Photomask, method for manufacturing photomask, and method for manufacturing display device
阅读说明：本技术 光掩模、光掩模的制造方法以及显示装置的制造方法 (Photomask, method for manufacturing photomask, and method for manufacturing display device ) 是由 今敷修久 吉川裕 菅原浩幸 于 2015-07-16 设计创作，主要内容包括：本发明涉及光掩模、光掩模的制造方法、光掩模坯料以及显示装置的制造方法。有利地适于显示装置制造用掩膜的曝光环境、并且能够稳定地转印微小的图案。光掩模具有通过对成膜于透明基板上的半透光膜以及低透光膜分别进行图案化而形成的转印用图案,上述转印用图案具有：由露出上述透明基板的透光部构成的直径W1(μm)的主图案；配置于上述主图案的附近、由在上述透明基板上形成有上述半透光膜的半透光部构成的宽度d(μm)的辅助图案；以及配置于上述转印用图案的形成有上述主图案以及上述辅助图案以外的区域、在上述透明基板上至少形成有上述低透光膜的低透光部,上述主图案的直径W1、上述半透光部的透光率T1以及上述半透光部的宽度d具有规定的关系。(The invention relates to a photomask, a method for manufacturing the photomask, a photomask blank and a method for manufacturing a display device. Is advantageously suitable for the exposure environment of a mask for manufacturing a display device, and can stably transfer a minute pattern. The photomask has a transfer pattern formed by patterning a semi-light-transmitting film and a low-light-transmitting film formed on a transparent substrate, and the transfer pattern has: a main pattern having a diameter W1(μm) and including a light-transmitting portion exposing the transparent substrate; an auxiliary pattern having a width d (μm) and disposed in the vicinity of the main pattern and including a semi-transmissive portion having the semi-transmissive film formed on the transparent substrate; and a low light transmission portion disposed in a region of the transfer pattern other than the region where the main pattern and the auxiliary pattern are formed, the low light transmission portion having at least the low light transmission film formed on the transparent substrate, wherein a diameter W1 of the main pattern, a light transmission rate T1 of the semi-light transmission portion, and a width d of the semi-light transmission portion have a predetermined relationship.)
1. A photomask for manufacturing a display device, comprising a transfer pattern formed by patterning a semi-light-transmitting film and a light-shielding film formed on a transparent substrate, respectively,
for forming an independent hole pattern on a transferred object by exposure using an exposure device having an optical system with a numerical aperture NA of 0.08 to 0.20,
the semi-light-transmitting film shifts light of a representative wavelength of exposure light including i-line, h-line, or g-line by 150 to 210 degrees and has a transmittance T1 with respect to the representative wavelength,
wherein, the unit of T1 is percent,
the light-shielding film has an optical density OD of 3 or more with respect to the light of the representative wavelength,
the transfer pattern has:
a main pattern having a diameter W1 and including a light-transmitting portion exposing the transparent substrate;
an auxiliary pattern which is arranged in the vicinity of the main pattern, is composed of a semi-transparent portion in which the semi-transparent film is formed on the transparent substrate, and has a width d; and
a light shielding portion which is disposed in a region of the transfer pattern other than a region where the main pattern and the auxiliary pattern are formed, and in which at least the light shielding film is formed on the transparent substrate,
the auxiliary pattern has a shape of a regular polygonal band or a circular band, and surrounds the circumference of the main pattern,
wherein, when the units of W1 and d are μm,
satisfying the following formulas (1-1), (2) and (5),
0.8≤W1≤3.0 ···(1-1)
30≤T1≤80 ···(5)。
2. the photomask of claim 1,
the width d of the auxiliary pattern satisfies d ≦ W1.
3. The photomask of claim 1 or 2,
the transfer pattern forms a hole pattern having a diameter W2 on the transferred object corresponding to the main pattern, wherein W1 > W2.
4. The photomask of claim 3,
when the difference between the diameter W1 of the main pattern and the diameter W2 on the transferred body, namely W1-W2, is set to offset beta, where beta is in units of μm, 0.2 ≦ beta ≦ 1.0.
5. The photomask of claim 1 or 2,
the light-transmitting portion exposes the transparent substrate,
the semi-light transmitting portion is formed by forming the semi-light transmitting film on the transparent substrate,
the light shielding portion is formed by laminating the semi-light transmissive film and the light shielding film on the transparent substrate.
6. The photomask of claim 1 or 2,
the semi-transparent film is made of a material containing Si and one of Zr, Nb, Hf, Ta, Mo and Ti, or a material containing an oxide, nitride, oxynitride, carbide or oxycarbonitride of the above-mentioned material.
7. The photomask of claim 1,
when the distance between the center of the main pattern and the center of the auxiliary pattern in the width direction is P, wherein the unit of P is mum,
satisfies the following formula (6),
1.0<P≤5.0 ···(6)。
8. the photomask of claim 1 or 2,
the depth of focus is enlarged.
9. A method for manufacturing a photomask for manufacturing a display device, the photomask including a transfer pattern formed on a transparent substrate and used for forming an isolated hole pattern on a transferred object by exposure using an exposure device having an optical system with a numerical aperture NA of 0.08 to 0.20,
the method for manufacturing a photomask is characterized by comprising the following steps:
preparing a photomask blank in which a semi-light-transmitting film and a light-shielding film are laminated on the transparent substrate and a first photoresist film is formed;
a step of forming a first resist pattern by performing first drawing based on the predetermined transfer pattern on the first photoresist film and developing the first resist film;
a step of forming a light shielding film pattern by wet etching the light shielding film using the first resist pattern as a mask;
removing the first resist pattern and forming a second photoresist film on the entire surface including the light shielding film pattern;
performing a second drawing on the second photoresist film and forming a second resist pattern by developing; and
a step of performing wet etching on the semi-light transmissive film using the second resist pattern and the light shielding film pattern as a mask,
the semi-light-transmitting film shifts light of a representative wavelength of exposure light including i-line, h-line, or g-line by 150 to 210 degrees and has a transmittance T1 with respect to the representative wavelength,
wherein, the unit of T1 is percent,
the light-shielding film has an optical density OD of 3 or more with respect to the light of the representative wavelength,
the transfer pattern has:
a main pattern having a diameter W1 and including a light-transmitting portion exposing the transparent substrate;
an auxiliary pattern which is arranged in the vicinity of the main pattern, is composed of a semi-transparent portion in which the semi-transparent film is formed on the transparent substrate, and has a width d; and
a light shielding portion which is disposed in a region of the transfer pattern other than a region where the main pattern and the auxiliary pattern are formed, and in which at least the light shielding film is formed on the transparent substrate,
the auxiliary pattern has a shape of a regular polygonal band or a circular band, and surrounds the circumference of the main pattern,
wherein, when the units of W1 and d are μm,
satisfying the following formulas (1-1), (2) and (5),
0.8≤W1≤3.0 ···(1-1)
30≤T1≤80 ···(5)。
10. the method of manufacturing a photomask according to claim 9,
when the distance between the center of the main pattern and the center of the auxiliary pattern in the width direction is P, wherein the unit of P is mum,
satisfies the following formula (6),
1.0<P≤5.0 ···(6)。
11. a method of manufacturing a display device, comprising:
a step of preparing the photomask according to claim 1 or 2; and
a step of forming a hole pattern having a diameter W2 on the object to be transferred by exposing the transfer pattern to light using an exposure device having a numerical aperture NA of 0.08 to 0.20 and including an exposure light source of i-line, h-line or g-line,
wherein, when the unit of W2 is μm, W2 is in the range of 0.6 μm to 3.0. mu.m.
12. The method for manufacturing a display device according to claim 11,
the exposure using the photomask expands a depth of focus.
13. The method for manufacturing a display device according to claim 11,
the exposure using the photomask reduces a mask error enhancement factor.
Technical Field
The present invention relates to a photomask blank, a photomask, a method for manufacturing a photomask, and a method for manufacturing a display device using the photomask, which are effectively used for manufacturing a display device typified by a liquid crystal or an organic EL.
Background
Patent document 1 describes, as a photomask used for manufacturing a semiconductor device, a phase shift mask in which 4 auxiliary light transmission portions are arranged parallel to each side of a main light transmission portion (hole pattern), and the phases of light in the main light transmission portion and the auxiliary light transmission portions are reversed.
Patent document 2 describes a large phase shift mask including a transparent substrate and a translucent phase shift film formed on the transparent substrate.
Patent document 1: japanese laid-open patent publication No. 3-15845
Patent document 2: japanese patent laid-open publication No. 2013-148892
Currently, in display devices including liquid crystal display devices, EL display devices, and the like, it is desired to be brighter and power-saving, and to improve display performance such as high definition, high-speed display, wide viewing angle, and the like.
For example, in the case of a Thin Film Transistor ("TFT") used in the display device, if a contact hole formed in an interlayer insulating Film does not have a function of reliably connecting patterns of an upper layer and a lower layer among a plurality of patterns constituting the TFT, accurate operation cannot be ensured. On the other hand, in order to increase the aperture ratio of the display device as much as possible to provide a bright and power-saving display device, the diameter of the contact hole needs to be sufficiently small. Accordingly, it is desired that the diameter of the hole pattern provided in the photomask for forming such a contact hole is also reduced (e.g., less than 3 μm). For example, a hole pattern having a diameter of 2.5 μm or less, and further 2.0 μm or less is required, and in the recent years, it is considered that a pattern having a diameter of 1.5 μm or less lower than 2.0 μm is desired to be formed. In light of such a background, a manufacturing technique of a display device capable of reliably transferring a minute contact hole is required.
However, in the field of photomasks for manufacturing semiconductor devices (LSI) having a higher degree of integration and a significantly smaller pattern than those of display devices, in order to obtain a higher resolution, an optical system having a high NA (Numerical Aperture) (for example, 0.2 or more) is applied to an exposure apparatus, and as the exposure light has been reduced in wavelength, excimer lasers of KrF and ArF (each having a single wavelength of 248nm and 193 nm) have been used in many cases.
On the other hand, in the field of photolithography for manufacturing a display device, the above-described method is not generally applied in order to improve resolution. An NA of an exposure apparatus known as an LCD or the like is about 0.08 to 0.10, and a wide wavelength region including an i-line, an h-line, and a g-line is used as an exposure light source, so that production efficiency and cost tend to be rather important than resolution and depth of focus.
However, even in the production of the display device as described above, the demand for miniaturization of the pattern has been unprecedentedly high. Here, there are several problems in using the technology for manufacturing a semiconductor device for manufacturing a display device as it is. For example, conversion to an exposure apparatus with high resolution having a high NA (numerical aperture) requires a large investment, and cannot be matched with the price of a display apparatus. Alternatively, it is difficult to apply the present invention to a display device having a large area by changing the exposure wavelength (the short wavelength such as ArF excimer laser is used with a single wavelength), and even if the present invention is applied, the present invention is not suitable in terms of the need for a large amount of investment in addition to the reduction of the production efficiency.
Further, the photomask for a display device has various problems different from those of the photomask for manufacturing a semiconductor device, such as manufacturing constraints and peculiar problems, as will be described later.
In view of the above situation, it is practically difficult to transfer the photomask of document 1 to a display device. The halftone-type phase shift mask described in document 2 is described to improve the light intensity distribution as compared with a binary mask, but there is still room for improvement in performance.
Disclosure of Invention
Therefore, in a method for manufacturing a display device using a mask for manufacturing a display device, it is desired to overcome the above-described problems and stably transfer a fine pattern to a transfer target. Accordingly, an object of the present invention is to obtain an excellent photomask which is favorably suitable for an exposure environment of a mask for manufacturing a display device and which can stably transfer a minute pattern, and a method for manufacturing the photomask.
In order to solve the above problems, the present invention has the following configurations. The present invention is a photomask characterized by the following structures 1 to 9, a method for manufacturing a photomask characterized by the following structure 10, a method for manufacturing a display device characterized by the following structure 11, and a photomask blank for manufacturing a display device characterized by the following structures 12 and 13.
(Structure 1)
The structure 1 of the present invention is a photomask having a transfer pattern formed by patterning a semi-transparent film and a low-transparent film formed on a transparent substrate, respectively, wherein the semi-transparent film shifts light having a representative wavelength in a wavelength range from i-line to g-line by substantially 180 degrees and has a transmittance T1 (%) with respect to the representative wavelength, and the low-transparent film has a transmittance T2 (%) lower than the transmittance T1 (%) with respect to the light having the representative wavelength, and the transfer pattern has: a main pattern having a diameter W1(μm) and including a light-transmitting portion exposing the transparent substrate; an auxiliary pattern having a width d (μm) and disposed in the vicinity of the main pattern and including a semi-transmissive portion having the semi-transmissive film formed on the transparent substrate; and a low light-transmitting portion which is disposed in a region of the transfer pattern other than the region where the main pattern and the auxiliary pattern are formed and in which at least the low light-transmitting film is formed on the transparent substrate, and which satisfies the following formulas (1) and (2),
0.8≤W1≤4.0...(1)
(Structure 2)
According to the photomask of structure 1, the structure 2 of the present invention is characterized in that the width d of the auxiliary pattern satisfies d ≦ W1.
(Structure 3)
According to the photomask described in the structure 1 or 2, the structure 3 of the present invention is characterized in that the diameter W1 of the main pattern in the transfer pattern is 4.0(μm) or less, and a hole pattern having a diameter W2 (W1 > W2, among others) is formed on the object to be transferred in correspondence with the main pattern.
(Structure 4)
The photomask according to any of structures 1 to 3, wherein structure 4 of the present invention is characterized in that the diameter W1 of the main pattern in the transfer pattern is 4.0(μm) or less, and a hole pattern having a diameter W2 of 3.0(μm) or less (W1 > W2) is formed in the transferred object in correspondence with the main pattern.
(Structure 5)
According to the photomask described in the structure 3 or 4, the structure 5 of the present invention is characterized in that when a difference W1-W2 between the diameter W1 of the main pattern and the diameter W2 of the transferred body is offset β (μm), 0.2. ltoreq. β.ltoreq.1.0.
(Structure 6)
The photomask according to any one of structures 1 to 5, wherein structure 6 of the present invention is characterized in that the transmittance T2 (%) of the low-light-transmitting film with respect to the light having the representative wavelength satisfies T2 < 30.
(Structure 7)
The photomask according to any of structures 1 to 6, wherein the low-light-transmission film substantially does not transmit light of the representative wavelength.
(Structure 8)
According to the photomask of any one of structures 1 to 7, in the structure 8 of the present invention, the translucent portion exposes the transparent substrate, the semi-translucent portion has the semi-translucent film formed on the transparent substrate, and the low translucent portion is formed by laminating the semi-translucent film and the low translucent film on the transparent substrate.
(Structure 9)
The photomask according to any of structures 1 to 8, wherein the semi-transparent film is made of a material containing Si and one of Zr, Nb, Hf, Ta, Mo and Ti, or a material containing an oxide, nitride, oxynitride, carbide or oxycarbonitride of the above material.
(Structure 10)
The structure 10 of the present invention is a method for manufacturing a photomask including a transfer pattern formed on a transparent substrate and used for forming an isolated hole pattern on a transferred object, the method comprising: preparing a photomask blank in which a semi-transparent film and a low-transparent film are laminated on the transparent substrate and a first photoresist film is formed thereon; a step of forming a first resist pattern by performing first drawing based on the predetermined transfer pattern on the first photoresist film and developing the first resist film; forming a low light transmission film pattern by wet etching the low light transmission film using the first resist pattern as a mask; removing the first resist pattern and forming a second photoresist film over the entire surface including the low-transmittance film pattern; performing a second drawing on the second photoresist film and forming a second resist pattern by developing; and wet etching the semi-transparent film using the second resist pattern and the low-light-transmittance film pattern as a mask, wherein the semi-transparent film shifts light having a representative wavelength in a wavelength range from i-line to g-line by substantially 180 degrees and has a transmittance T1 (%) with respect to the representative wavelength, and the low-light-transmittance film has a transmittance T2 (%) with respect to the light having the representative wavelength, which is lower than the transmittance T1 (%) of the semi-transparent film, and the transfer pattern has: a main pattern having a diameter W1(μm) and including a light-transmitting portion exposing the transparent substrate; an auxiliary pattern having a width d (μm) and disposed in the vicinity of the main pattern and including a semi-transmissive portion having the semi-transmissive film formed on the transparent substrate; and a low light-transmitting portion which is disposed in a region of the transfer pattern other than the region where the main pattern and the auxiliary pattern are formed and in which at least the low light-transmitting film is formed on the transparent substrate, satisfy the following formulas (1) and (2),
0.8≤W1≤4.0…(1)
(Structure 11)
The structure 11 of the present invention is a method of manufacturing a display device, including: a step of preparing a photomask according to any one of structures 1 to 9; and a step of forming a hole pattern having a diameter W2 of 0.6 to 3.0(μm) on the object to be transferred by exposing the transfer pattern using an exposure device having a Numerical Aperture (NA) of 0.08 to 0.20 and including an exposure light source of i-line, h-line, and g-line.
(Structure 12)
The structure 12 of the present invention is a photomask blank for manufacturing a display device, in which a semi-transparent film having a transmittance T1 of 30 to 80 (%) for a representative wavelength in a wavelength range from an i line to a g line and a low-transparent film having a transmittance smaller than that of the semi-transparent film for the representative wavelength are laminated on the transparent substrate, wherein the semi-transparent film has a refractive index of 1.5 to 2.9 for the representative wavelength and is formed in a film thickness having a phase shift amount of substantially 180 degrees, and the low-transparent film does not substantially transmit light of the representative wavelength or has a transmittance of less than 30% and a phase shift amount of substantially 180 degrees.
(Structure 13)
According to the photomask blank for manufacturing a display device described in structure 12, structure 13 of the present invention is characterized in that the semi-transparent film can be made of a transition metal containing Zr, Nb, Hf, Ta, Mo, or Ti, a material containing Si, or a material containing an oxide, nitride, oxynitride, carbide, or oxycarbonitride thereof.
According to the present invention, an excellent photomask which is favorably suitable for an exposure environment of a mask for manufacturing a display device and which can stably transfer a minute pattern, and a method for manufacturing the photomask can be provided.
Drawings
Fig. 1 (a) is a schematic top view and (b) is a schematic cross-sectional view of an example of a photomask of the present invention.
In fig. 2, (a) to (f) are schematic plan views of other examples of the photomask of the present invention.
Fig. 3 is a schematic sectional view and a schematic plan view showing an example of a process for manufacturing a photomask according to the present invention.
FIG. 4 is a schematic plan view of photomasks of comparative examples 1-1 and 1-2 and example 1, showing dimensions and transfer performance based on optical simulation.
Fig. 5 shows the case where the photomasks of comparative examples 1-1 and 1-2 and example 1 were used, in which (a) is an aerial image showing the intensity of light formed on the transfer object in this case, and (b)25 is a view showing the cross-sectional shape of the resist pattern formed thereby.
FIG. 6 is a schematic plan view of photomasks of comparative examples 2-1 and 2-2 and example 2, showing dimensions and transfer performance based on optical simulation.
Fig. 7 shows the case where the photomasks of comparative examples 2-1 and 2-2 and example 2 were used, in which (a) is an aerial image showing the intensity of light formed on the transfer object in this case, and (b) is a view showing the cross-sectional shape of the resist pattern formed thereby.
Detailed Description
When the CD (Critical Dimension, hereinafter, used in the meaning of pattern line width) of a transfer pattern of a photomask is miniaturized, it becomes more difficult to perform a step of accurately transferring the pattern to a transfer target (a thin film to be etched, or the like, also referred to as a target). The resolution limit of an exposure apparatus for a display device, which is specified by the specification, is usually about 2 μm to 3 μm. In contrast, in the transfer pattern to be formed, a pattern having a size close to or lower than the size has appeared. Further, since the mask for manufacturing a display device has a larger area than the mask for manufacturing a semiconductor device, it is difficult to uniformly transfer a transfer pattern having a CD of less than 3 μm in a plane in actual production.
Therefore, it is necessary to develop the transfer performance effectively by devising factors other than the pure resolution (which depends on the exposure wavelength and the numerical aperture of the exposure optical system).
Further, since the area of the transfer target (flat panel display substrate) is large, it can be said that an environment in which defocusing due to the surface flatness of the transfer target is likely to occur in the process of pattern transfer by exposure. In this environment, it makes a significant sense to sufficiently ensure the Depth of field (DOF) of the Focus at the time of exposure.
Further, a photomask for manufacturing a display device is large in size as is well known, and it is not easy to ensure CD uniformity at all positions in a plane in wet processing (development, wet etching) in a photomask manufacturing process. Even if the final CD accuracy is within a predetermined allowable range, it is important to ensure a sufficient depth of focus (DOF) in the exposure process, and it is desirable that other performances are not deteriorated.
The present invention provides a photomask having a transfer pattern formed by patterning a semi-transparent film and a low-transparent film formed on a transparent substrate. FIG. 1 shows an example of a transfer pattern having a photomask according to the present invention. In fig. 1, (a) is a schematic plan view and (b) is a schematic sectional view.
As shown in fig. 1 (a), the transfer pattern formed on the transparent substrate includes a main pattern and an auxiliary pattern disposed in the vicinity of the main pattern.
In this embodiment, the main pattern is formed of a translucent portion exposing the transparent substrate, and the auxiliary pattern is formed of a translucent portion having a translucent film formed on the transparent substrate. The portion surrounding the main pattern and the auxiliary pattern is a low light transmission portion in which at least a low light transmission film is formed on the transparent substrate. That is, in the transfer pattern shown in fig. 1, the region other than the region where the main pattern and the auxiliary pattern are formed is a low light transmission portion. In this embodiment, as shown in fig. 1 (b), the semi-transparent film and the low-transparent film are laminated on the transparent substrate in the low-transparent portion. The semi-light-transmitting film has a phase shift amount that substantially shifts light of a representative wavelength in a wavelength range from i-line to g-line by 180 degrees, and has a transmittance T1 (%) with respect to the representative wavelength.
The low-light-transmission film of the photomask of the present invention is a film having a predetermined low transmittance with respect to a representative wavelength of exposure light. The low-light-transmission film used for manufacturing the photomask of the present invention can have a transmittance T2 (%) lower than the transmittance T1 (%) of the semi-light-transmitting film with respect to light having a representative wavelength in the wavelength range from the i-line to the g-line.
Here, when the diameter (W1) of the main pattern is 4 μm or less, a minute main pattern (hole pattern) having a diameter W2(μm) (where W1 > W2) can be formed on the transferred object in correspondence with the main pattern.
Specifically, W1(μm) is preferably in the relationship shown in the following formula (1).
0.8≤W1≤4.0…(1)
The diameter W2(μm) of the main pattern (hole pattern) formed on the transferred body at this time can be 0.6. ltoreq. W2. ltoreq.3.0.
In addition, the photomask of the present invention can be used for the purpose of forming a pattern of a minute size useful for manufacturing a display device. For example, when the diameter W1 of the main pattern is 3.0(μm) or less, the effect of the present invention is more remarkable. The diameter W1(μm) of the main pattern can be preferably set to 1.0. ltoreq. W1. ltoreq.3.0. Further, the relationship between the diameter W1 and the diameter W2 may be W1 — W2, but W1 > W2 is preferable. That is, when β (μm) is set to the offset value, 0.2 β ≦ 1.0, and more preferably 0.2 β ≦ 0.8 when β ≦ W1-W2 > 0(μm). Thus, as will be described later, advantageous effects such as reduction in loss of the resist pattern on the transfer target can be obtained.
In the above, the diameter W1 of the main pattern means the diameter of a circle or a value approximate thereto. For example, when the shape of the main pattern is a regular polygon, the diameter W1 of the main pattern is the diameter of an inscribed circle. If the shape of the main pattern is a square as shown in fig. 1, the diameter W1 of the main pattern is the length of one side. The diameter W2 of the main pattern after transfer is the same as the diameter of a circle or a value similar thereto.
Needless to say, when a finer pattern is to be formed, W1 can be set to 2.5(μm) or less, or 2.0(μm) or less, and W1 can be set to 1.5(μm) or less.
The phase difference between the main pattern and the auxiliary pattern with respect to the representative wavelength of the exposure light used for exposing the photomask of the present invention having the transfer patternApproximately 180 degrees. That is, the phase difference between the light of the representative wavelength transmitted through the main pattern and the light of the representative wavelength transmitted through the auxiliary pattern
The photomask of the present invention is remarkably effective when exposure light including i-line, h-line, or g-line is used, and is particularly suitable for use in exposure light having a wide wavelength including i-line, h-line, and g-line. In this case, the representative wavelength may be any of an i-line, an h-line, and a g-line. For example, the photomask of the present invention can be configured with the h-line as a representative wavelength.
In order to form such a retardation, the main pattern may be a translucent portion in which the main surface of the transparent substrate is exposed, the auxiliary pattern may be a semi-translucent portion in which a semi-translucent film is formed on the transparent substrate, and a phase shift amount of the semi-translucent film with respect to the representative wavelength may be set to approximately 180 degrees.
The transmittance T1 of the semi-light-transmitting portion can be set as follows. That is, when the transmittance of the semi-transmissive film formed in the semi-transmissive section with respect to the above representative wavelength is T1 (%), T1 is 30. ltoreq. T1. ltoreq.80. More preferably 40. ltoreq. T1. ltoreq.75. The transmittance T1 (%) is the transmittance at the above representative wavelength with respect to the transmittance of the transparent substrate.
In the photomask of the present invention, the low light transmission portion that is disposed in the region other than the region where the main pattern and the auxiliary pattern are formed and that is formed so as to surround the main pattern and the auxiliary pattern may be configured as follows.
The low light transmission portion is a low light transmission film (i.e., a light shielding film) which is substantially impermeable to exposure light (light having a representative wavelength in the wavelength range of i-g line), and may be a film formed by forming a film having an optical concentration OD of 2 or more (preferably OD of 3 or more, more preferably OD of 5 or more) on a transparent substrate.
Alternatively, the low light transmission portion may be formed by forming a low light transmission film that transmits exposure light within a predetermined range. In the case where the exposure light is transmitted within a predetermined range, the transmittance T3 (%) of the low light-transmitting portion (here, the transmittance of the stack in the case where the semi-light-transmitting film and the low light-transmitting film are stacked) satisfies 0 < T3 < T1. Preferably, 0 < T3 ≦ 20 is satisfied. The transmittance T3 (%) is a transmittance at the above representative wavelength with reference to the transmittance of the transparent substrate.
In the case where the low-light-transmission film transmits the exposure light at a predetermined transmittance, the phase difference between the transmitted light of the low-light-transmission portion and the transmitted light of the light-transmission portion is preferably set
The low-light-transmitting film used for the photomask of the present invention is preferably substantially opaque to the light of the above-mentioned representative wavelength, or has a transmittance (T2 (%) (i.e., 0 < T2 < 30)) of less than 30 (%) and a phase shift amount
The transmittance here is also, as described above, the transmittance of the representative wavelength with reference to the transmittance of the transparent substrate.
When the width of the auxiliary pattern in the transfer pattern is d (μm), the excellent effect of the present invention can be obtained when the following formula (2) is satisfied between the width d of the auxiliary pattern and the light transmittance T1 in that portion.
Here, the first and second liquid crystal display panels are,is a factor (hereinafter, simply referred to as a factor) indicating the amount of light transmitted through the auxiliary pattern. The formula (2) represents an appropriate range of the factor, and when the factor is larger than 1.5, the loss of the thickness of the slit (slit) portion of the resist layer becomes larger beyond an allowable range as shown in fig. 5 (b), and when the factor is larger than 0.5, sufficient resolution cannot be obtained. In this case, the distance between the center of the main pattern and the center of the auxiliary pattern in the width direction is defined as a pitch P (μm), and the pitch P preferably satisfies a relationship of 1.0 < P.ltoreq.5.0. More preferably, the pitch P is 1.5 < + >P≤4.5。
In the present invention, the auxiliary Pattern has an effect of assuming an optical function such as a Dense Pattern (Dense Pattern) to the main Pattern independent of the design, but when the above relational expression is satisfied, exposure light having passed through the main Pattern and the auxiliary Pattern mutually interacts well, and excellent transfer performance as shown in examples described later can be exhibited.
The width d (. mu.m) of the auxiliary pattern is a dimension (e.g., d.ltoreq.3.0, preferably d.ltoreq.2.5) of a resolution limit or less under the exposure conditions (exposure apparatus used) applied to the photomask of the present invention, and is specifically exemplified by d.gtoreq.0.7, more preferably d.gtoreq.0.8. Furthermore, d.ltoreq.W 1 is preferred, and d.ltoreq.W 1 is more preferred.
More preferably, the relational expression (2) is the following expression (2) -1, and still more preferably the following expression (2) -2.
As described above, the main pattern of the photomask shown in fig. 1 is a square, but the present invention is not limited thereto. For example, as shown by way of example in fig. 2, the main pattern of the photomask can have a rotationally symmetric shape including an octagon or a circle. The center of rotational symmetry can be set as the center of the reference of P.
The shape of the auxiliary pattern of the photomask shown in fig. 1 is an octagonal stripe, but the present invention is not limited thereto. The shape of the auxiliary pattern is preferably a shape in which a certain width is given to the shape of the rotation target that is symmetrical 3 times or more with respect to the center of the hole pattern. The shapes of the main pattern and the auxiliary pattern are preferably those illustrated in fig. 2 (a) to (f), and the design of the main pattern and the design of the auxiliary pattern may be combined with each other by different patterns illustrated in fig. 2 (a) to (f).
For example, the outer periphery of the auxiliary pattern is a regular polygon (preferably a regular 2 n-sided polygon, where n is an integer of 2 or more) such as a square, a regular hexagon, a regular octagon, or a regular decagon, or a circle. Further, as the shape of the auxiliary pattern, a shape in which the outer periphery and the inner periphery of the auxiliary pattern are substantially parallel, that is: preferably in the shape of a regular polygon or circular strip having a substantially constant width. The strip-like shape is also referred to as a polygonal strip or a circular strip. As the shape of the auxiliary pattern, such a regular polygonal band or a circular band is preferably a shape surrounding the periphery of the main pattern. In this case, the balance between the amounts of light transmitted through the main pattern and the auxiliary pattern can be made substantially equal, and therefore, the interaction of light for obtaining the effect of the present invention can be easily obtained.
In particular, when the photomask of the present invention is used as a photomask for manufacturing a display device, the photomask of the present invention includes: when the photomask of the present invention is used in combination with a photoresist layer for manufacturing a display device, the resist loss in the portion of the transferred object corresponding to the auxiliary pattern can be reduced.
Alternatively, the auxiliary pattern may have a shape that does not completely surround the main pattern, but the polygonal band or the circular band may be partially missing. The shape of the auxiliary pattern may be a shape lacking the corners of the square band, as shown in fig. 2 (f), for example.
In addition, other patterns than the main pattern and the auxiliary pattern of the present invention may be used as long as the effects of the present invention are not affected.
An example of the method for manufacturing a photomask according to the present invention will be described below with reference to fig. 3.
As shown in fig. 3 (a), a photomask blank is prepared.
The photomask blank is formed by sequentially forming a semi-transparent film and a low-transparent film on a transparent substrate made of glass or the like, and is coated with a first photoresist film.
The semi-transparent film is as follows: the main surface of the transparent substrate has a transmittance of 30 to 80 (%) (30. ltoreq. T1. ltoreq.80, when T1 (%) is the transmittance), more preferably 40 to 75 (%), when any of i-line, h-line, and g-line is a representative wavelength, and the amount of phase shift with respect to the representative wavelength is substantially 180 degrees. With such a semi-transmissive film, the phase difference of transmitted light between the main pattern formed of the light-transmissive portion and the auxiliary pattern formed of the semi-transmissive portion can be made substantially 180 degrees. Such a semi-transparent film shifts the phase of light having a representative wavelength in the wavelength range from i-line to g-line by approximately 180 degrees. As a method for forming the semi-transparent film, a known method such as a sputtering method can be used.
The semi-transmissive film preferably satisfies the above transmittance and retardation, and is made of a material that can be wet-etched as described below. Among them, the range of the film thickness is preferable because if the amount of side etching generated during wet etching is too large, problems such as deterioration of CD accuracy and breakage of the upper layer film due to undercut (undercut) occur, and the like
In order to satisfy the above conditions, the refractive index of the light for exposure of the semi-permeable film material at a representative wavelength (e.g., h-line) is preferably 1.5 to 2.9. More preferably 1.8 to 2.4.
In order to sufficiently exhibit the phase shift effect, it is preferable that the pattern profile (etched surface) by wet etching is vertically close to the main surface of the transparent substrate.
In consideration of the above properties, the film material of the semi-transparent film may be made of a material containing Si and any one of Zr, Nb, Hf, Ta, Mo, and Ti, or a material containing an oxide, nitride, oxynitride, carbide, or oxycarbonitride of the above materials.
A low transmittance film is formed on a semi-transmittance film of a photomask blank. As the film formation method, a known method such as a sputtering method can be applied as in the case of the semi-transparent film.
The low transmission film of the photomask blank is substantially opaque to the exposure light. Or may be a film having a predetermined low transmittance with respect to the representative wavelength of the exposure light. The low-light-transmission film used for manufacturing the photomask of the present invention has a transmittance T2 (%) lower than the transmittance T1 (%) of the semi-light-transmitting film with respect to light having a representative wavelength in the wavelength range from the i-line to the g-line.
In the case where the low-light-transmitting film is capable of transmitting exposure light, it is desirable that the transmittance and the phase shift amount of the low-light-transmitting film with respect to the exposure light can achieve the transmittance and the phase shift amount of the low-light-transmitting portion of the photomask of the present invention. Preferably, the film has a transmittance T3 (%) of T3 ≦ 20 with respect to the light having the representative wavelength of the exposure light in a laminated state of the low-light-transmission film and the semi-light-transmission film, and has a phase shift amountIs 90 degrees or less, and more preferably 60 degrees or less.
As the property of the low-light-transmitting film alone, it is preferable that the film does not substantially transmit light of the above-mentioned representative wavelength, or has a transmittance (T2 (%)) (i.e., 0 < T2 < 30) of less than 30 (%), and a phase shift amount
The material of the low light-transmitting film of the photomask blank may be Cr or a compound thereof (oxide, nitride, carbide, oxynitride or carbonitrooxyfluoroneon), or a silicide of a metal containing Mo, W, Ta or Ti, or the above-mentioned compound of the silicide. Among them, the material of the low-light-transmission film of the photomask blank is capable of wet etching as well as the semi-light-transmission film, and is preferably a material having etching selectivity with respect to the material of the semi-light-transmission film. That is, the low-light-transmittance film is desired to have resistance to an etchant for the semi-light-transmittance film, and the semi-light-transmittance film is desired to have resistance to an etchant for the low-light-transmittance film.
A first photoresist film is also coated on the low light transmission film of the photomask blank. The photomask of the present invention is preferably drawn by a laser drawing apparatus to form a photoresist layer suitable for the laser drawing apparatus. The first photoresist film may be a positive film or a negative film, and will be described as a positive film.
Next, as shown in fig. 3 (b), drawing (first drawing) based on drawing data of the transfer pattern is performed on the first photoresist film using a drawing device. Then, the low light-transmitting film is wet-etched using the first resist pattern obtained by the development as a mask. This divides the region into the low light transmission portions and the region of the auxiliary pattern (low light transmission film pattern) surrounded by the low light transmission portions. As the etching solution (wet etchant) used for wet etching, a known etching solution having a composition suitable for the low light-transmitting film to be used can be used. For example, in the case of a Cr-containing film, cerium ammonium nitrate or the like can be used as the wet etchant.
Next, as shown in fig. 3 (c), the first resist pattern is peeled off.
Next, as shown in fig. 3 (d), a second photoresist film is applied to the entire surface including the formed low light-transmitting film pattern.
Next, as shown in fig. 3 (e), the second photoresist film is subjected to second drawing, and a second resist pattern formed by development is formed. The second resist pattern and the low-transmittance film pattern are used as masks to perform wet etching of the semi-transmittance film. By this etching (development), a region of the main pattern is formed in which the light-transmitting portion of the transparent substrate is exposed. The second resist pattern is preferably a pattern having an opening in a region to be the main pattern formed of the light-transmitting portion, covering a region to be the auxiliary pattern, and the second resist pattern is preferably applied with respect to the second drawing data so that an edge of the low light-transmitting film is exposed from the opening. Thus, the misalignment caused between the first drawing and the second drawing can be absorbed, and the CD accuracy of the transfer pattern can be prevented from being deteriorated.
That is, by applying the second resist pattern during the second drawing in this manner, when the independent hole pattern is to be formed on the object to be transferred, since the light-shielding film and the semi-light-transmitting film are patterned without positional deviation, the centers of gravity of the main pattern and the auxiliary pattern can be accurately matched in the transfer pattern illustrated in fig. 1.
The wet etchant for the semi-transparent film is appropriately selected depending on the composition of the semi-transparent film.
Next, as shown in fig. 3 (f), the second resist pattern is peeled off to complete the photomask of the present invention shown in fig. 1.
In the production of a photomask for a display device, when an optical film such as a light-shielding film formed on a transparent substrate is patterned, dry etching and wet etching are used as suitable etching. Either may be used, but wet etching is particularly advantageous in the present invention. This is because the size of a photomask for a display device is relatively large and there are various sizes. When dry etching using a vacuum chamber is applied to manufacture such a photomask, efficiency is reduced in the size of the dry etching apparatus and in the manufacturing process.
Among them, there is a problem associated with the application of wet etching in the production of such a photomask. Since wet etching has isotropic etching properties, when a predetermined film is etched in the depth direction and eluted, etching is also performed in a direction perpendicular to the depth direction. For example, when a slit is formed by etching a semi-transparent film having a film thickness of f (nm), the opening of the resist pattern serving as an etching mask is smaller by 2f (nm) (i.e., smaller by f (nm) on one side) than a desired slit width, but it is more difficult to maintain the dimensional accuracy of the opening of the resist pattern with a slit having a smaller width. Therefore, it is useful that the width d of the auxiliary pattern is 1 μm or more, preferably 1.3 μm or more.
In addition, when the film thickness f (nm) is large, since the amount of side etching is also large, even if the film thickness is small, it is advantageous to use a film material having a phase shift amount of approximately 180 degrees, and as a result, it is desirable that the refractive index of the semi-transmissive film with respect to the wavelength is high. Therefore, a material having a refractive index of 1.5 to 2.9, preferably 1.8 to 2.4, and preferably a semi-transparent film is used for the representative wavelength.
The present invention includes a method for manufacturing a display device, which includes a step of exposing the photomask of the present invention to light with an exposure device to transfer the transfer pattern to a transfer target.
In the method for manufacturing a display device of the present invention, the photomask of the present invention is prepared. Then, the transfer pattern is exposed using an exposure apparatus having a Numerical Aperture (NA) of 0.08 to 0.20 and having an exposure light source including i-line, h-line, and g-line, and a hole pattern having a diameter W2 of 0.6 to 3.0 μm is formed on the transfer object. The exposure is generally performed by an exposure of an equal magnification, which is advantageous.
The photomask of the present invention is used as an exposure apparatus for performing an equal-magnification projection exposure, which is a system for transferring a transfer pattern using the photomask of the present invention. That is, the exposure apparatus used for LCD (or FPD, liquid crystal) is configured such that the Numerical Aperture (NA) of the optical system is 0.08 to 0.15 (coherence factor (σ) is 0.4 to 0.9), and the exposure apparatus includes a light source (also referred to as a wide wavelength source) for exposure light including at least one of i-line, h-line, and g-line. Of course, the present invention can be applied to an exposure apparatus having a numerical aperture NA of 0.10 to 0.20, and the effects of the present invention can be obtained.
In addition, although the light source of the exposure apparatus used may be deformed illumination (ring-shaped illumination or the like), the excellent effects of the present invention can be obtained even by non-deformed illumination.
The present invention includes photomask blanks for use in making the photomasks of the present invention described above. Specifically, the photomask blank of the present invention has a semi-light-transmissive film and a low-light-transmissive film laminated on a transparent substrate. And may also be coated with a resist film.
The physical properties, film quality, and composition of the semi-transparent film and the low-transparent film are as described above.
That is, the transmittance T1 of the semi-transparent film of the photomask blank of the present invention is 30 to 80 (%) with respect to a representative wavelength in the wavelength range from i-line to g-line. The semi-transparent film has a refractive index of 1.5 to 2.9 with respect to the representative wavelength and has a thickness of a phase shift amount of approximately 180 degrees. The semi-transparent film having such a refractive index has a desired phase shift amount even when the film thickness is sufficiently thin, and the wet etching time of the semi-transparent film can be shortened. As a result, side etching of the semi-transparent film can be suppressed.
The low-light-transmission film of the photomask blank of the present invention has a transmittance lower than that of the semi-light-transmission film for the representative wavelength. The low-light-transmitting film substantially does not transmit light of the representative wavelength, or has a transmittance of less than 30% and a phase shift amount of substantially 180 degrees.
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