JP7489821B2 - Photomask manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a photomask.

Photomasks are used in the process of manufacturing electronic devices such as flat panel displays. Traditionally, binary masks with transmissive and light-shielding areas have been used as photomasks. However, in recent years, for example, phase-shift masks equipped with a light-shielding film and a phase-shift film have been used to form fine patterns, and multi-tone photomasks have been used to reduce the number of manufacturing steps for electronic devices. Such photomasks have multiple patterns with different optical properties on a transparent substrate, and multiple pattern drawing (exposure) steps are required to form these patterns.

JP 2013-134435 A JP 2017-76146 A

When forming semi-transmitting and light-shielding regions with different optical properties, a photoresist exposure (drawing) process is required for each pattern formation, increasing the number of manufacturing steps. Furthermore, since the photomask substrate is set in an exposure (drawing) device and exposed each time a pattern is drawn, overlay errors (or alignment deviations) may occur. This requires pattern placement that takes the overlay margin into account, making it impossible to obtain fine patterns.

Patent Document 1 discloses a method for forming a pattern made of different materials. Patent Document 1 discloses a method for forming a resist pattern on a laminate of an underlayer film and an upper layer film made of different materials, selectively wet etching the upper layer film and the underlayer film using the resist pattern as a mask, and then side etching the upper layer film using the resist pattern as a mask. Patent Document 1 uses a resist pattern formed in a single drawing process, and can prevent the occurrence of overlay errors, but is unstable because it uses an unnecessary amount of light during exposure, and the pattern size is naturally limited.

Patent Document 2 discloses a method in which a first etching is performed using a first resist pattern formed by preliminary development as a mask, and then additional development is performed to set back the edges of the first resist pattern, followed by a second etching, to form a phase shift film symmetrically on both sides of the light-shielding portion. The manufacturing method disclosed in Patent Document 2 can also prevent overlay errors from occurring in the exposure device, but the patterns that can be formed are limited.

In view of the above problems, the present invention aims to provide a method for manufacturing a photomask that can form patterns having different optical characteristics while suppressing the occurrence of overlay errors during exposure.

The first method for producing a photomask according to the present invention includes the steps of:
preparing a photomask blank having an underlayer film on a transparent substrate and an upper layer film on the underlayer film;
forming a resist film on the upper layer film;
an exposure step of exposing the resist film to light to form a first region, a second region , a third region , and a fourth region having different exposure amounts, and configuring the third region so as to have the second region symmetrically on both sides thereof;
a first resist removal step of selectively removing the first region;
a first etching step of etching the upper layer film and the lower layer film;
a second resist removal step of selectively removing the second region;
a second etching step of etching the upper layer film to form a laminated pattern of the upper layer film and the lower layer film, and forming a rim portion consisting of only the lower layer film in the laminated pattern ;
removing the third region;
The underlayer film has a transmittance of 3 to 15% and a phase shift of approximately 180° .
The laminated pattern has a light-shielding property.
It is characterized by:
A second method for producing a photomask according to the present invention includes the steps of:
preparing a photomask blank having an underlayer film on a transparent substrate and an upper layer film on the underlayer film;
forming a resist film on the upper layer film;
an exposure step of exposing the resist film to light and scanning the resist film with a laser to form a first region, a second region, and a third region having different exposure doses;
a first resist removal step of selectively removing the first region with a developer ;
a first etching step of etching the upper layer film and the lower layer film;
a second resist removal step of selectively removing the second region with a developer ;
a second etching step of etching the upper layer film;
and removing the third region.
A third method for producing a photomask according to the present invention includes the steps of:
preparing a photomask blank having an underlayer film on a transparent substrate and an upper layer film on the underlayer film;
forming a resist film on the upper layer film;
an exposure step of exposing the resist film to light to form a first region, a second region, a third region, and a fourth region having different exposure doses;
a first resist removal step of selectively removing the first region;
a first etching step of etching the upper film and the lower film using the second region, the third region, and the fourth region as a mask;
a second resist removal step of selectively removing the second region;
a second etching step of etching the upper layer film using the third region and the fourth region as a mask, and further etching the lower layer film partially to reduce the film thickness;
a third resist removal step of removing the third region;
a third etching step of etching the upper layer film using the fourth region as a mask;
a fourth resist removal step of removing the fourth region;
The present invention is characterized by comprising:

Further, a method for producing a photomask according to the present invention includes the steps of:
The lower layer and the upper layer are made of different materials.

Further, a method for producing a photomask according to the present invention includes the steps of:
In the exposure step, the exposure amount of the first region is greater than the exposure amount of the second region, and the exposure amount of the third region is zero.

By using this method for manufacturing a photomask, it is possible to form a pattern made of a lower layer film and a pattern made of a lower layer film and an upper layer film while suppressing the occurrence of overlay errors during exposure. This makes it possible to design a pattern without considering the overlay margin, enabling the formation of a fine pattern and reducing the workload of the designer.
It can also contribute to cost reduction in the manufacturing process.

In addition, in the method for manufacturing a photomask according to the present invention , the lower layer film is a half-tone film , and in the first etching step, the upper layer film and the lower layer film are wet-etched.

By using this method of manufacturing a photomask, it is possible to manufacture a half-tone mask, which is a multi-tone mask.

Further, a method for producing a photomask according to the present invention includes the steps of:
The underlayer film is characterized in that it is a phase shift film.

By using this method for manufacturing a photomask, a phase shift mask can be manufactured.

The present invention provides a method for manufacturing a photomask that can form patterns with different optical characteristics while suppressing the occurrence of overlay errors during exposure.

3A to 3C are cross-sectional views showing main manufacturing steps of the photomask in the first embodiment. 3A to 3C are cross-sectional views showing main manufacturing steps of the photomask in the first embodiment. 1 is a SEM photograph showing a cross section of a photoresist film. 3A to 3C are cross-sectional views showing main manufacturing steps of the photomask in the first embodiment. 10A to 10C are cross-sectional views showing main manufacturing steps of a photomask in accordance with a second embodiment. 10A to 10C are cross-sectional views showing main manufacturing steps of a photomask in accordance with a second embodiment.

The following describes embodiments of the present invention with reference to the drawings. However, none of the following embodiments should be interpreted in a restrictive manner in determining the gist of the present invention. In addition, the same reference symbols are used for identical or similar components, and descriptions may be omitted.

(Embodiment 1)
1 and 2 are cross-sectional views showing main steps of manufacturing a photomask 100 according to embodiment 1. The method of manufacturing the photomask 100 will be described below with reference to the drawings.

(Deposition process: photomask blanks preparation process)
As shown in FIG. 1A, a transparent substrate 1 such as synthetic quartz glass is prepared, and a semi-transparent underlayer film 2 made of a known material such as a Cr-based metal compound, a Si-based compound, or a metal silicide compound is formed on the transparent substrate 1 by a sputtering method, a deposition method, or the like (for example, a film thickness of 5 nm to 20 nm).

Here, the transparent substrate 1 has a transmittance of 90 to 100% (90%≦transmittance≦100%) for representative wavelengths (e.g., i-line, h-line, g-line) contained in the exposure light used in the lithography process using the photomask 100.
Further, semi-transparent means that the transmittance for a representative wavelength contained in the exposure light is lower than that of the transparent substrate 1 and higher than that of a laminated structure film described later.
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. The exposure light is not limited to these.

The underlayer film 2 can be used as a halftone film or a phase shift film.
For example, when the lower layer 2 is used as a halftone film, the transmittance of the lower layer 2 is set to 10 to 70% (10%≦transmittance≦70%) for the representative wavelength. Also, the phase shift amount may be set small (approximately 0°, e.g., 0 to 20°).
Furthermore, for example, when the underlayer film 2 is used as a phase shift film, the transmittance of the underlayer film 2 is set to 3 to 15% (3%≦transmittance≦15%) and the phase shift amount is set to approximately 180° (160°≦phase shift amount≦200°), and more preferably 170°≦phase shift amount≦190°, for the representative wavelength contained in the exposure light.
The optical properties of the underlayer film 2 as a halftone film and a phase shift film can be realized by adjusting the composition and film thickness, for example.

Next, an upper layer 3 made of a known material such as a Cr-based metal compound, a Si-based compound, or a metal silicide compound is formed on the lower layer 2 by sputtering, vapor deposition, or the like (for example, to a thickness of 50 nm to 100 nm). However, the upper layer 3 is made of a material having different etching characteristics from the lower layer 2. For example, a combination is selected in which the lower layer 2 is made of a Cr-based compound and the upper layer 3 is made of a metal-based compound other than Cr, such as a Ti-based compound or a Ni-based compound. Note that the metal-based compound such as the Cr-based compound may be made of metal only.
The transmittance of the upper layer film 3 at the representative wavelength may be adjusted by adjusting the material (composition) and film thickness of the upper layer film 3 so that the laminated film of the upper layer film 3 and the lower layer film 2 has light shielding properties. The transmittance of this laminated film at the representative wavelength is, for example, 1% or less (0%≦transmittance≦1%). In other words, the optical density (OD value) may be set to 3.0 or more by adjusting the material (composition) and film thickness of the light shielding film 4 in the laminated region of the functional film 2, the etching stopper film 3, and the light shielding film 4.

Hereinafter, the laminated structure in which the lower layer film 2 and the upper layer film 3 are formed on the transparent substrate 1 will be referred to as a photomask blank.
A plurality of photomask blanks having the above-described configuration may be prepared and stored in advance. When an order is received from a customer or the like, the prepared photomask blanks having the above-described configuration can be used, which contributes to shortening the construction period.

(Photoresist formation process)
Next, as shown in FIG. 1B, a (photo)resist film 4 is formed on the upper layer 3 by a coating method, a spray method or the like.

(Exposure process)
Next, as shown in FIG. 1C, the photomask blanks are loaded (placed on an exposure stage in the exposure device) into an exposure (drawing) device (for example, a laser drawing device), and the resist film 4 is exposed.
At this time, three regions having different exposure doses are formed in the resist film 4, namely, a high dose region 4c (first region), a low dose region 4b (second region), and an unexposed region 4a (third region).
Here, the unexposed region 4a is a region that is not exposed, i.e., a region with an exposure dose of 0, the low dose region 4b is a region that is exposed with a relatively low exposure dose, and the high dose region 4c is a region that is exposed with a relatively high exposure dose.
The method of drawing using the exposure apparatus is not limited to laser drawing, and for example, an electron beam may be used.

More specifically, the high dose in the high dose region means an exposure amount equal to or greater than the exposure amount required to dissolve the resist when the resist is removed in the first developing step described below. In contrast, the low dose in the low dose region means an exposure amount at which the resist is not removed but left behind in the first developing step described below and is removed in the second developing step. For example, when the high dose required for the first developing step is used as a standard, the low dose means an exposure amount in the range of 5% to 90% of the high dose.
The low dose can be appropriately set within the above range, but it goes without saying that the process time of the second development step must be taken into consideration.

For simplicity, the high dose region 4c of the resist film 4 may be referred to as the "high dose region 4c", the low dose region 4b of the resist film 4 as the "low dose region 4b", and the unexposed region 4a of the resist film 4 as the "unexposed region 4a".

The low dose region 4b and the high dose region 4c can be formed without unloading (removing) the transparent substrate 1 from the exposure device. For example, the region corresponding to the low dose region 4b and the region corresponding to the high dose region 4c can be exposed by scanning the laser to a first exposure amount and a second exposure amount, respectively, to form these regions.

Alternatively, the regions corresponding to the low dose region 4b and the high dose region 4c may be exposed by scanning with a laser to a first exposure amount, and then only the region corresponding to the high dose region 4c may be additionally exposed by scanning with a laser to a second exposure amount for the high dose region 4c. The exposure amount is averaged by multiple laser irradiations, improving the uniformity of the exposure amount for the high dose region 4c. Furthermore, when the low dose region 4b and the high dose region 4c are in contact, the uniformity of the exposure amount at the boundary region is also improved.

As described above, the exposure process of the low dose region 4b and the high dose region 4c is performed without unloading the photomask blank from the exposure device, so that the occurrence of overlay errors (misalignment) between these regions (patterns) is suppressed.

(First development (resist removal) process)
Next, as shown in FIG. 1D, in a first development step, only the resist film 4 in the high dose region 4c is selectively removed by using a developer, thereby patterning the resist film 4.
As described later, since the dissolution characteristics of the resist film 4 in a developer depend on the exposure dose, it becomes possible to selectively and sequentially remove the resist film 4 exposed according to the exposure dose. In the first development step, development (dissolution in a developer) is performed under development conditions in which the dissolution rate of the high dose region 4c is sufficiently (for example, several times to one order of magnitude) higher than the dissolution rates of the unexposed region 4a and the low dose region 4b, so that only the high dose region 4c can be selectively removed.
As shown in FIG. 1D, the resist film thickness in the low dose region 4b is thinner than that in the unexposed region 4a.

(First Etching Step)
Next, as shown in FIG. 2( a ), the patterned resist film 4, i.e., the resist film 4 in the unexposed region 4 a and the low dose region 4 b, is used as an etching mask to etch the upper layer film 3 by a wet etching method or a dry etching method, and then the lower layer film 2 is etched by a wet etching method or a dry etching method to expose the surface of the transparent substrate 1.
By using different materials for the upper film 3 and the lower film 2, the upper film 3 can be selectively etched using an etchant (chemical solution or gas) that does not etch the lower film 2. Then, the lower film 2 can be selectively etched using an etchant (chemical solution or gas) that does not etch the upper film 3.

(Second Development (Resist Removal) Process)
2B, in a second development step, only the resist film 4 in the low dose region 4b is selectively removed by a developer, thereby patterning the resist film 4. In this step, only the unexposed region 4a is left on the upper layer film 3.
The reason why the resist film 4 with different exposure doses can be removed sequentially depending on the exposure dose as shown in the first and second development steps is that there is a phenomenon in which the dissolution rate depends nonlinearly on the development conditions (time, etc.) By utilizing the characteristic that the change point at which the dissolution rate changes (increases) depends on the exposure dose, the areas with different exposure doses can be selectively removed sequentially.
In the second development step, development (dissolution) is performed under development conditions in which the dissolution rate of the low dose regions 4b is sufficiently higher than the dissolution rate of the unexposed regions 4a, so that only the low dose regions 4b can be selectively removed.

In addition, by using this method, it is also possible to obtain three or more different resist film 4 patterns.

(Second Etching Step)
Next, as shown in FIG. 2(c), the unexposed region 4a is used as an etching mask, and the upper layer film 3 is selectively etched by wet etching or dry etching using an etchant (chemical solution or gas) that does not etch the lower layer film 2.
In FIG. 2C, a pattern constituted by a laminate of a lower layer film 2 and an upper layer film 3 is formed on both sides of the pattern constituted by only the lower layer film 2 .
The pattern formed only from the lower film 2 is determined by the low dose region 4b, and therefore can be optically set in the exposure step shown in FIG.

(Third resist removal process)
Next, as shown in FIG. 2D, the resist film 4 in the unexposed area 4a is removed by ashing or by immersion in a resist remover.
As a result of the above, a photomask 100 can be obtained, which has a light-shielding area 5 composed of a laminate including a lower layer film 2 and an upper layer film 3, a semi-transparent area 6 composed of the lower layer film 2, and a transparent area 7 in which the transparent substrate 1 is exposed.
The photomask 100 functions as a multi-tone halftone mask by adopting the above-mentioned conditions for the halftone film as the underlayer film 2. The photomask 100 can also function as a phase shift mask by adopting the above-mentioned conditions for the phase shift film as the underlayer film 2. In particular, in this case, since the occurrence of overlay errors in the exposure process is suppressed, rim portions of the semi-transmitting region 6 can be provided symmetrically on both sides of the light-shielding region 5, and a phase shift mask that enables the formation of fine patterns can be obtained.

Figure 3 is an SEM photograph showing the cross-sectional shape of the photoresist. Figure 3(a) shows the cross-sectional shape of the resist film 4 after the first development process, and Figure 3(b) shows the cross-sectional shape of the resist film 4 after the second development process.

As shown in FIG. 3A, at the boundary portion where the unexposed region 4a and the low-dose region 4b contact each other, the cross section of the resist film 4 may have a gently tapered shape.
However, as shown in Fig. 3(b), after the second development step, the cross section of the resist film 4 in the unexposed region 4a shows a steep shape. That is, the resist film 4 in the low dose region 4b defined in the exposure step shown in Fig. 1(c) is selectively removed in the second development step, and the unexposed region 4a is optically and accurately defined.

Also, as shown in Fig. 4(c), it is possible to form the semi-transmitting region 6 and the light-shielding region 5 apart from each other. As shown in Fig. 4(a), an exposure (writing) device exposes the resist film 4 to form an unexposed region 4a and a low-dose region 4b apart from each other, and then, as shown in Fig. 4(b), a first development step can be performed to obtain the unexposed region 4a and the low-dose region 4b apart from each other.
Thereafter, the semi-transmitting area 6 and the light-shielding area 5 can be formed separately from each other by the process shown in FIG.
Therefore, the light-shielding regions 5 and the semi-transmitting regions 6 can be set to an optically desired pattern, and the degree of freedom in designing the pattern of the photomask 100 is greatly improved as compared to the methods disclosed in Patent Documents 1 and 2.
It is also possible to adopt a pattern arrangement in which a pattern in which the semi-transmitting region 6 and the light-shielding region 7 are separated from each other and a pattern in which the semi-transmitting region 6 and the light-shielding region 7 are adjacent to each other are mixed.
The pattern arrangement of the semi-transmitting regions 6 and the light-shielding regions 7 can be varied in various ways as described above, and this also applies to the other embodiments.

(Embodiment 2)
In the first embodiment, it has been shown that a single exposure process can form three types of regions in the resist film 4, namely, the unexposed region 4a, the low dose region 4b, and the high dose region 4c, thereby manufacturing a photomask with three gradations, namely, the transparent region, the semi-transparent region, and the light-shielding region.
According to the second embodiment, it is also possible to provide a photomask 100 with even more tones.

As shown in FIG. 5(a), the resist film 4 is exposed in a single exposure process to form a first region 4d, a second region 4e, a third region 4f, and a fourth region 4g (exposure amount 0) in descending order of exposure dose.

Next, as shown in FIG. 5(b), the first region 4d, which has the greatest amount of exposure, is selectively removed, and then the upper layer film 3 and the lower layer film 2 are etched using the resist film 4 in the second region 4e, the third region 4f, and the fourth region 4g as a mask, to expose the transparent substrate 1.

Next, as shown in FIG. 5(c), the second region 4e, which has the second highest exposure dose, is selectively removed, and then the upper layer film 3 is removed by etching using the resist film 4 in the third region 4f and the fourth region 4g as a mask, and the lower layer film 2 is further partially etched to form a first lower layer film 2a (thin lower layer film 2a) that is relatively thin and a second lower layer film 2b (thick lower layer film 2b) that is relatively thick.

Next, as shown in FIG. 5(d), the third region 4f, which has the third highest exposure dose, is selectively removed, and then the upper layer film 3 is etched and removed using the resist film 4 in the fourth region 4g as a mask, exposing the surface of the second lower layer film 2b.

Next, as shown in FIG. 5(e), the resist film 4 in the fourth region 4g is removed by ashing or by immersion in a resist remover.
A light-shielding region 5 which is a laminate of a lower layer film 2 and an upper layer film 3, a transparent region 7 where the transparent substrate 1 is exposed, a first semi-transparent region 61 which is composed of a first lower layer film 2a having a relatively thin thickness, and a second semi-transparent region 62 which is composed of a second lower layer film 2b having a relatively thick thickness are formed.
Therefore, a photomask 100 with four gradations can be obtained, which includes the transmissive region 7, the light-shielding region 5, and the first semi-transmissive region 61 and the second semi-transmissive region 62 having different transmittances.

Alternatively, a semi-transparent region may be formed by partially etching a portion of the upper layer 3 to reduce its thickness.
In the step shown in Fig. 5(c), the second region 4e, which has the second highest exposure dose, is selectively removed, and then, using the resist film 4 in the third region 4f and the fourth region 4g as a mask, only the upper layer film 3 is selectively etched and removed, as in the step shown in Fig. 2(c), to expose the surface of the lower layer film 2 (see Fig. 6(a)).

Next, as shown in FIG. 6(b), the third region 4f having the third highest exposure dose is selectively removed, and then the upper layer film 3 is partially etched using the resist film 4 in the fourth region 4g as a mask to form a first upper layer film 3a (thin film upper layer film 3a) having a relatively thin thickness and a second upper layer film 3b (thick film upper layer film 3b) having a relatively thick thickness.
The thin upper layer film 3a obtained by reducing the film thickness of the upper layer film 3 has an increased transmittance for the representative wavelength, and serves as a semi-transparent film.

Next, as shown in FIG. 6C, the resist film 4 in the fourth region 4g is removed by an ashing method or by immersion in a resist remover.
The transparent region 7 where the transparent substrate 1 is exposed, the first semi-transmitting region 61 composed of the lower layer film 2, the second semi-transmitting region 62 composed of the lower layer film 2 and the first upper layer film 3a having a relatively thin thickness, and the light-shielding region 5 which is the laminate of the lower layer film 2 and the second upper layer film 3b having a relatively thick thickness are formed. The second semi-transmitting region 62 has a lower transmittance than the first semi-transmitting region 61 because it has the first upper layer film 3a (thin upper layer film 3a) on the upper layer of the lower layer film 2. In addition, the first upper layer film 3a is thinner than the upper layer film 3 and has an increased transmittance, so the second semi-transmitting region 62 is a semi-transmitting region with a higher transmittance than the light-shielding region 5 (lamination of the lower layer film 2 and the thick upper layer film 3b).
Therefore, a four-tone photomask 100 can be obtained, which includes the transmissive region 7, the first semi-transmissive region 61, the second semi-transmissive region 62, and the light-shielding region 5, each of which has a different transmittance.

In this way, the transmittance can be changed by reducing the film thickness in some regions of the lower layer film 2 or the upper layer film 3, and a photomask 100 with even more gradations can be obtained. Furthermore, by combining the manufacturing process shown in FIG. 5 with the manufacturing process shown in FIG. 6, the transmittance can be changed by reducing the film thickness in some regions of the lower layer film 2 and the upper layer film 3, and a multi-gradation photomask 100 can be obtained.

In the above embodiments, a positive resist is used as the resist film 4, but the same applies when a negative resist is used. In the case of a negative resist, the relationship of the exposure amount is opposite to that of a positive resist. For example, the unexposed area of the positive resist corresponds to the high dose area of the negative resist, and the high dose area of the positive resist corresponds to the unexposed area of the negative resist.

According to the present invention, a photomask having patterns with different optical characteristics can be obtained by a single exposure process, and as a result, a fine pattern can be realized while preventing an increase in the number of steps required for manufacturing the photomask.
Use of this photomask in the production process of products such as display devices can contribute to improving the performance of the products, and the industrial applicability is great.

1 Transparent substrate 2 Underlayer film 2a First underlayer film (thin underlayer film)
2b Second underlayer film (thick underlayer film)
3 Upper layer film 3a First upper layer film (thin upper layer film)
3b Second upper layer film (thick upper layer film)
4 (photo)resist film 4a unexposed area (third area)
4b Low dose region (second region)
4c High dose region (first region)
4d first region 4e second region 4f third region 4g fourth region 5 light-shielding region 6 semi-transmitting region 61 first semi-transmitting region 62 second semi-transmitting region 7 transmitting region 100 photomask

Claims (6)

preparing a photomask blank having an underlayer film on a transparent substrate and an upper layer film on the underlayer film;
forming a resist film on the upper layer film;
an exposure step of exposing the resist film to light and scanning the resist film with a laser to form a first region, a second region, and a third region having different exposure amounts, so that the second region is symmetrically disposed on both sides of the third region;
a first resist removal step of selectively removing the first region with a developer ;
a first etching step of etching the upper layer film and the lower layer film;
a second resist removal step of selectively removing the second region with a developer ;
a second etching step of etching the upper layer film;
removing the third region;
The method for manufacturing a photomask is characterized in that the underlayer film has a transmittance of 3 to 15% and a phase shift amount of approximately 180°. preparing a photomask blank having an underlayer film on a transparent substrate and an upper layer film on the underlayer film;
forming a resist film on the upper layer film;
an exposure step of exposing the resist film to light to form a first region, a second region, and a third region having different exposure amounts, and configuring the second region to be symmetrically disposed on both sides of the third region;
a first resist removal step of selectively removing the first region;
a first etching step of etching the upper layer film and the lower layer film;
a second resist removal step of selectively removing the second region;
a second etching step of etching the upper layer film to form a laminated pattern of the upper layer film and the lower layer film, and forming a rim portion of the laminated pattern consisting of only the lower layer film;
removing the third region;
The underlayer film has a transmittance of 3 to 15% and a phase shift of approximately 180°.
The laminated pattern has a light-shielding property.
A method for manufacturing a photomask comprising the steps of: preparing a photomask blank having an underlayer film on a transparent substrate and an upper layer film on the underlayer film;
forming a resist film on the upper layer film;
an exposure step of exposing the resist film to light to form a first region, a second region , a third region , and a fourth region having different exposure doses;
a first resist removal step of selectively removing the first region;
a first etching step of etching the upper film and the lower film using the second region, the third region, and the fourth region as a mask ;
a second resist removal step of selectively removing the second region;
a second etching step of etching the upper layer film using the third region and the fourth region as a mask , and further etching the lower layer film partially to reduce the film thickness;
a third resist removal step of removing the third region ;
a third etching step of etching the upper layer film using the fourth region as a mask;
a fourth resist removal step of removing the fourth region;
A method for manufacturing a photomask, comprising: 4. The method of manufacturing a photomask according to claim 1, wherein the lower film and the upper film are made of different materials. The method for manufacturing a photomask according to claim 1 or 2, characterized in that in the exposure step, the exposure amount of the first region is greater than the exposure amount of the second region, and the exposure amount of the third region is zero. 4. The method for manufacturing a photomask according to claim 1, wherein the upper film and the lower film are wet-etched in the first etching step.

Images