JP2020122988A - Photomask and manufacturing method of display device - Google Patents

Abstract

To provide an excellent photomask which is advantageously adapted to an exposure environment of a mask for manufacturing a display device and in which a fine pattern can be stably transferred, and a manufacturing method thereof.SOLUTION: A photomask comprises a pattern for transfer which is formed on a transparent substrate, in which the pattern for transfer has: a main pattern having a diameter W1(μm); an auxiliary pattern having a width d(μm) which is arranged in the vicinity of the main pattern; and a low light-transmitting part which is arranged in a region other than an area where the main pattern and the auxiliary pattern are formed, a phase difference between the representative wavelengths transmitting through the main pattern and the auxiliary pattern is approximately 180 degrees, the diameter W1, the width d, transmittance T1(%) of the auxiliary pattern, transmittance T3(%) of the low light-transmitting part, and a distance P(μm) between the center of the main pattern and the center of the auxiliary pattern in a width direction have a predetermined relationship.SELECTED DRAWING: Figure 1

Description

The present invention relates to a photomask typified by liquid crystal and organic EL, which is advantageously used for manufacturing a display device, and a method for manufacturing a display device using the photomask.

In Patent Document 1, as a photomask used for manufacturing a semiconductor device, four auxiliary light-transmitting portions are arranged in parallel to each side of a main light-transmitting portion (hole pattern). There is described a phase shift mask in which the phase of the light of a part is inverted.

Patent Document 2 describes a large phase shift mask having a transparent substrate and a semitransparent phase shift film formed on the transparent substrate.

JP-A-3-15845 JP, 2013-148892, A

At present, in display devices including a liquid crystal display device and an EL display device, it is desired that the display device is brighter and consumes less power, and has improved display performance such as high definition, high speed display, and wide viewing angle.

For example, in the case of a thin film transistor (“TFT”) used in the above display device, the contact holes formed in the interlayer insulating film among the plurality of patterns forming the TFT are sure to be the patterns of the upper and lower layers. The correct operation cannot be guaranteed unless it has a function of connecting. On the other hand, the diameter of the contact hole is required to be sufficiently small in order to maximize the aperture ratio of the display device and make it a bright and power-saving display device. Along with this, it is desired that the diameter of the hole pattern provided in the photomask for forming such a contact hole is also miniaturized (for example, 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 it is considered that formation of a pattern having a diameter of 1.5 μm or less, which is smaller than the hole pattern, is desired in the near future. With such a background, there is a need for a display device manufacturing technique capable of reliably transferring a minute contact hole.

By the way, in the field of photomasks for semiconductor device (LSI) manufacturing, which has a higher degree of integration and a markedly finer pattern than that of a display device, in order to obtain high resolution, an exposure apparatus has a high NA. (For example, 0.2 or more) optical system has been applied to shorten the wavelength of exposure light, and it seems that KrF and ArF excimer lasers (single wavelength of 248 nm and 193 nm, respectively) are often used. Became.

On the other hand, in the field of lithography for manufacturing a display device, it has not been general to apply the above method in order to improve resolution. Rather, the exposure apparatus known for LCD (liquid crystal display) has an NA of about 0.08 to 0.10, and the exposure light source also includes i-line, h-line, and g-line, and has a broad wavelength. By using regions, production efficiency and cost tend to be emphasized rather than resolution and depth of focus.

However, as described above, the demand for pattern miniaturization is higher than ever before in the manufacture of display devices. Here, there are some problems in directly applying the technique for manufacturing a semiconductor device to the manufacture of a display device. For example, a conversion to a high-resolution exposure apparatus having a high NA (numerical aperture) requires a large investment and cannot be matched with the price of a display device. Alternatively, changing the exposure wavelength (using a short wavelength such as ArF excimer laser with a single wavelength) is difficult to apply to a display device having a large area, and if it is applied, production efficiency will be reduced. In addition to decreasing, it is also inconvenient in that it requires considerable investment.

Further, as will be described later, the photomask for the display device has manufacturing restrictions and various unique problems, which are different from those of the photomask for manufacturing the semiconductor device.

From the above circumstances, it is practically difficult to divert the photomask of Patent Document 1 as it is to manufacture a display device. Further, the halftone type phase shift mask described in Patent Document 2 has a description that the light intensity distribution is improved as compared with the binary mask, but there is room for further improvement in performance.

Therefore, in a method of manufacturing a display device using a mask for manufacturing a display device, it has been desired to overcome the above-mentioned problems and to perform stable transfer onto a transfer target with a fine pattern. Therefore, it is an object of the present invention to obtain an excellent photomask which is suitable for the exposure environment of a mask for manufacturing a display device and can stably transfer a fine pattern, and a manufacturing method thereof.

The present invention has the following configuration in order to solve the above problems. The present invention is a method of manufacturing a photomask having the following configurations 1 to 14 and a display device having the following configuration 15.

(Structure 1)
Configuration 1 of the present invention is a photomask including a transfer pattern formed on a transparent substrate, wherein the transfer pattern is arranged in the vicinity of the main pattern having a diameter W1 (μm) and the main pattern. , An auxiliary pattern having a width d (μm), and a low light-transmitting portion arranged in a region other than the main pattern and the auxiliary pattern are formed, and i-line to g-line that transmits the main pattern The phase difference between the representative wavelength in the wavelength range and the representative wavelength that passes through the auxiliary pattern is about 180 degrees, and the transmittance of light of the representative wavelength that passes through the auxiliary pattern is T1 (%). When the transmittance of light of the representative wavelength that passes through the low light-transmitting portion is T3 (%), and the distance between the center of the main pattern and the center of the auxiliary pattern in the width direction is P (μm). And a photomask satisfying the following formulas (1) to (4).
0.8 ≤ W1 ≤ 4.0 (1)

1.0 <P ≤ 5.0 (3)
T3 <T1 (4)

(Configuration 2)
Constitution 2 of the present invention is characterized in that the auxiliary pattern is formed by forming, on the transparent substrate, a semi-transmissive film having a transmittance of T1 (%) for the light of the representative wavelength. It is the described photomask.

(Structure 3)
A third aspect of the present invention is the photomask according to the second aspect, wherein the transmittance T1(%) of the semi-transparent film satisfies the following expression (5).
30 ≤ T1 ≤ 80 (5)

(Structure 4)
Structure 4 of the present invention is the photomask according to Structure 2 or 3, wherein the width d of the auxiliary pattern is 1 (μm) or more.

(Structure 5)
In a fifth aspect of the present invention, the main pattern is formed by exposing a part of a main surface of the transparent substrate, and the auxiliary pattern is formed by forming the semitransparent film on the transparent substrate. In the low light-transmitting portion, the semi-light-transmitting film and the low light-transmitting film having a transmittance of light of the representative wavelength of T2 (%) are provided on the transparent substrate in this order or vice versa. It is a photomask in any one of the structures 2-4 characterized by being laminated|stacked in order.

(Structure 6)
In a sixth aspect of the present invention, the main pattern is formed by engraving the main surface of the transparent substrate, and the auxiliary pattern is formed by forming the semitransparent film on the transparent substrate. In the low light-transmitting portion, the semi-light-transmitting film and the low light-transmitting film having a transmittance of light of the representative wavelength of T2 (%) are provided on the transparent substrate in this order or vice versa. The photomask according to any one of configurations 2 to 4, wherein the photomask is laminated in order.

(Structure 7)
In the seventh aspect of the present invention, the semitransparent film is a material containing at least one of Zr, Nb, Hf, Ta, Mo and Ti and Si, or an oxide, a nitride or an oxynitride of these materials. 7. The photomask according to any one of configurations 2 to 6, which is made of a material containing a substance, a carbide, or an oxynitride carbide.

(Structure 8)
A structure 8 of the present invention is the photomask according to the structure 1, wherein the transparent substrate is exposed in the auxiliary pattern.

(Configuration 9)
According to a ninth aspect of the present invention, the main pattern is formed by engraving the main surface of the transparent substrate, and the auxiliary pattern is formed by exposing a part of the main surface of the transparent substrate, and the low transparency. 9. The photomask according to configuration 8, wherein the light portion is formed of a low light-transmitting film having a transmittance of light of the representative wavelength of T3 (%) on the transparent substrate. Is.

(Structure 10)
In the structure 10 of the present invention, the main pattern is formed by exposing a part of the main surface of the transparent substrate, and the auxiliary pattern is formed by engraving the main surface of the transparent substrate. 9. The photomask according to configuration 8, wherein the light portion is formed of a low light-transmitting film having a transmittance of light of the representative wavelength of T3 (%) on the transparent substrate. Is.

(Configuration 11)
Structure 11 of the present invention is characterized in that a hole pattern having a transfer diameter W2 of 3.0 (μm) or less (where W1>W2) is formed on the transferred body corresponding to the main pattern. The photomask according to any one of Configurations 1 to 10.

(Configuration 12)
Configuration 12 of the present invention is such that, when a difference W1-W2 between the diameter W1 of the main pattern and the transfer diameter W2 on the transfer target is a bias β (μm),
0.2≦β≦1.0 (6)
The photomask according to the eleventh aspect is characterized in that

(Configuration 13)
In the structure 13 of the present invention, the transmittance T3 (%) of the low light-transmitting portion with respect to the light of the representative wavelength is
T3<30...(7)
13. The photomask according to any one of Configurations 1 to 12, which satisfies the above condition.

(Configuration 14)
Structure 14 of the present invention is the photomask according to any one of Structures 1 to 12, wherein the low light-transmitting portion does not substantially transmit light having the representative wavelength.

(Structure 15)
Constitution 15 of the present invention is the step of preparing the photomask according to any one of constitutions 1 to 14, and the numerical aperture (NA) is 0.08 to 0.20. Exposing the transfer pattern using an exposure device having an exposure light source including at least one to form a hole pattern having a diameter W2 of 0.6 to 3.0 (μm) on the transfer target; And a method for manufacturing a display device.

According to the present invention, it is possible to provide an excellent photomask that can be adapted to the exposure environment of a mask for manufacturing a display device and can stably transfer a fine pattern, and a manufacturing method thereof.

It is a plane schematic diagram of an example of the photomask of this invention. It is a plane schematic diagram (a)-(f) of the other example of the photomask of this invention. It is an example (a)-(f) of the layer structure of the photomask of this invention. FIG. 6 is a schematic cross-sectional view and a schematic plan view showing an example of the manufacturing process of the photomask of the present invention. FIG. 3 is a schematic plan view of the photomasks of Comparative Examples 1-1 and 1-2 and Example 1, and dimensions and transfer performance by optical simulation. (A) an aerial image of the light intensity formed on the transferred material when the photomasks of Comparative Examples 1-1 and 1-2 and Example 1 were used, and (b) of the resist pattern formed thereby. It is a figure which shows a cross-sectional shape. FIG. 4 is a schematic plan view of the photomasks of Comparative Examples 2-1 and 2-2 and Example 2, and dimensions and a diagram showing transfer performance by optical simulation. (A) an aerial image of the light intensity formed on the transferred material when the photomasks of Comparative Examples 2-1 and 2-2 and Example 2 were used, and (b) the resist pattern formed thereby. It is a figure which shows a cross-sectional shape.

When the CD (Critical Dimension, hereinafter used to mean the pattern line width) of the transfer pattern of the photomask is miniaturized, this is accurately transferred (also referred to as an object to be processed such as a thin film to be etched). It becomes more difficult to carry out the step of transferring to. In most cases, the resolution limit specified as a specification for an exposure apparatus for a display device is about 2 to 3 μm. On the other hand, some of the transfer patterns to be formed have already come close to or less than this size. Further, since the mask for manufacturing a display device has a larger area than the mask for manufacturing a semiconductor device, in actual production, it is very difficult to uniformly transfer a transfer pattern having a CD of less than 3 μm in a plane.

Therefore, it is necessary to bring out effective transfer performance by devising elements other than pure resolution (depending on the exposure wavelength and the numerical aperture of the exposure optical system).

Further, since the transfer target (flat panel display substrate) has a large area, it can be said that defocusing due to the surface flatness of the transfer target is likely to occur in the pattern transfer step by exposure. In this environment, it is extremely significant to ensure a sufficient focus latitude (DOF) during exposure.

As is well known, a photomask for manufacturing a display device has a large size, and in a wet process (development or wet etching) in the photomask manufacturing process, the CD (line width) uniformity at any position on the surface is improved. It is not easy to secure. It is important to secure a sufficient depth of focus (DOF) in the exposure process in order to keep the final CD accuracy within the specified allowable range, and it is desirable that other performance is not deteriorated accordingly. ..

The present invention is a photomask provided with a transfer pattern formed by patterning a semi-translucent film and a low-translucent film formed on a transparent substrate. FIG. 1 illustrates a schematic plan view of a transfer pattern included in the photomask of the present invention.

As shown in FIG. 1, the transfer pattern formed on the transparent substrate includes a main pattern having a diameter W1 (μm) and an auxiliary pattern having a width d (μm) arranged in the vicinity of the main pattern. In addition, a low light-transmitting portion is formed in a region other than where the main pattern and the auxiliary pattern are formed.

Here, let T1 be the transmittance of light having a representative wavelength within the wavelength range of the i-line to g-line that is transmitted through the auxiliary pattern, and T3 be the transmittance of light having the representative wavelength that is transmitted through the low light-transmitting portion. The distance between the center of the main pattern and the center of the auxiliary pattern in the width direction is P (μm). At this time, the photomask of the present invention satisfies the following relationship.
0.8 ≤ W1 ≤ 4.0 (1)

1.0 <P ≤ 5.0 (3)
T3 <T1 (4)

In the above formula, T1 is preferably T1≧30.

The light transmittances T1 and T3 here are based on the transmittance of the transparent substrate, and are determined by the layer structure of the corresponding portion.

A schematic cross-sectional view of such a transfer pattern can be shown, for example, in FIG. This will be described as a first mode of the photomask of the present invention, and will be described with reference to FIG.

In this aspect, the main pattern is formed of a light-transmitting portion in which the transparent substrate is exposed. A film having high transmittance may be formed on the main pattern. However, from the viewpoint of obtaining the maximum transmittance, it is preferable that the transparent film is not exposed on the main pattern and the transparent substrate is exposed.

In addition, the auxiliary pattern of this embodiment is composed of a semi-transparent portion in which a semi-transparent film is formed on the transparent substrate. This semi-transparent film has a phase shift amount that shifts light having a representative wavelength in the wavelength range of the i-line to the g-line by approximately 180 degrees, and has a transmittance T1 (%) with respect to the representative wavelength. Further, a portion surrounding the main pattern and the auxiliary pattern is a low light-transmitting portion in which at least a low light-transmitting film is formed on the transparent substrate. That is, in the transfer pattern shown in FIG. 1, the region other than the region in which the main pattern and the auxiliary pattern are formed is the low light-transmitting portion. As shown in FIG. 3A, in this embodiment, the low light-transmitting portion has a semi-light-transmitting film and a low light-transmitting film laminated on a transparent substrate. In the low light-transmitting portion, a semi-light-transmitting film and a low light-transmitting film having a transmittance of light having a representative wavelength of T2 (%) are arranged in this order on a transparent substrate, or in the reverse order. Can be laminated with.

The low light-transmitting portion of the photomask of the present invention has a predetermined low transmittance with respect to the representative wavelength of the exposure light. That is, for light having a representative wavelength in the wavelength range of the i-line to the g-line, the low light-transmitting portion has a transmittance T3 (%) lower than the transmittance T1 (%) of the auxiliary pattern including the semi-light-transmitting portion. Hold. Therefore, in the present mode (FIG. 3A) in which the low light-transmitting portion is formed by stacking the semi-light-transmitting portion and the low light-transmitting portion,
T3 <T1
Therefore, the transmittance T2 (%) of the low light-transmitting film may be selected to adjust the transmittance T3 (%) of the low light-transmitting portion.

Here, when the diameter (W1) of the main pattern is set to 4 μm or less, a fine main pattern (w1>W2) having a diameter W2 (μm) (where W1>W2) is provided on the transfer target corresponding to this main pattern. Hole pattern) can be formed.

Specifically, W1 (μm) is represented by the following formula (1)
0.8 ≤ W1 ≤ 4.0 (1)
It is preferable that the relationship be satisfied. At this time, the diameter W2 (μm) of the main pattern (hole pattern) formed on the transfer target is 3.0 (μm) or less, specifically,
0.6≦W2≦3.0
Can be

Further, the photomask of the present invention can be used for the purpose of forming a fine size pattern 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 can be more remarkably obtained. Preferably, the diameter W1 (μm) of the main pattern is
1.0≦W1≦3.0
Can be The relationship between the diameter W1 and the diameter W2 may be W1=W2, but preferably W1>W2. That is, when β (μm) is the bias value,
β=W1-W2>0 (μm)
When
0.2≦β≦1.0,
More preferably,
0.2≦β≦0.8
Can be In this case, as will be described later, advantageous effects such as reduction of the loss of the resist pattern on the transferred body can be obtained.

In the above description, the diameter W1 of the main pattern means the diameter of a circle or a numerical value approximate to it. For example, when the shape of the main pattern is a regular polygon, the diameter W1 of the main pattern is the diameter of the 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 transferred main pattern is the same in that the diameter of the circle or a numerical value approximate to the diameter is used.

Of course, when a finer pattern is to be formed, W1 can be 2.5 (μm) or less, or 2.0 (μm) or less, and further, W1 can be 1.5 (μm). The present invention can be applied as follows.

The preferred range of the diameter W1 of the main pattern in the photomask of the present invention, the diameter W2 of the main pattern on the transferred body, and the setting of the bias is in the following second to sixth aspects of the present invention. The same can be applied to a photomask.

The phase difference φ between the main pattern and the auxiliary pattern is about 180 degrees with respect to the representative wavelength of the exposure light used for exposing the photomask of the present invention having such a transfer pattern. That is, the phase difference φ1 between the light of the above-mentioned representative wavelength that transmits the main pattern and the above-mentioned representative wavelength that transmits the auxiliary pattern becomes approximately 180 degrees. Approximately 180 degrees means 120 to 240 degrees. Preferably, the phase difference φ1 is 150 to 210 degrees.

The photomask of the present invention has a remarkable effect when using the exposure light including the i-line, the h-line, or the g-line, and therefore the exposure light including at least one of the i-line, the h-line, and the g-line is used. Can be used. In particular, it is preferable to apply broad wavelength light including i-line, h-line, and g-line as exposure light. In this case, the representative wavelength can be any of i-line, h-line, and g-line. For example, the photomask of the present invention can be formed by using the h-line as a representative wavelength.

In order to form such a phase difference, the main pattern is a light-transmitting part in which the main surface of the transparent substrate is exposed, and the auxiliary pattern is a semi-light-transmitting film formed by forming a semi-light-transmitting film on the transparent substrate. The amount of phase shift of this semi-transmissive film with respect to the above-mentioned representative wavelength may be about 180 degrees.

Regarding the preferable range of the phase difference between the main pattern and the auxiliary pattern and the wavelength of the exposure light applied to the photomask of the present invention, the photomask of the present invention according to the following second to sixth aspects is also applicable. , The same.

In the photomask of the first mode, that is, in the photomask shown in FIG. 3A, the light transmittance T1 of the semi-light-transmitting portion can be set as follows. That is, when the transmissivity of the semitransparent film formed in the semitransparent portion is T1 (%),
30 ≤ T1 ≤ 80
And More preferably,
40 ≤ T1 ≤ 75
Is. The transmittance T1 (%) is the transmittance of the above-mentioned representative wavelength with reference to the transmittance of the transparent substrate.

In the photomask of the present invention, the low light-transmitting portion which is arranged in the area other than the area where the main pattern and the auxiliary pattern are formed and which is formed around the main pattern and the auxiliary pattern can be configured as follows. ..

The low light-transmitting portion may be one that does not substantially transmit the exposure light (light having a representative wavelength in the wavelength range of i-line to g-line). In this case, even if a low light-transmitting film is used alone (that is, a light-shielding film) that does not substantially transmit the above-mentioned representative wavelength, and T3≦0.01, that is, the optical density OD≧2, is applied. Alternatively, a laminated film of a low light-transmitting film and a semi-light-transmitting film may be used as a substantial light-shielding film.

Alternatively, the low light-transmitting portion may transmit the exposure light within a predetermined range. However, when the exposure light is transmitted in a predetermined range, the transmittance T3 (%) of the low light-transmitting portion (here, in the case of a lamination of a semi-light-transmitting film and a low light-transmitting film, the lamination Transmittance)
T3 <T1
To meet. Preferably,
0 ≤ T3 <30
More preferably,
0 <T3 ≤ 20
Meet The transmittance T3 (%) is also the transmittance of the above-mentioned representative wavelength when the transmittance of the transparent substrate is used as a reference.

Further, when the low light-transmitting portion transmits the exposure light with a predetermined transmittance in this way, the phase difference φ3 between the light transmitted through the low light-transmitting portion and the light transmitted through the light-transmitting portion is 90 degrees or less. Is preferably 60 degrees or less. The expression "90 degrees or less" means that the phase difference is "(2n-1/2)? to (2n+1/2)? (where n is an integer)" in radians. Similar to the above, it is calculated as a phase difference with respect to the representative wavelength included in the exposure light.

Therefore, in this case, the low light-transmitting film used for the photomask of this embodiment has a single property (T2(%)) of less than 30(%) (that is, 0<T2<30). The phase shift amount (φ2) is preferably about 180 degrees. Approximately 180 degrees means 120 to 240 degrees. Preferably, the phase difference φ1 is 150 to 210 degrees. As a result, the phase shift characteristic of the low light-transmissive portion formed by stacking can be set to φ3 within the above range.

Similarly to the above, the transmittance here is the transmittance of the above-mentioned representative wavelength when the transmittance of the transparent substrate is used as a reference.

In the transfer pattern, when the width of the auxiliary pattern is d (μm),

When the above holds, the excellent effect of the invention can be obtained. At this time, 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 is
1.0 <P ≤ 5.0
It is preferable that the relationship

More preferably, the pitch P is
1.5 <P ≤ 4.5
Can be

In the present invention, the auxiliary pattern has an effect of artificially acting like a dense pattern (Dense Pattern) on the isolated main pattern by design, but when the above relational expression is satisfied, The exposure lights that have passed through the pattern and the auxiliary pattern have a good interaction with each other, and can exhibit excellent transferability as shown in Examples described later.

The width d (μm) of the auxiliary pattern is a dimension below the resolution limit under the exposure conditions (exposure device used) applied to the photomask of the present invention, and as a specific example,
d ≧ 0.7
More preferably,
d ≧ 0.8
More preferably, the width d (μm) of the auxiliary pattern is 1 (μm) or more.

Further, d≦W1 is preferable, and d<W1 is more preferable.

Further, more preferably, the relational expression of the above (2) is the following expression (2)-1, and even 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 to this. For example, as illustrated in FIG. 2, the main pattern of the photomask may have a rotationally symmetrical shape including an octagon and a circle. The center of rotational symmetry can be the center that serves as the reference for P.

The shape of the auxiliary pattern of the photomask shown in FIG. 1 is an octagonal band, but the present invention is not limited to this. It is preferable that the shape of the auxiliary pattern is a shape in which a rotation target having a symmetry of three times or more has a given width with respect to the center of the hole pattern. The preferable shapes of the main pattern and the auxiliary pattern are the shapes illustrated in FIGS. 2A to 2F, and the design of the main pattern and the design of the auxiliary pattern are shown in FIGS. 2A to 2F. Different ones may be combined.

For example, it is exemplified that the outer periphery of the auxiliary pattern is a regular polygon such as a square, a regular hexagon, a regular octagon, a regular decagon (preferably a regular 2n polygon, where n is an integer of 2 or more) or a circle. It The shape of the auxiliary pattern is preferably a shape in which the outer circumference and the inner circumference of the auxiliary pattern are substantially parallel, that is, a shape such as a regular polygon or a circular band having a substantially constant width. This strip shape is also called a polygonal strip or a circular strip. As the shape of the auxiliary pattern, it is preferable that such a regular polygonal band or a circular band surrounds the main pattern. At this time, the transmitted light of the main pattern and the transmitted light of the auxiliary pattern can be made to have almost the same balance of light amount, 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, that is, when the photomask of the present invention is used in combination with a photoresist for manufacturing a display device, an auxiliary pattern is formed on the transferred material. It is possible to reduce the resist loss in the corresponding portion.

Alternatively, the shape of the auxiliary pattern may be a shape in which a part of the polygonal band or the circular band is missing without completely surrounding the periphery of the main pattern. The shape of the auxiliary pattern may be, for example, a shape in which the corners of a quadrangular band are missing, as shown in FIG.

Incidentally, other patterns may be additionally used in addition to the main pattern and the auxiliary pattern of the present invention as long as the effects of the present invention are not impaired.

An example of the method for manufacturing the photomask of this embodiment will be described below with reference to FIG.

As shown in FIG. 4A, a photomask blank is prepared.

In this photomask blank, a semi-transparent film and a low-translucent film are formed in this order on a transparent substrate made of glass or the like, and a first photoresist film is further applied.

The semi-transmissive film has a transmittance of 30 to 80 (%) (T1 (%) on the main surface of the transparent substrate when i-line, h-line, or g-line is a representative wavelength. Where 30≦T1≦80), more preferably 40 to 75 (%), and the phase shift amount with respect to this representative wavelength is about 180 degrees. With such a semi-transparent film, the transmitted light phase difference between the main pattern including the light-transmitting portion and the auxiliary pattern including the semi-light-transmitting portion can be approximately 180 degrees. Such a semi-transparent film shifts the phase of light having a representative wavelength in the wavelength range of the i-line to the g-line by approximately 180 degrees. As a method of forming the semi-transparent film, a known method such as a sputtering method can be applied.

The semi-transparent film is preferably made of a material that satisfies the above-mentioned transmittance and retardation and is wet-etchable as described below. However, if the amount of side etching that occurs during wet etching becomes too large, inconveniences such as deterioration of CD accuracy and destruction of the upper layer film due to undercut occur, so the film thickness range is preferably 2000 Å or less. For example, it is in the range of 300 to 2000Å, more preferably 300 to 1800Å. Here, CD is a critical dimension and is used in the present specification to mean a pattern line width.

Further, in order to satisfy these conditions, the semitransparent film material preferably has a refractive index of 1.5 to 2.9 at a representative wavelength (for example, h line) contained in the exposure light. More preferably, it is 1.8 to 2.4.

Further, in order to sufficiently exert the phase shift effect, it is preferable that the pattern cross section (the surface to be etched) formed by the wet etching is close to the perpendicular to the main surface of the transparent substrate.

In consideration of the above properties, as the film material of the semi-transparent film, a material containing at least one of Zr, Nb, Hf, Ta, Mo and Ti and Si, or an oxide or nitride of these materials is used. , Oxynitride, carbide, or material containing oxynitride carbide.

A low light-transmitting film is formed on the semi-light-transmitting film of the photomask blank. As a film forming method, a known means such as a sputtering method can be applied as in the case of the semi-transparent film.

The low light-transmitting film of the photomask blank can be a light-shielding film that does not substantially transmit the exposure light. Alternatively, it may have a predetermined low transmittance for the representative wavelength of the exposure light. The low light-transmitting 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 for light having a representative wavelength in the wavelength range of the i-line to the g-line. %).

When the low light-transmitting film can transmit the exposure light, the transmittance and the phase shift amount of the low light-transmitting film with respect to the exposure light are the transmittance and the phase shift amount of the low light-transmitting portion of the photomask of the present invention. Is required to be achieved. Preferably, in the laminated state of the low light-transmitting film and the semi-light-transmitting film, the transmittance T3 (%) for the light having the representative wavelength of the exposure light is T3<30, preferably T3≦20, and further, the phase shift The amount φ3 is 90 (degrees) or less, and more preferably 60 (degrees) or less.

The properties of the low light-transmitting film alone are such that they do not substantially transmit light of the above-mentioned representative wavelength, or have a transmittance (T2(%)) of less than 30(%) (that is, 0< It is preferable that T2<30) and the phase shift amount (φ2) is approximately 180 degrees. Approximately 180 degrees means 120 to 240 degrees. Preferably, the phase difference φ1 is 150 to 210 (degrees).

The material of the low light-transmitting film of the photomask blank may be Cr or a compound thereof (oxide, nitride, carbide, oxynitride, or oxynitride carbide), or Mo, W, Ta, or Ti. It may be a silicide of a metal containing it, or a compound of the above silicide. However, the material of the low light-transmitting film of the photomask blank is preferably a material that can be wet-etched like the semi-light-transmitting film and has etching selectivity with respect to the material of the semi-light-transmitting film. That is, it is desirable that the low light-transmitting film has resistance to the etching agent for the semi-light-transmitting film, and that the semi-light-transmitting film has resistance to the etching agent for the low light-transmitting film.

A first photoresist film is further applied on the low light-transmitting film of the photomask blank. Since the photomask of the present invention is preferably drawn by a laser drawing apparatus, a photoresist suitable for it is used. The first photoresist film may be a positive type or a negative type, but will be described below as a positive type.

Next, as shown in FIG. 4B, drawing is performed on the first photoresist film by using a drawing device with drawing data based on the transfer pattern (first drawing). Then, the low light-transmitting film is wet-etched using the first resist pattern obtained by the development as a mask. As a result, a region serving as the low light-transmitting portion is defined, and a region of the auxiliary pattern (low light-transmitting film pattern) surrounded by the low light-transmitting portion is defined. As the etchant for wet etching (wet etchant), a known one suitable for the composition of the low light-transmitting film to be used can be used. For example, if the film contains Cr, cerium ammonium nitrate or the like can be used as the wet etchant.

Next, as shown in FIG. 4C, the first resist pattern is peeled off.

Next, as shown in FIG. 4D, a second photoresist film is applied to the entire surface including the formed low light-transmissive film pattern.

Next, as shown in FIG. 4E, second drawing is performed on the second photoresist film to form a second resist pattern formed by development. The semi-transmissive film is wet-etched using the second resist pattern and the low-transmissive film pattern as a mask. By this etching (development), a region of the main pattern is formed, which is formed of a light-transmitting portion that exposes the transparent substrate. The second resist pattern covers an area serving as an auxiliary pattern and has an opening in an area serving as a main pattern composed of a light-transmitting portion, and the edge of the low light-transmitting film is exposed from the opening. It is preferable to size the drawing data of the second drawing. By doing so, it is possible to absorb the misalignment that occurs between the first drawing and the second drawing and prevent the CD accuracy of the transfer pattern from deteriorating. This is an effect utilizing the etching selectivity of the materials of the low light-transmitting film and the semi-light-transmitting film with respect to each other.

In the photomask of this embodiment, the semi-translucent film and the low-translucent film may be made of materials having common etching characteristics without etching selectivity, and an etching stopper film may be provided between both films. good.

That is, when the isolated hole pattern is formed on the transfer target by performing the sizing of the second resist pattern in the second drawing in this way, the misalignment occurs in the patterning of the light shielding film and the semitranslucent film. Therefore, in the transfer pattern as illustrated in FIG. 1, the centers of gravity of the main pattern and the auxiliary pattern can be precisely matched.

The wet etchant for the semi-transparent film is appropriately selected according to the composition of the semi-transparent film.

Next, as shown in FIG. 4F, the second resist pattern is peeled off to complete the photomask of the present invention shown in FIG.

In manufacturing a photomask for a display device, when etching an optical film such as a light-shielding film formed on a transparent substrate, dry etching and wet etching are used as etching applied. Either may be adopted, but wet etching is particularly advantageous in the present invention. This is because a photomask for a display device has a relatively large size, and there are various sizes. If dry etching using a vacuum chamber is applied during the manufacture of such a photomask, the size of the dry etching apparatus and the manufacturing process become inefficient.

However, there is a problem associated with applying wet etching when manufacturing such a photomask. Since wet etching has a property of isotropic etching, when a predetermined film is to be etched in the depth direction so as to be eluted, the etching also proceeds 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 F (nm), the opening of the resist pattern serving as an etching mask is 2 F (nm) from the desired slit width (that is, F (nm) on one side). ), the smaller the width of the slit, the more difficult it is to maintain the dimensional accuracy of the resist pattern opening. Therefore, it is useful that the width d of the auxiliary pattern is 1 (μm) or more, preferably 1.3 (μm) or more.

Further, when the film thickness F (nm) is large, the side etching amount also becomes large. Therefore, it is advantageous to use a film material having a phase shift amount of about 180 degrees even if the film thickness is small. It is desired that the semitransparent film has a high refractive index with respect to the wavelength. For this reason, it is preferable to use a material having a wavelength of 1.5 to 2.9, preferably 1.8 to 2.4 with respect to the above-mentioned representative wavelength to form the semitransparent film.

By the way, as the photomask of the present invention shown in FIG. 1, in addition to the above-described aspect, there is a photomask having the same optical effect by a different layer configuration.

The second aspect of the present invention has a layer structure whose cross section is shown in FIG. A schematic plan view of this photomask is as shown in FIG. 1 as in the case of the first embodiment, but the laminated structure when viewed in cross section is different. That is, in the low light-transmitting portion shown in FIG. 3B, the stacking order of the low light-transmitting film and the semi-light-transmitting film is reversed upside down, and the low light-transmitting film is arranged on the substrate side.

In this case, the design of the pattern as the photomask of the present invention, the respective parameters thereof, and the optical effect thereof are the same as those of the photomask of the first aspect, and the design design is shown in FIG. It is the same that the modified example is applicable. Also, the physical properties of the membrane materials used can be the same.

However, the photomask of the second aspect is slightly different from the first aspect in terms of the manufacturing method in the following points. Therefore, the film material to be used is not necessarily the same as the first aspect. Need not be.

For example, in the first aspect, as shown in FIG. 4A, a photomask blank in which a semi-translucent film and a low-translucent film are laminated is prepared, and a photolithography process is applied twice to the photomask blank. Although the photomask is manufactured, in the second embodiment, it is necessary to prepare the photomask blank in which only the low light-transmitting film is formed on the transparent substrate.

Then, the low light-transmitting film is first etched to form a low light-transmitting film pattern. Then, a semi-transparent film is formed on the entire surface of the substrate on which the low light-transmissive film pattern is formed, and is patterned. In this case, it is preferable to select a material that can be patterned by wet etching as in the first aspect. However, in this embodiment, it is not essential that the low light-transmitting film and the semi-light-transmitting film have resistance to each other's etchant. That is, both films can be etched even if they do not have etching selectivity with each other. Therefore, the degree of freedom in selecting the material is higher than that in the first aspect.

Next, a third aspect of the photomask of the present invention will be described with reference to FIG. Also in this aspect, the schematic plan view is the same as that in FIG. 1, and the pattern design, the respective parameters thereof, and the optical effects thereof are the same as those of the photomask of the first aspect except for the following points. The same applies to the modified example shown in FIG. 2 as the design.

The photomask of the third aspect shown in FIG. 3C is different from the photomasks of the first and second aspects in that the amount of phase shift of the semitransparent film with respect to the light of the representative wavelength is approximately The point is not limited to 180 degrees, and in relation to this, a predetermined amount of the transparent substrate is dug in the main pattern portion. That is, in the main pattern of this aspect, instead of exposing a part of the main surface of the transparent substrate used as the material, the dug surface in which a predetermined amount of the dug is formed by etching on the main surface is exposed. There is. Then, the phase difference of the representative wavelengths in the wavelength range of the i-line to the g-line that transmits each other between the auxiliary pattern having the semi-translucent film and the main pattern having the engraved portion is about 180. It is adjusted every time. Similar to the photomasks of the first and second aspects, the low light-transmitting portion includes a semi-light-transmitting film and a low light-transmitting film having a transmittance of light of a representative wavelength of T2 (%) on a transparent substrate. Can be laminated in this order or vice versa.

In the first aspect or the second aspect, depending on the material and the film thickness of the semi-transparent film, the condition of the transmittance T1 and the phase difference between the representative wavelengths transmitted through the main pattern and the auxiliary pattern are about 180 degrees. However, in the photomask of the third aspect, the composition and the film thickness of the semi-transparent film are determined by giving priority to the condition of the transmittance T1 to adjust the phase difference. There is an advantage that it can be done depending on the amount of the main pattern dug.

From this point, in the photomask of this embodiment, the amount of phase shift of the semitransparent film with respect to the light of the above-mentioned representative wavelength may be 90 degrees or less, or 60 degrees or less. It suffices to adjust the phase difference of the representative wavelengths transmitted through the main pattern and the auxiliary pattern to be approximately 180 degrees by the sum of the dug amount of the main pattern and the phase shift amount of the semi-transparent film.

Further, in the photomask of the third aspect, wet or dry etching is used for the dug formation of the transparent substrate, but more preferably dry etching is applied. Further, also in the photomask of this aspect, an etching stopper film may be provided between the semi-translucent film and the low-translucent film.

For example, a step of preparing a photomask blank in which a semi-translucent film and a low-translucent film are laminated on a transparent substrate, first removing both films in the main pattern portion by etching, and then digging and etching the transparent substrate is performed. Applicable. Then, the low light-transmitting film in the auxiliary pattern portion is removed by etching in the second photolithography step, whereby the photomask of the third aspect can be manufactured. In this case, the film material may be the same as in the first aspect.

Similar to the relationship between the first aspect and the second aspect, in the photomask of the third aspect, the order of stacking the semi-translucent film and the low-translucent film may be reversed upside down.

Next, a fourth aspect of the photomask of the present invention will be described with reference to FIG. Also in this mode, the schematic plan view is as shown in FIG. In the fourth aspect, similar to the third aspect, the engraving is formed in the transparent substrate in the main pattern portion, but unlike the third aspect, the semitransparent film is not used, and the transparent substrate in the auxiliary pattern portion is used. (Part of the main surface) is exposed. Then, by selecting the digging depth of the main pattern portion, the phase difference of the light of the representative wavelength transmitted through each of the main pattern and the auxiliary pattern becomes about 180 degrees, as in the first to third aspects. There is.

In the fourth aspect, since the semi-translucent film does not exist in the auxiliary pattern portion, the transmittance (T1) is 100(%). In this case, the number of times of film formation can be reduced, and as a result, advantages such as improvement in production efficiency and reduction in defect occurrence probability can be obtained as compared with the third aspect.

In this case, T1=100(%) is applied to the equation (2),

That is,
0.5 ≤ d ≤ 1.5 (2)
Becomes Preferably, d<W1.

The low light-transmitting film used for the photomask of the fourth aspect does not have to have a phase shift amount for the light of the above-mentioned representative wavelength of about 180 degrees, and preferably 90 degrees or less. More preferably, it is 60 degrees or less.

Also in the photomask of the fourth aspect, the design of the pattern shown in FIG. 1, the parameters other than those specifically mentioned, and the optical effects thereof are the same as those of the photomask of the first aspect. The same applies to the modification shown in FIG. Further, the film material used for the low light-transmitting film and the physical properties thereof can be the same as those in the first aspect. That is, the low light-transmitting portion may have a structure in which a low light-transmitting film having a transmittance of light having the representative wavelength of T2(%) (=T3(%)) is formed on the transparent substrate. ..

By the way, the fifth mode (FIG. 3E) is obtained by reversing the cross-sectional structure of the main pattern and the auxiliary pattern in the fourth mode. In the main pattern of the fifth aspect, a part of the main surface of the transparent substrate is exposed, and the auxiliary pattern is a dug in the main surface of the transparent substrate. That is, instead of the transparent substrate digging formation of the main pattern portion, by digging the transparent substrate of the auxiliary pattern portion, the phase difference of the light of the above-mentioned representative wavelength that passes through the main pattern and the auxiliary pattern is set to about 180 degrees. There is. Even in this case, it goes without saying that the design in plan view and the optical effect thereof are the same as those in the fourth aspect. Further, there is no particular difference in the manufacturing method or the film material to be applied. Therefore, in the low light-transmitting portion of the fifth aspect, a low light-transmitting film having a transmittance of light of a representative wavelength of T2(%) (=T3(%)) is formed on the transparent substrate.

The sixth aspect of the present invention shown in FIG. 3(f) is different from the configuration adopted in the first to fifth aspects (in FIG. 3(f), the photomask cross-sectional schematic diagram of the first aspect is representative. (The figure is used), and the possibility of adding a light-shielding film pattern is shown. This is worth considering when the low light-transmitting film has a substantial transmittance.

That is, in the vicinity of the main pattern and the auxiliary pattern, the interference effect of the light of the opposite phase is utilized, but in the region of the low light-transmitting portion separated from the above, the presence of light passing through the low light-transmitting film is unnecessary. However, there is a risk that there is a demerit that the amount of residual film of the resist pattern formed on the transferred body is reduced. In order to eliminate this risk, it is also useful to add a light-shielding film pattern to completely shield light in the region of the low light-transmitting portion which is separated from the main pattern and the auxiliary pattern.

Therefore, in the present invention, the use of such a light-shielding film pattern is not hindered unless the function and effect are impaired. The light-shielding film refers to a film having an OD (optical density) of 2 or more, which does not substantially transmit exposure light (light having a representative wavelength in the above range of i line to g line). Examples of the material include those containing chromium (Cr) as a main component.

The present invention includes a method for manufacturing a display device, which includes a step of exposing the above-described photomask of the present invention with an exposure device to transfer the transfer pattern onto a transfer-receiving member to form a hole pattern. ..

In the method for manufacturing the display device of the present invention, first, the above-described photomask of the present invention is prepared. Next, the transfer pattern is exposed using an exposure device having a numerical aperture (NA) of 0.08 to 0.20 and an exposure light source including at least one of i-line, h-line and g-line. A hole pattern having a diameter W2 of 3.0 μm or less, preferably 0.6 to 3.0 μm is formed on the transfer target. The exposure light source of the exposure apparatus preferably includes i-line, h-line and g-line. For the exposure, it is common and advantageous to apply a 1× exposure.

The exposure machine used for transferring the transfer pattern using the photomask of the present invention is a system that performs projection exposure at equal magnification and includes the following. That is, it is an exposure machine used for LCD (liquid crystal display device) (or FPD, liquid crystal), and its configuration is such that the numerical aperture (NA) of the optical system is 0.08 to 0.15 (coherence factor (NA). σ) is 0.4 to 0.9) and has a light source (also referred to as a broad wavelength light source) containing at least one of i-line, h-line and g-line in exposure light. However, it is of course possible to apply the present invention and obtain the effects of the present invention even in an exposure apparatus having a numerical aperture NA of 0.10 to 0.20.

The light source of the exposure apparatus to be used may be modified illumination (such as annular illumination), but even non-deformed illumination provides the excellent effects of the invention.

The present invention provides a semi-transmissive film and a low-translucent film (and, if necessary, a light-shielding film) on a transparent substrate as a raw material for the photomask of the first to third aspects (and the sixth aspect to which the invention is applied). ) Is used for the photomask blank. Then, a resist film is further applied on the surface to form a photomask.

The physical properties, film quality, and composition of the semi-translucent film and the low-translucent film are as described above.

That is, the semitransparent film of the photomask blank preferably has a transmittance T1 of 30 to 80 (%) with respect to a representative wavelength in the wavelength range of 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 film thickness having a phase shift amount of about 180 degrees. Since the semitransparent film having such a refractive index has a desired phase shift amount even if it is sufficiently thin, the wet etching time of the semitransparent film can be shortened. As a result, side etching of the semi-transparent film can be suppressed.

Further, in all aspects of the photomask of the present invention, the photomask blank on which the low light-transmissive film is formed can be used for manufacturing.

As the low light-transmitting film, a film that does not substantially transmit the light having the representative wavelength or a film that has a transmittance of less than 30% can be used. Further, the phase shift amount with respect to the representative wavelength within the i-line to g-line range of the low light-transmitting film is about 180 degrees in the photomask according to the first and second aspects, and the third, fourth and fifth aspects In the photomask according to (4), the angle may be 90 degrees or less, more preferably 60 degrees or less.

Transfer performances of three types of photomasks (Comparative Examples 1-1 and 1-2 and Example 1) shown in FIG. 5 were compared and evaluated by optical simulation. That is, what transfer performance is exhibited when the exposure conditions are set in common for three photomasks having a transfer pattern for forming a hole pattern with a diameter of 2.0 μm on the transfer target material? An optical simulation was conducted for the above.

(Comparative Example 1-1)
As shown in FIG. 5, the photomask of Comparative Example 1-1 has a so-called binary mask pattern formed of a light shielding film pattern formed on a transparent substrate. In the photomask of Comparative Example 1-1, the main pattern made of the transparent portion where the transparent substrate is exposed is surrounded by the light shielding portion. The diameter W1 (one side of the square) of the main pattern is 2.0 (μm).

(Comparative Example 1-2)
As shown in FIG. 5, the photomask of Comparative Example 1-2 is formed by patterning a semitransparent film having an exposure light transmittance (to the h line) of 5% and a phase shift amount of 180 degrees. Further, it is a halftone type phase shift mask having a main pattern composed of a square light transmitting part having one side (diameter) (that is, W1) of 2.0 (μm).

(Example 1)
As shown in FIG. 5, the photomask of Example 1 has the transfer pattern of the present invention. Here, the main pattern is a square having one side (diameter) (that is, W1) of 2.0 (μm), and the auxiliary pattern is an octagonal band having a width d of 1.3 (μm). The pitch P, which is the distance from the center of the width, was 4 (μm).

The auxiliary pattern is based on the assumption of the photomask of the first aspect, which is formed by forming a semi-translucent film on a transparent substrate. The exposure light (to the h-line) transmittance T1 of this semi-transparent film is 70 (%), and the phase shift amount is 180 degrees. Further, the low light-transmitting portion surrounding the main pattern and the auxiliary pattern is made of a light-shielding film (OD>2) that does not substantially transmit the exposure light.

In each of the photomasks of Comparative Examples 1-1 and 1-2 and Example 1, the diameter W2 is 2.0 μm (W1=W2) on the transferred material, that is, formed on the transferred material. The diameter W2 is the same as the diameter W1 of the main pattern of the transfer pattern of the photomask.). The exposure conditions applied in the simulation are as follows. That is, the exposure light had a broad wavelength including i-line, h-line, and g-line, and the intensity ratio was g-line:h-line:i-line=1:0.8:1.

The optical system of the exposure apparatus has an NA of 0.1 and a coherence factor σ of 0.5. The film thickness of the positive photoresist for obtaining the cross-sectional shape of the resist pattern formed on the transferred material was 1.5 μm.

Performance evaluation of each transfer pattern under the above conditions is shown in FIG. FIG. 6 shows the aerial image of light intensity formed on the transferred material and the cross-sectional shape of the resist pattern formed thereby.

(Optical evaluation of photomask)
For example, in order to transfer a fine light-transmitting pattern having a small diameter, the exposure light after passing through the photomask must have a good aerial image formed on the transfer target, that is, the profile of the transmitted light intensity curve. Specifically, the slope forming the peak of the transmitted light intensity is sharp and rises nearly vertically, and the absolute value of the peak light intensity is high (when a sub-peak is formed in the surroundings, Is relatively high with respect to its strength).

When quantitatively evaluating the photomask from the optical performance, the following indexes can be used.

(1) Depth of focus (DOF)
The depth of focus to be within ±10% of the target CD. When the value of DOF is high, the flatness of the transferred material (for example, the panel substrate for the display device) is less likely to be affected, a fine pattern can be reliably formed, and its CD (line width) variation can be suppressed.

(2) MEEF (Mask Error Enhancement Factor)
It is a numerical value showing the ratio of the Mask CD error and the CD error of the pattern formed on the transferred material. The lower the MEEF, the smaller the CD error of the pattern formed on the transferred material.

(3) Eop
Eop is a particularly important evaluation item in a photomask for manufacturing a display device. This is the amount of exposure light required to form the pattern size to be obtained on the transfer target. Since a photomask size is large in manufacturing a display device (for example, one side of the main surface is a square or a rectangle of about 300 to 1400 mm), a photomask having a low Eop value can be used to increase the speed of scan exposure. , The production efficiency is improved.

Based on the above, when the performance of each sample to be simulated is evaluated, as shown in FIG. 5, the photomask of Example 1 has a depth of focus (DOF) of 55 μm or more, which is much higher than that of the comparative example. In terms of superiority, it exhibits stable pattern transferability. This means that the value of MEEF is small and the CD accuracy of a fine pattern is high.

Furthermore, the Eop value of the photomask of Example 1 is very small. This shows that in the case of the photomask of Example 1, the exposure time does not increase or can be shortened even when manufacturing a large-area display device.

Further, referring to the aerial image of transmitted light intensity shown in FIG. 6, in the case of the photomask of Example 1, the peak of the main pattern portion is made higher than the level (Eth) which is the threshold value at which the resist is exposed. It can be seen that the slope of the peak can be sufficiently raised (close to the surface of the transferred material). This point is superior to Comparative Examples 1-1 and 1-2. Here, the light transmitted through the auxiliary pattern is used to enhance the light intensity at the main pattern position, thereby achieving an increase in Eop and a decrease in MEEF. In the photomask of Example 1, side peaks are generated on both sides of the transfer image position of the main pattern, but since it is equal to or less than Eth, transfer of the main pattern is not affected.

A method for reducing the loss of the resist residual film due to the side peak will be described below.

The design of the transfer pattern formed on the photomask was changed, and simulations were performed using the samples of Comparative Example 2-1, Comparative Example 2-2 and Example 2 shown in FIG. Both are different from the samples (Comparative Example 1-1, Comparative Example 1-2 and Example 1) in that the diameter W1 of the main pattern is 2.5 (μm).

(Comparative Example 2-1)
As shown in FIG. 7, the photomask of Comparative Example 2-1 is a so-called binary mask pattern composed of a light shielding film pattern formed on a transparent substrate. In the photomask of Comparative Example 2-1, the main pattern made of the transparent portion where the transparent substrate is exposed is surrounded by the light shielding portion. The diameter W1 (one side of the square) of this main pattern is 2.5 (μm).

(Comparative Example 2-2)
As shown in FIG. 7, the photomask of Comparative Example 2-1 was formed by patterning a semitransparent film having an exposure light transmittance (to the h line) of 5% and a phase shift amount of 180 degrees. Further, it is a halftone type phase shift mask having a main pattern composed of a quadrangular light transmitting portion having a main pattern diameter W1 (one side of a square) of 2.5 (μm).

(Example 2)
As shown in FIG. 7, the photomask of Example 2 is the transfer pattern of the present invention. The main pattern of the photomask of Example 2 is a square having a main pattern diameter W1 (square side) of 2.5 (μm), and the auxiliary pattern is an octagonal band having a width d of 1.3 (μm). The pitch P, which is the distance between the center of the main pattern and the center of the width of the auxiliary pattern, was set to 4 (μm). Here again, the photomask of Example 2 is assumed to be the photomask of the first aspect.

It is assumed that a hole pattern having a diameter of 2.0 μm is formed on the transferred material by using the photomasks of Comparative Example 2-1, Comparative Example 2-2 and Example 2. That is, the mask bias (β=W1−W2) of these photomasks was set to 0.5 (μm). The exposure conditions applied by the simulation are the same as those of the photomasks of Comparative Examples 1-1 and 1-2 and Example 1 described above.

As is clear from the data shown in FIG. 7, when the photomask of Example 2 was used, excellent performance was exhibited for Comparative Examples 2-1 and 2-2 together with excellent DOF and MEEF. .. In the photomask of Example 2, the DOF has a numerical value exceeding 35 μm.

Further, referring to the aerial image of transmitted light intensity and the resist pattern cross-sectional shape on the transferred body shown in FIG. 8, the excellent characteristics of the sample of Example 2 are further clarified. As shown in FIG. 8, when the photomask of Example 2 is used, the peak corresponding to the main pattern is significantly higher than the side peaks formed on both sides, and resist damage hardly occurs.

From the above results, in the case of pattern transfer using the photomask of the present invention, the mask bias β is about 0.5 (μm), specifically, in the range of 0.2 to 1.0 (μm). It has been clarified that an excellent transferred image that is more practically usable can be obtained with a certain transfer pattern.

From the above, the excellent performance of the photomask of the present invention was confirmed. In particular, if the photomask of the present invention is used, it is significant that MEEF can obtain a numerical value of 2.5 or less in a fine pattern of 2 μm or less in future display device manufacturing.

The use of the photomask of the present invention is not particularly limited. The photomask of the present invention can be preferably used when manufacturing display devices including liquid crystal display devices and EL display devices.

According to the photomask of the present invention, it is possible to control the mutual interference of the exposure light transmitted through both the main pattern and the auxiliary pattern, reduce the zero-order light at the time of exposure, and relatively increase the proportion of ±first-order light. You can Therefore, the aerial image of transmitted light can be significantly improved.

In order to obtain such advantageous effects, it is advantageous to use the photomask of the present invention for forming isolated hole patterns such as contact holes often used in liquid crystals and EL devices. As a kind of pattern, a large number of patterns are arrayed with a certain regularity, and these densely affect each other (Dense pattern) and an isolated pattern in which such regular array pattern does not exist in the surroundings. It is often called by distinguishing it from a pattern. The photomask of the present invention is preferably applied when an isolated pattern is to be formed on a transfer target.

Additional optical films and functional films may be used in the photomask of the present invention as long as the effects of the present invention are not impaired. For example, a light-shielding film may be formed in a region other than the transfer pattern in order to prevent the inconvenience that the light transmittance of the low light-transmitting film interferes with inspection and position detection of the photomask. Further, in the semi-transparent film, an antireflection layer for reducing the reflection of drawing light or exposure light may be provided on the surface thereof.

Claims (15)

A photomask comprising a transfer pattern formed on a transparent substrate, wherein the transfer pattern comprises:
A main pattern of diameter W1 (μm),
An auxiliary pattern having a width d (μm) arranged in the vicinity of the main pattern,
A low light-transmitting portion arranged in a region other than the area where the main pattern and the auxiliary pattern are formed,
The phase difference between the representative wavelength in the wavelength range of the i-line to the g-line that transmits the main pattern and the representative wavelength that transmits the auxiliary pattern is about 180 degrees,
The transmittance of the light of the representative wavelength that passes through the auxiliary pattern is T1 (%),
The transmittance of the light of the representative wavelength that passes through the low light-transmitting portion is T3 (%),
A photomask, characterized in that when the distance between the center of the main pattern and the center of the auxiliary pattern in the width direction is P (μm), the following formulas (1) to (4) are satisfied.
0.8 ≤ W1 ≤ 4.0 (1)

1.0 <P ≤ 5.0 (3)
T3 <T1 (4) The photomask according to claim 1, wherein the auxiliary pattern is formed by forming a semi-transparent film having a transmittance of T1 (%) on the transparent substrate on the transparent substrate. The photomask according to claim 2, wherein the transmissivity T1 (%) of the semi-transparent film satisfies the following expression (5).
30 ≤ T1 ≤ 80 (5) The photomask according to claim 2, wherein the width d of the auxiliary pattern is 1 (μm) or more. The main pattern is formed by exposing a part of the main surface of the transparent substrate,
The auxiliary pattern is formed by forming the semi-transparent film on the transparent substrate,
The low light-transmissive portion includes the semi-transmissive film and the low light-transmissive film having a transmittance of light of the representative wavelength of T2 (%) on the transparent substrate in this order or vice versa. The photomask according to claim 2, wherein the photomask is laminated in this order. The main pattern is a dug formed on the main surface of the transparent substrate,
The auxiliary pattern is formed by forming the semi-transparent film on the transparent substrate,
The low light-transmissive portion includes the semi-transmissive film and the low light-transmissive film having a transmittance of light of the representative wavelength of T2 (%) on the transparent substrate in this order or vice versa. The photomask according to claim 2, wherein the photomask is laminated in this order. The semi-transparent film is a material containing at least one of Zr, Nb, Hf, Ta, Mo and Ti and Si, or an oxide, nitride, oxynitride, carbide or oxynitride of these materials. The photomask according to any one of claims 2 to 6, which is made of a material containing a carbide. The photomask of claim 1, wherein the auxiliary pattern is formed by exposing the transparent substrate. The main pattern is a dug formed on the main surface of the transparent substrate,
The auxiliary pattern is formed by exposing a part of the main surface of the transparent substrate,
9. The low light-transmitting portion is formed by forming, on the transparent substrate, a low light-transmitting film having a transmittance of light of the representative wavelength of T3 (%). Photomask described. The main pattern is formed by exposing a part of the main surface of the transparent substrate,
The auxiliary pattern is a dug formed on the main surface of the transparent substrate,
9. The low light-transmitting portion is formed by forming, on the transparent substrate, a low light-transmitting film having a transmittance of light of the representative wavelength of T3 (%). Photomask described. The hole pattern having a transfer diameter W2 of 3.0 (μm) or less (where W1>W2) is formed on the transfer target corresponding to the main pattern. 10. The photomask according to any one of 10. When a difference W1−W2 between the diameter W1 of the main pattern and the transfer diameter W2 on the transfer target is set to a bias β (μm),
0.2 ≤ β ≤ 1.0 (6)
The photomask according to claim 11, wherein The transmittance T3 (%) of the low light-transmitting portion for light of the representative wavelength is
T3<30 (7)
The photomask according to claim 1, wherein the photomask satisfies the following condition. 13. The photomask according to claim 1, wherein the low light-transmitting portion is a material that does not substantially transmit the light having the representative wavelength. A step of preparing the photomask according to any one of claims 1 to 14,
The transfer pattern is exposed by using an exposure device having a numerical aperture (NA) of 0.08 to 0.20 and an exposure light source including at least one of i-line, h-line and g-line, and is transferred. And a step of forming a hole pattern having a diameter W2 of 0.6 to 3.0 (μm) on the body.