed on the surface (see FIG. 8A), but in the present invention, the antireflection coating is not applied in this way (not shown). In FIG. 8A, it is necessary to use a mask blank in which the low reflectance film (antireflection film) 102 is not formed.

  Next, a resist is applied to the mask blanks, an alignment mark pattern is formed on the periphery of the substrate by a laser drawing apparatus, and a first device pattern is formed on the other portions, followed by a development and etching process (usually Although it is wet etching, it is not particularly limited.) After the resist removal step and the like, the patterning of the light shielding film as the first layer is completed. Since the alignment mark pattern and the first device pattern are patterned in a single process with respect to the light shielding film, both are referred to as a first resist pattern.

  FIG. 1A is a plan view of a photomask in a state where patterning of the first layer (light-shielding film) is completed in the halftone photomask manufacturing process according to the first embodiment of the present invention. . As shown in this figure, alignment marks 2 (2a to 2d) are formed at four corners of a quartz transparent substrate 1, and a necessary device pattern 3 is formed inside thereof. The shape of the alignment mark is not limited to the shape shown in this figure. As will be described later, a shape in which four straight lines intersect at one point may be used (see FIG. 7A).

  By the way, the device pattern 3 is formed in a “device region” located in the central portion of the substrate 1, whereas the alignment mark is formed in a non-device region located in the peripheral portion of the substrate 1. Therefore, the region where the alignment mark is formed is called “alignment mark portion (I)”, and the region where the device pattern is formed is called “device pattern portion (II)” to be distinguished.

  FIG. 1B shows a cross-sectional view taken along line X1-X1 in FIG. As shown in this figure, a first device pattern is formed by a light shielding film 4 on the surface of the transparent substrate 1 in the device pattern portion (II). FIG.1 (c) has shown the Y1-Y1 sectional view taken on the line in Fig.1 (a). As shown in this figure, an alignment mark 2 is formed on the surface of the transparent substrate 1 in the alignment mark part (I) by a light-transmitting part in which a light-shielding film is not formed and a light-shielding part by the light-shielding film.

  FIG. 2A shows the substrate surface of the photomask in a state immediately after the semi-transmissive film 5 as the second layer is formed following the state of FIG. By forming a film using a jig 20 for shielding the alignment mark portion (I) as shown in FIG. 4A, the entire device pattern portion (II) excluding the alignment mark portion (I) is half-finished. A permeable membrane is formed. The semi-transmissive film as the second layer has a relatively low reflectance relative to the light-shielding film and has a predetermined transmittance defined by the film thickness and the like.

The relationship between the transmissivity of the semi-permeable membrane and the film thickness is as follows: the transmissivity at the unit film thickness L ₀ is T ₀ , the density at the transmissivity T ₀ is D ₀ , and the density at the film thickness L is D Is defined as follows.

D ₀ = −log T ₀ (1)
D = (L / L ₀ ) · D ₀ (2)

  The number of gradations can be further increased by controlling the film thickness according to this equation.

  Note that the jig 20 for shielding the alignment mark portion (I) when forming the semi-permeable film 5 has a moderate inside of the jig in order to prevent the laminated semi-permeable film from being electrostatically damaged. It is better to have roundness.

  FIG. 2B shows a cross-sectional view taken along line X2-X2 in FIG. As shown in this figure, a second device pattern 6 is formed by a semi-transmissive film on the surface of the transparent substrate 1 in the device pattern portion (II).

  Moreover, FIG.2 (c) has shown the Y2-Y2 sectional view taken on the line in Fig.2 (a). As shown in this figure, the alignment mark portion (I) is not formed with a semi-transmissive film on the surface of the transparent substrate 1, and the alignment mark is formed by the light-transmitting portion where the light-shielding film is not formed and the light-shielding portion made of the light-shielding film. 5 is formed.

  Next, after applying a resist on the second-layer semi-transmissive film, a second-layer pattern is formed using a laser drawing apparatus. In order to reduce the alignment error (displacement between the first layer pattern and the second layer pattern), it is necessary to accurately recognize the position of the alignment mark 2 when forming the second layer pattern with the laser drawing apparatus. . In this regard, in the state of FIG. 2A, the alignment mark 2 is not laminated with a semi-transmissive film, and a light-shielding film having a high reflectance is exposed on the outermost surface. Therefore, even if a resist is applied at the time of alignment thereafter, the alignment signal can be sufficiently detected. As a result, the parameter for the arrangement information of the pattern of the second layer is determined. Based on this information, the laser drawing apparatus corrects the drawing start position, expansion / contraction, rotation, and the like of the pattern of the second layer and converts it into optimum data for drawing.

  FIG. 4B shows the second layer pattern data 21 converted into the optimum data. Since this pattern exists in the same coordinate system as the pattern data of the first layer shown in FIG. 1A, the patterns can be superimposed with extremely high accuracy. The second layer pattern data 21 does not require an alignment mark.

  The pattern data 21 of the second layer forms a pattern in which the final finish desires the translucent portion 7. Therefore, when pattern formation is performed by superimposing the second layer pattern 21 on the first layer pattern, finally, a three-tone halftone photomask of a light shielding portion, a light transmitting portion, and a semi-transmissive portion is formed. 10 is completed.

  3A is a plan view of the completed three-tone halftone photomask 10 according to the first embodiment of the present invention, and FIG. 3B is a cross-sectional view taken along line X3-X3 in FIG. The figure is shown. Moreover, FIG.3 (c) has shown the Y3-Y3 sectional view taken on the line in Fig.3 (a).

  As is clear from these drawings, the second etching step etches the second-layer semi-transmissive film and the first-layer light-shielding film all together (normally wet etching, but is not particularly limited). Therefore, the translucent part 7 is formed in both the part of the second device pattern 6 formed of the semi-transmissive film and the part where the light shielding film and the semi-transmissive film are laminated.

(Second Embodiment)
The halftone photomask described in the first embodiment is a three-tone halftone photomask composed of a light-shielding portion, a light-transmitting portion, and a semi-transmissive portion. The halftone photomask can be manufactured.

  FIG. 5A to FIG. 5C are views for explaining a halftone photomask according to the second embodiment. FIG. 5A is a plan view of a four-tone halftone photomask 30 according to the second embodiment, and FIG. 5B is a cross-sectional view taken along line X4-X4 in FIG. . Moreover, FIG.5 (c) has shown the Y4-Y4 sectional view taken on the line in Fig.5 (a). Hereinafter, the manufacturing method will be described.

  First, as in the first embodiment, for example, a first layer pattern as shown in FIG. 1A is formed. Next, when forming the semi-permeable film as the second layer, using the alignment mark (I) as shown in FIG. 6A and the jig 40a for shielding the upper half of the substrate surface, A semi-permeable membrane is laminated.

  Next, using an alignment mark (I) as shown in FIG. 6B and a jig 40b that shields the lower half of the substrate surface, a semi-transparent film having a thickness different from that of the previously laminated semi-transmissive film is used. A permeable membrane is laminated. After that, if the second layer pattern 21 is formed following the example described in the first embodiment, an intermediate having two types of transmissivity with different transmissivities of the semi-transmissive portions on one photomask. The toned photomask 30 is completed.

  This halftone photomask 30 is a three-tone halftone photomask of a light-shielding portion, a light-transmitting portion, and a semi-transmissive portion, and the semi-transmissive portion has two different transmittances. A mask is obtained. If this concept is applied, a multi-tone photomask having 5 gradations or more can be theoretically realized. In particular, a large photomask is highly feasible.

  The first antireflection film is exemplified by a chromium film, and the second semi-transmissive film is exemplified by a chromium oxide film. The relative relationship between reflectance and transmittance is a technical idea of the present invention. As long as it is included in the above, it is not particularly limited.

(About alignment marks)
Each of the halftone photomasks according to the first and second embodiments has a feature that the intensity of the alignment signal is extremely high because the low reflectance film does not exist on the alignment mark. Hereinafter, an example of an actual alignment mark and an alignment signal will be described with reference to FIG.

  FIG. 7A shows an example of alignment marks applicable to the halftone photomask manufacturing method according to the first and second embodiments of the present invention. This alignment mark 50 is drawn by an extremely fine light shielding film in an arbitrary area on the transparent substrate so that the lines of the four light shielding films intersect at one point. The coordinate O of the center position where all the lines intersect is obtained as follows.

  When the intensity of the reflected light at the intersections 51a, 51b, 51c with the light shielding film is measured by scanning the laser light as indicated by the arrows shown in FIG. 7A, three peaks appear. The intensity of the reflected light is detected by a measuring instrument such as an oscilloscope. FIG. 7B schematically shows an oscilloscope signal waveform representing the alignment signal 52 when the alignment mark in FIG. 7A is irradiated with laser light. The operating position of the laser beam is moved as indicated by the dotted line arrows, one side of the upper and lower peaks (corresponding to both ends of the three peaks in FIG. 7B) is detected, and the center coordinates in the X direction are calculated.

  Actually, the laser scanning direction and the Y direction of the mark may not be strictly parallel. In this case, the calculation method of the center coordinates is somewhat complicated, but in any case, it is obtained by the manufacturing method according to the present invention. Since the halftone photomask is composed of a light-shielding film having a high reflectance on the outermost surface of the alignment mark, the alignment signal can be accurately detected. Incidentally, a waveform 53 indicated by a broken line in FIG. 7B is an example of a waveform when the semi-transmissive film remains on the light shielding film, and indicates that three peaks cannot be detected clearly. . In addition, no peak could be detected in the same manner even when the semi-transmissive film did not remain or when the low reflectance film (antireflection film) remained on the surface of the mask blank as the starting material.

  The present invention provides a high-precision halftone photomask in which the shift between the patterns of the first layer and the second layer is extremely small. As a technique that can reduce the number of photolithography processes, the industry is provided. The above applicability is enormous.

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 (2a thru | or 2d) Alignment mark 3 Device pattern 4 Light-shielding film 5 Semi-transmissive film 6 2nd device pattern 7 Translucent part 10 Three-tone halftone photomask 20 Shielding the alignment mark part (I) Jig 21 for the second layer pattern data 30 half-tone photomask 40a jig for shielding the alignment mark portion (I) and the upper half of the substrate surface 40b for the alignment mark portion (I) and the substrate surface Jigs for shielding the lower half 51a to 51c Intersection with the light shielding film 52 Alignment signal I Alignment mark part II Device pattern part

Claims (5)

A light shielding portion in which a semi-transmissive film having a relatively low reflectance and a high transmittance is laminated on a light shielding film having a relatively high reflectance and a very low transmittance on the device pattern portion on the transparent substrate;
A semi-transmissive portion in which the semi-transmissive film is directly deposited on the transparent substrate;
While comprising a light-transmitting part in which a part of the light-shielding part or the semi-transmissive part is removed and the transparent substrate is exposed,
In the alignment mark part provided in the non-device pattern part on the transparent substrate, neither the light-shielding film nor the semi-transmissive film exists, and an antireflection film is formed on the surface of the transparent part and the surface where the transparent substrate is exposed. A halftone photomask, wherein an alignment mark is formed by a light shielding part having the light shielding film exposed on the outermost surface. 2. The halftone photomask according to claim 1, wherein the semi-transmissive portion is composed of two or more semi-transmissive films made of the same material and partially different in film thickness. It is a halftone photomask that has a mark pattern part and a device pattern part manufactured using mask blanks with no low-reflectance film formed on the surface, and a semi-transmissive film is formed on the surface of the device pattern part. 2. The halftone photomask according to claim 1, wherein the semi-transmissive film also functions as a low reflectance film having an antireflection function. 2. The halftone photomask according to claim 1, wherein the graphic pattern of the alignment mark has a shape including a central coordinate O where a plurality of straight lines intersect at one point. 2. The mask blank for manufacturing a halftone photomask according to claim 1, wherein a light shielding film is formed on the entire surface of a flat transparent substrate, and the light shielding film is exposed on the outermost surface.

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