Photomask

Abstract

The present invention provides a photomask capable of stably resolving a fine hole pattern. The photomask comprises: a transmissive portion exposing a transmissive substrate; and a first phase shift portion and a second phase shift portion surrounding the transmissive portion and inverting the phase of exposure light. The second phase shift portion is interposed between the first phase shift portion and the transmissive portion, and the transmittance of the second phase shift portion to the exposure light is lower than the transmittance of the first phase shift portion. In addition, the second phase shift portion can be constituted by a laminated structure of a phase shift film of the first phase shift portion and a semi-transmissive film.

Description

Technical Field

[0001] The present invention relates to a photomask used in a photolithography process. Background Art

[0002] Photomasks are used in the photolithography process for manufacturing electronic devices such as flat panel displays. Conventionally, photomasks used for transferring hole patterns to photoresists use binary masks having light-shielding portions and transmissive portions, with the portion corresponding to the hole pattern being the transmissive portion.

[0003] In recent years, for example, in order to form a fine hole pattern of less than 2 [μm], a phase shift mask has been proposed as a photomask for patterning holes. It is known that the phase shift mask has not only an effect of improving the resolution but also an effect of improving the depth of focus (DOF) compared to the conventional binary mask. (For example, refer to the fourth paragraph of Patent Document 1)

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-163335 Summary of the invention

[0007] Problems to be solved by the invention

[0008] However, when a phase shift mask is used to transfer a fine hole pattern to a photoresist, although the depth of focus can be improved, a high exposure dose is required, which increases the exposure time and the tact time of the exposure device.

[0009] Therefore, conventional photomasks cannot fully meet the stricter requirements for actual use conditions in the photolithography process for manufacturing electronic devices.

[0010] Furthermore, since a DOF one order of magnitude higher than that required in the manufacturing process of semiconductor devices such as LSI is required, such a strict requirement cannot be met even by the miniaturization technology (semiconductor process technology) used in the manufacturing of semiconductor devices.

[0011] In view of the above problems, an object of the present invention is to provide a photomask capable of stably resolving a fine hole pattern.

[0012] Means for solving problems

[0013] The photomask according to the present invention is characterized in that it comprises a transmission portion, a first phase shift portion, and a second phase shift portion.

[0014] The first phase shift portion and the second phase shift portion surround the transmission portion.

[0015] The second phase shift portion is interposed between the first phase shift portion and the transmission portion.

[0016] The second phase shifter and the first phase shifter invert the phase of the exposure light.

[0017] The transmittance of the second phase shift portion is lower than the transmittance of the first phase shift portion.

[0018] In addition, the photomask according to the present invention is characterized in that the transmittance of the first phase shift portion is 8 to 15%, and the transmittance of the second phase shift portion is 3 to 7%.

[0019] In addition, the photomask according to the present invention is characterized in that the phase shift amounts of the first phase shift portion and the second phase shift portion are in a range of 160[°] to 210[°].

[0020] By adopting such a configuration, it is possible to provide a photomask capable of improving DOF and required exposure amount in a photolithography process.

[0021] In addition, the photomask according to the present invention is characterized in that the phase shift amount of the first phase shift portion is in the range of 160[°] to 190[°], and the phase shift amount of the second phase shift portion is in the range of 180[°] to 210[°].

[0022] With such a configuration, it is easy to adjust the phase shift amounts of the first phase shifter and the second phase shifter.

[0023] In the photomask according to the present invention, the second phase shift portion is a stack of a phase shift film and a semi-transmissive film constituting the first phase shift portion.

[0024] With such a configuration, the photomask can be easily manufactured.

[0025] Effects of the Invention

[0026] According to the present invention, a photomask capable of stably resolving a fine hole pattern can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 (a) is a top view of the photomask of Embodiment 1, Figure 1 (b) Figure 1 (c) is a graph for explaining the effect of improving the lithography characteristics (DOF and required exposure amount).

[0028] Figure 2 (a) Figure 2 (b) is a cross-sectional view showing the main steps of the photomask of Embodiment 1, Figure 2 (c) is its top view.

[0029] Figure 3 (a)~ Figure 3 (c) is a cross-sectional view showing the main steps of the photomask of the first embodiment. Figure 3 (d) is its top view.

[0030] Figure 4 It is a cross-sectional view showing main steps of the photomask according to the second embodiment.

[0031] Figure 5 (a) is a cross-sectional view showing the main steps of the photomask of Embodiment 2, Figure 5 (b) is a top view thereof. DETAILED DESCRIPTION

[0032] Hereinafter, the embodiments of the present invention will be described with reference to the accompanying drawings. However, the following embodiments are not intended to be construed as limiting the purpose of the present invention. In addition, the same reference numerals are sometimes used to mark the same or similar components and the description thereof is omitted.

[0033] (Implementation Method 1)

[0034] Figure 1 (a) is a top view showing a photomask 100 according to the present invention. Figure 1 (b) Figure 1 (c) is a graph illustrating the improvement effect of the present photomask 100 on the DOF and the required exposure amount when exposing the photoresist. By using the photomask 100 in the photolithography process, micropores (especially 1.5 [μm] to 2.0 [μm] in size) can be stably resolved on the photoresist to be exposed.

[0035] The photomask 100 has a first phase shift portion 102 formed so as to surround a transmission portion 101 for forming a hole pattern on a resist, and a second phase shift portion (flange (outer edge) portion) 103 is interposed between the transmission portion 101 (opening portion) and the first phase shift portion 102. Therefore, the transmission portion 101 is in contact with the second phase shift portion 103, and the second phase shift portion 103 is in contact with the first phase shift portion 102.

[0036] The first phase shifter 102 and the second phase shifter 103 have a phase shift amount capable of inverting exposure light used in a photolithography process for manufacturing electronic devices.

[0037] The width R of the second phase shift portion (refer to Figure 1) is 0 [μm] < R ≤ 1 [μm], and more preferably 0.5 [μm] ≤ R ≤ 1 [μm]. The second phase shift portion (flange portion) 103 has a lower transmittance to the exposure light than the first phase shift portion 102. That is, a low-transmittance phase shift portion (second phase shift portion 103) and a high-transmittance phase shift portion (first phase shift portion 102) are formed in a manner that sequentially surrounds the periphery of the transparent portion 101 of the hole opening pattern.

[0038] The transmittance of the transmission portion 101 to the exposure light (i-ray) in the photolithography process is 90 to 100% (90%≤transmittance≤100%), and depends on the transparent substrate of the photomask.

[0039] The phase shift amount (phase difference) of the first phase shifter 102 with respect to the exposure light (i-ray) is approximately 180[°], and the transmittance is 8 to 15% (8%≤transmittance≤15%).

[0040] The phase shift amount of the second phase shifter 103 with respect to the exposure light (i-ray) is approximately 180[°], and the transmittance is 3 to 7% (3%≤transmittance≤7%).

[0041] As described above, the first phase shifter 102 and the second phase shifter 103 both reverse the phase of the exposure light by approximately 180° (specifically, 160°≤phase shift≤210°).

[0042] As described later, for example, when the first phase shift portion 102 is composed of a single-layer structure and the second phase shift portion 103 is composed of a stacked structure, the phase shift amounts of the first phase shift portion 102 and the second phase shift portion 103 can be set to, for example, 160[°]≤phase shift amount≤190[°] and 180[°]≤phase shift amount≤210[°]. By setting the specifications of these phase shift amounts, it is easy to adjust the phase shift amounts of the first phase shift portion 102 and the second phase shift portion 103, and it is also easy to manufacture a photomask.

[0043] The required DOF value of the semiconductor process for manufacturing LSI with fine patterns is at most about 1 [μm]. In contrast, in the photolithography process of electronic devices such as flat panel displays, for example, in the case of stably transferring the pattern of holes with a size of less than 2.0 [μm], the required DOF is more than 10 times higher than the DOF value of the semiconductor process.

[0044] According to the present invention, it has been confirmed that such stringent conditions can be satisfied, and further, it has been confirmed that a further reduction effect can be obtained compared with the minimum required exposure (EOP) disclosed in Patent Document 1.

[0045] Furthermore, the width R of the second phase shift portion 103 was investigated, and it was confirmed that a particularly preferable width R is 0.5 to 1.0 [μm].

[0046] The improvement effect of DOF and EOP is shown in Figure 1 (b) Figure 1 (c) Figure 1 (b) Figure 1 (c) is a graph showing the conditional dependence of DOF and required exposure (EOP) when a hole pattern having a size of 2 [μm] is formed on a photoresist film to have a size substantially equal to S (side length) on a mask. Figure 1 (b) Figure 1 “DOF” and “EOP” on the vertical axis of the graph of (c) represent ratios to the DOF and EOP of a conventional binary mask formed of a transmission portion and a light shielding portion, respectively.

[0047] exist Figure 1 (b) Figure 1 In (c), "PS" refers to a photomask using a single-layer (without the second phase shifter 103) phase shift film having a transmittance of 5% to exposure light (i-ray). "PS+PS-Rim" refers to a photomask having a first phase shifter 102 with high transmittance and a second phase shifter 103 with low transmittance, wherein the transmittance of the first phase shifter 102 is 12% and the transmittance of the second phase shifter 103 is 5%.

[0048] It should be noted that the phase shift amount is 180[°].

[0049] In the case of "PS", DOF is increased to about 1.5 times compared to the conventional binary mask, and an improvement effect is confirmed, but there is a problem that EOP is increased to 1.3 times.

[0050] In the case of "PS+PS-Rim", DOF was confirmed to be increased by about 1.9 times compared with the conventional binary mask, and even compared with "PS", it has a further improvement effect. On the other hand, EOP is about 1.1 times, which is equivalent to the conventional binary mask.

[0051] That is, it was confirmed that the photomask including the first phase shift portion 102 and the second phase shift portion 103 can suppress (reduce) the increase in the required exposure amount and obtain a significant improvement effect of DOF.

[0052] In addition, by setting the transmittance of the second phase shifter 103 to 5% and increasing the transmittance of the first phase shifter 102 in the range of 8 to 15%, it was confirmed that DOF tended to increase and EOP hardly changed (instead, slightly decreased). Therefore, there is a margin for transmittance (for example, a margin for the uniformity of transmittance within the plane of the photomask), and stable exposure conditions can be achieved.

[0053] The above tendency also holds true when the transmittance of the second phase shifter 103 is in the range of 3% to 7%.

[0054] On the other hand, in the case of a phase shift mask using only a single-layer phase shift film without the second phase shift portion 103 having low transmittance, it was confirmed that EOP is highly dependent on the transmittance of the phase shift film and is easily affected by changes in the transmittance of the phase shift film.

[0055] Thus, the photomask 100 has a sufficiently high DOF, which can ensure a sufficient margin for the photolithography process for the film thickness of the resist. Furthermore, the increase in the exposure amount required for the hole opening can be suppressed. Therefore, the requirements for the photolithography process when manufacturing electronic devices can be met and a hole pattern can be stably formed on the resist film.

[0056] It should be noted that, although the exposure light is described as i-ray, the exposure light is not limited to i-ray, and may be i-ray, h-ray, g-ray, or a mixture thereof. The phase shift amount and transmittance may be set in accordance with the representative wavelength of the exposure light. It should be noted that the same is true for other embodiments.

[0057] Hereinafter, a process of manufacturing the photomask 100 according to the present embodiment will be described in detail.

[0058] like Figure 2 As shown in (a), a transparent substrate 1 such as synthetic quartz glass is prepared, and a semi-transparent film 2 (half-tone film) made of, for example, a Cr-based metal compound is formed on the transparent substrate 1 (e.g., film thickness 5 [nm] to 20 [nm]) by sputtering, evaporation, etc.

[0059] At this time, the transmittance of the semi-transmissive film 2 to the exposure light (i-ray) is set to 40 to 70% by adjusting the composition and the film thickness, for example.

[0060] Then, if Figure 2 As shown in (b), a (photolithography) resist film is formed on the semi-permeable membrane 2, and the resist film is patterned by exposure and development processes. Then, the semi-permeable membrane 2 is etched by wet etching or dry etching using the patterned resist film as a mask to form a pattern 3 formed by the semi-permeable membrane 2. Then, the resist film is removed by ashing or immersion in a resist stripping solution.

[0061] The width of the cross section of pattern 3 is set to Figure 1 (a) shows the width R of the second phase shift portion.

[0062] In addition, for the subsequent photolithography, the semi-transmissive film 2 may be patterned to appropriately form an alignment mark.

[0063] Figure 2 (c) Yes Figure 2 (b) is a top view of the photomask 100 in the process shown, and shows the outline (layout) of the pattern 3. The pattern 3 is formed in the form of a flange portion (outer edge portion) surrounding the periphery of the opening portion 4 for forming a hole pattern.

[0064] For example, when a hole pattern of 2.0 [μm] is transferred to a photoresist film, a preferred size S (side length) of the opening 4 of the photomask 100 is 2.2 to 2.4 [μm].

[0065] Then, if Figure 3 As shown in (a), a phase shift film 5 (phase reversal film) made of, for example, a Cr-based metal compound is formed by sputtering, vapor deposition, etc. (e.g., film thickness 50 [nm] to 100 [nm]). The composition and film thickness are adjusted so that the transmittance of the phase shift film 5 to the exposure light (i-ray) is 8 to 15% and the phase shift amount is 160 to 190 [°].

[0066] For example, the pattern 3 (semi-permeable film 2) and the phase shift film 5 may preferably be made of the same film type (same composition), or may be made of different film types, such as a Ti-based metal compound.

[0067] Then, if Figure 3 As shown in (b), a resist film 6 is formed and patterned by exposure and development processes. In this process, the resist film 6 is removed at a location corresponding to the opening 4. That is, the patterned resist film 6 exposes the phase shift film 5 in a region surrounded by the pattern 3.

[0068] Then, if Figure 3 As shown in (c), the phase shift film 5 is etched and patterned by wet etching or dry etching using the patterned resist film 6 as a mask. Thereafter, the resist film 6 is removed by ashing or immersion in a resist stripping solution.

[0069] like Figure 3 As shown in (c), a first phase shift region 7 formed by the phase shift film 5 and a second phase shift region 8 formed by laminating the semi-transmissive film 2 and the phase shift film 5 constituting the pattern 3 are formed. In addition, in the opening 4, the transparent substrate 1 is exposed.

[0070] Figure 3 (d) Yes Figure 3(c) is a top view of the photomask in the process shown in FIG. The second phase shift region 8 is formed so as to surround the opening 4, and further, the first phase shift region 7 is formed so as to surround the second phase shift region 8. Therefore, the inner periphery of the second phase shift region 8 is in contact with the outer periphery of the opening 4, and the inner periphery of the first phase shift region 7 is in contact with the outer periphery of the second phase shift region 8.

[0071] The first phase shift region 7 corresponds to Figure 1 The second phase shift region 8 corresponds to the first phase shift portion 102 , the second phase shift region 8 corresponds to the second phase shift portion 103 , and the opening 4 corresponds to the transmission portion 101 .

[0072] The first phase shift region 7 is formed of the phase shift film 5, and has a transmittance of 8 to 15% for exposure light and a phase shift amount of 160 to 190[°].

[0073] The second phase shift region 8 is formed by stacking the semi-permeable film 2 and the phase shift film 5, and has a transmittance of 3 to 7% for exposure light and a phase shift amount of 180 to 210 [°]. The phase shift amount of the semi-permeable film 2 itself is not particularly limited as long as the phase shift amount of the stack of the semi-permeable film 2 and the phase shift film 5 can be set to 180 to 210 [°]. For example, the phase shift amount of the semi-permeable film 2 itself can be set to be smaller (approximately 0 [°], for example, 0 to 20 [°]). Even in the case where the semi-permeable film 2 and the phase shift film 5 are of the same film type, the phase shift amount at the semi-permeable film 2 can be set to be smaller (reduced film thickness), the phase shift amount in the second phase shift region 8 of the stacked structure can be set to approximately 180 [°], and the transmittance can be adjusted to be lower.

[0074] Representative film forming conditions are shown below. It is to be noted that the lower film refers to a film (in this case, the semi-permeable film 2) formed on the lower side (transmissive substrate 1 side) in the second phase shift region 8 of the stacked structure, and the upper film refers to a film (in this case, the phase shift film 5) formed on the upper side (on the lower film).

[0075] <Condition 1>

[0076] : Material: Film type: Film thickness: Transmittance: Phase difference Lower film: Cr compound: Halftone film: 7nm: 60%: - Upper film: Cr compound: Phase shift film: 75nm: 10%: 185° Lamination:: Lamination structure:: 5%: 194°

[0077] <Condition 2>

[0078] : Material: Film type: Film thickness: Transmittance: Phase difference Lower film: Cr compound: Halftone film: 15nm: 47%: - Upper film: Cr compound: Phase shift film: 67nm: 12%: 174° Lamination:: Lamination structure:: 5%: 185°

[0079] <Condition 3>

[0080] : Material: Film type: Film thickness: Transmittance: Phase difference Lower film: Cr compound: Halftone film: 17nm: 44%: - Upper film: Cr compound: Phase shift film: 62nm: 12%: 180° Lamination:: Lamination structure:: 5%: 200°

[0081] In the above example, the second phase shift region 8 having a low transmittance is formed by laminating the semi-transmissive film 2 and the phase shift film 5 , and most of the value of the phase shift amount is determined by the phase shift film 5 .

[0082] The phase shift film 5 can preferably use a wavelength-independent halftone film (so-called "FLAT film") having a low wavelength dependence of the phase shift amount, for example, a phase shift variation within 20[°]. However, since the above conditions are satisfied, it is not limited to a wavelength-independent halftone film. In addition, as for the semi-transmissive film 2, for example, a condition (film thickness, etc.) with a small phase shift amount can also be used, and there is no need to use a wavelength-independent halftone film in particular. Either a conventional semi-transmissive film (wavelength-dependent halftone film) or a wavelength-independent halftone film can be used.

[0083] It should be noted that the patterning method of the semi-transmissive film 2 and the phase shift film 5 is not limited to the above-mentioned method. Figure 2 , Figure 3 For example, in Figure 2 In the step (b), the semi-transmissive film 2 in the region corresponding to the first phase shift portion 102 is etched (i.e., the semi-transmissive film 2 in the region corresponding to the transparent portion 101 and the second phase shift portion 103 is left), and then the phase shift film 5 is formed. Figure 3 In the step (b), the stacked portion of the semi-transmissive film 2 and the phase shift film 5 in the region corresponding to the opening 4 (transmissive portion 101 ) may be etched.

[0084] It should be noted that the material of the semi-permeable membrane 2 and the phase shift membrane 5 is not limited to the Cr-based metal compound, and other known metal compounds may also be used.

[0085] (Implementation Method 2)

[0086] In the first embodiment described above, a method for manufacturing the photomask 100 is described in which the semi-transmissive film 2 is formed on the transparent substrate 1 and the phase shift film 5 is formed after patterning.

[0087] However, the semi-permeable membrane 2 may be formed after the phase shift film 5 is formed on the transparent substrate 1. That is, in the second phase shift portion 103, the vertical relationship between the semi-permeable membrane 2 and the phase shift film 5 may be reversed from that in the first embodiment.

[0088] Hereinafter, a manufacturing process of the photomask 100 according to the second embodiment will be described.

[0089] like Figure 4 As shown in (a), a phase shift film 5 (phase inversion film) is formed on a transparent substrate 1 by sputtering, vapor deposition, etc. The transmittance and phase shift amount of the phase shift film 5 are as described above.

[0090] Then, if Figure 4 As shown in (b), a semi-permeable film 2 is formed by a sputtering method, a vapor deposition method, or the like. The transmittance of the semi-permeable film 2 is as described above. Thereafter, a resist film 9 (first resist film) is formed, and the resist film 9 is patterned by an exposure and development process. In this process, the resist film 9 corresponding to the opening 4 is removed.

[0091] Then, if Figure 4 As shown in (c), the semi-permeable membrane 2 and the phase shift film 5 are etched by, for example, wet etching or dry etching using the resist film 9 as a mask. The opening 4 is formed in the semi-permeable membrane 2 and the phase shift film 5 to expose the transparent substrate 1. Thereafter, the resist film 9 is removed by ashing or immersion in a resist stripping solution.

[0092] In addition, for the subsequent photolithography, the stacked layers of the semi-transmissive film 2 and the phase shift film 5 may be patterned to appropriately form alignment marks.

[0093] Then, if Figure 4 As shown in (d), a resist film 10 (second resist film) is formed, and the resist film 10 is patterned by exposure and development process. The pattern of the resist film 10 is formed so as to surround the opening 4 and overlap with the laminated film of the semi-transmissive membrane 2 and the phase shift film 5. The overlap width is set to R. The resist film 10 of the pattern area consisting of the opening 4 and the second phase shift area 8 surrounding the opening 4 remains.

[0094] In addition, the overlap width can be set to a value obtained by adding the side etching amount to R in consideration of the side etching amount in the subsequent etching step of the semi-permeable membrane 2 .

[0095] Then, if Figure 5 As shown in (a), the semi-transmissive film 2 on the phase shift film 5 is etched by, for example, wet etching or dry etching using the resist film 10 as a mask. Thereafter, the resist film 10 is removed by ashing or immersion in a resist stripping solution.

[0096] In order to leave the phase shift film 5 and etch the semi-permeable film 2 on the phase shift film 5, the phase shift film 5 and the semi-permeable film 2 may preferably be made of different materials. For example, a combination in which one of the phase shift film 5 and the semi-permeable film 2 is made of a Cr-based metal compound and the other is made of a Ti-based metal compound may be used. As a result, the semi-permeable film 2 on the phase shift film 5 can be selectively etched.

[0097] Alternatively, the semipermeable membrane 2 on the phase shift film 5 may be removed by making the phase shift film 5 and the semipermeable membrane 2 consist of the same material and setting the etching time to be the same as the etching time of the semipermeable membrane 2 .

[0098] Figure 5 (b) Yes Figure 5 (a) Top view of the photomask.

[0099] The second phase shift region 8 having a width R is formed so as to surround the opening 4 , and further, the first phase shift region 7 is formed so as to surround the second phase shift region 8 .

[0100] and Figure 3 The second phase shift region 8 shown in (d) is different from the phase shift film 5 formed on the semi-transmissive film 2. Figure 5 In the second phase shift region 8 shown in (b), the semi-transmissive film 2 is formed on the phase shift film 5 .

[0101] It goes without saying that in the second embodiment, the effects of improving DOF and exposure amount can be obtained.

[0102] Compared with the photomask manufacturing method of the first embodiment, the photomask manufacturing method of the second embodiment forms the semi-transmissive film 2 on the flat phase shift film 5, so it is easy to form the semi-transmissive film 2. On the other hand, compared with the photomask manufacturing method of the first embodiment, the photomask manufacturing method of the second embodiment requires etching the film formed on the upper layer of the second phase shift region 8 on the film formed on the lower layer, so it is necessary to accurately control the etching.

[0103] In the second embodiment, the semi-permeable membrane 2 is formed on the phase shift membrane 5. However, when the phase shift membrane 5 and the semi-permeable membrane 2 are made of the same material, the phase shift membrane 51 having the same thickness as the sum of the thickness of the phase shift membrane 5 and the thickness of the semi-permeable membrane 2 may be formed without adopting a laminated structure. Figure 4 In the step (b), the stack of the phase shift film 5 and the semi-permeable membrane 2 is replaced with a single-layer phase shift film 51, and then etching is performed using the resist film 9. Figure 4 (c)~ Figure 5 The first phase shift region 7 and the second phase shift region 8 are formed by the step (a).

[0104] In this case, Figure 5 In step (a), the etching amount (etching time) of the phase shift film 51 is adjusted, and the second phase shift region 8 can be configured to be thicker than the first phase shift region 7 by a desired thickness. As a result, the transmittance of the second phase shift region 8 can be set lower than that of the first phase shift region 7 .

[0105] Industrial Applicability

[0106] According to the present invention, a photomask capable of stably resolving a fine hole pattern can be provided, and the photomask can be preferably used in the manufacturing process of electronic devices for display devices such as flat panel displays, and has great industrial applicability.

[0107] It can be particularly preferably used in a photolithography process that has a strict requirement on DOF, such as in the manufacture of electronic devices for display devices.

[0108] Description of Reference Numerals

[0109] 1 Transparent substrate

[0110] 2 Semi-permeable membrane

[0111] 3 Pattern

[0112] 4 Opening

[0113] 5 Phase shift film

[0114] 6. Resist film

[0115] 7 1st phase shift region

[0116] 8 Second phase shift region

[0117] 9 Resist film

[0118] 10. Resist film

[0119] 51 Phase shift film

[0120] 100 Photomask

[0121] 101 Transparent

[0122] 102 1st phase shifter

[0123] 103 Second phase shifter

Claims

1. A photomask, characterized in that: The invention comprises a transmission part, a first phase shift part and a second phase shift part, The first phase shift portion and the second phase shift portion surround the transmission portion. The second phase shift portion is interposed between the first phase shift portion and the transmission portion. The transmission portion is connected to the second phase shift portion, and the second phase shift portion is connected to the first phase shift portion. The second phase shifter and the first phase shifter invert the phase of the exposure light. The transmittance of the second phase shift portion is lower than the transmittance of the first phase shift portion. The transmittance of the first phase shift portion is 8 to 15%, and the transmittance of the second phase shift portion is 3 to 7%.

2. The photomask according to claim 1, wherein: The phase shift amounts of the first phase shifter and the second phase shifter are in a range of 160° to 210°.

3. The photomask according to claim 1, wherein: The phase shift amount of the first phase shifter is in the range of 160° to 190°. The phase shift amount of the second phase shifter is in a range of 180° to 210°.

4. The photomask according to any one of claims 1 to 3, wherein: The second phase shifter is a stack of a phase shift film and a semi-transmissive film constituting the first phase shifter.

Images