KR20150060519A - Method for manufacturing photomask, photomask and pattern transfer method - Google Patents

Abstract

The objective of the present invention is to provide a photomask capable of forming a CD on a transfer body even if the CD is a fine pattern of 3 um or less, in which the CD variation within the surface thereof is sufficiently suppressed. A method for manufacturing a photomask having a transfer pattern which includes an optical film pattern in which an optical film containing Cr is patterned and formed on a transparent substrate comprises: a step of preparing a photomask intermediate having the optical film on the transparent substrate; a modification step of modifying a membrane of the optical film by irradiating vacuum ultraviolet rays with respect to the optical film; a step of coating a photoresist layer on the modified optical film; a step of performing exposure and development on the photoresist layer and forming a resist pattern; an etching step of forming an optical film pattern by wet-etching the optical film using the resist pattern; and a step of removing the resist pattern.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a photomask, a photomask, and a pattern transfer method.

Field of the Invention [0002] The present invention relates to a photomask provided with a transfer pattern, and more particularly to a photomask which is particularly useful for manufacturing a display device and a method of manufacturing the same.

Patent Document 1 discloses a photomask blank and a photomask which are small in warpage and high in chemical resistance against acid or alkali.

Patent Document 2 discloses a method of improving the wettability of a mask substrate by irradiating ultraviolet rays using an excimer lamp or the like as a light source to a mask substrate having a microfluidicity and then performing a cleaning process with O ₃ , Thereby preventing the growth of foreign matter by effectively removing the foreign matter.

[Patent Document 1] Japanese Patent Application Laid-Open No. 2004-226593 [Patent Document 2] JP-A-2009-122313

A photomask manufactured by patterning an optical film containing Cr (hereinafter, also referred to as a Cr-based optical film) has been used in many applications due to its excellent properties. However, with the development of new photomasks and the change in required specifications, new technical problems have arisen.

At present, VA (Vertical Alignment) method or IPS (In Plane Switching) method is adopted for a liquid crystal display device. With these applications, improvement in display performance such as high-precision, high-speed display, and wide viewing angle has been demanded in addition to being bright and saving power.

For example, in a liquid crystal display device to which these methods are applied, a transparent conductive film formed in a line-and-space pattern shape is applied to a pixel electrode, and further miniaturization of such a pattern is desired in order to improve display performance of a display device . For example, it is desired to narrow the pitch width P (sum of the line width L and the space width S) of the line-and-space (L / S) pattern from 6 탆 to 5 탆 and from 5 탆 to 4 탆 . In this case, at least one of the line width L and the space width S is often less than 3 mu m. For example, L <3 탆 or L ≤ 2 탆, or S <3 탆 or S ≤ 2 탆 in many cases.

On the other hand, in the case of a thin film transistor ("TFT") used in a liquid crystal display device or an EL (electroluminescence) display device, among the plurality of patterns constituting the TFT, a contact hole formed in the passivation layer A configuration is adopted in which the insulating layer penetrates through and is connected to a connection portion on the lower layer side. At this time, if the patterns on the upper layer side and the lower layer side are accurately positioned and the shape of the contact hole is not reliably formed, the correct operation of the display device is not guaranteed. In this case, too, it is required to make the pattern finer since the display performance is improved and the device pattern is required to be highly integrated. That is, the diameter of the hole pattern is required to be less than 3 탆. For example, it is considered that a hole pattern having a diameter of 2.5 占 퐉 or less, furthermore, a diameter of 2.0 占 퐉 or less is required, and formation of a pattern having a diameter of 1.5 占 퐉 or less in the near future is also desirable.

From such a background, there is an increasing demand for a photomask for manufacturing a display device capable of coping with the miniaturization of line-and-space patterns and contact holes.

In the field of photomasks for manufacturing semiconductors (LSIs, etc.), in order to obtain resolution, a process of developing a phase shift mask using a phase shift action together with an optical system of a high NA (Numerical Aperture) . The phase shift mask is used together with a single wavelength, a short wavelength light source (such as KrF or ArF excimer laser). Thereby, high integration of various elements and the like and accompanying patterning of the photomask have been coped with.

On the other hand, in the field of lithography for manufacturing display devices, it has not been general that the above-described method is applied to improve the resolution and the depth of focus. For this reason, it can be said that the degree of integration and fineness of the pattern required for the display device was not the same as in the semiconductor manufacturing field. Actually, an optical system or a light source mounted on an exposure apparatus for manufacturing a display device (generally known as an LCD exposure apparatus or a liquid crystal exposure apparatus) is different from the one used for semiconductor manufacturing, For example, by extending the wavelength range of the light source to obtain a large amount of irradiated light, shortening the production time, etc.) have been emphasized.

When the transfer pattern of the photomask is miniaturized, it is difficult to accurately carry out the step of transferring the transferred pattern onto a transfer target body (also referred to as a thin film to be etched or a workpiece). Although the resolution limit of the above-described exposure apparatus which is actually used in the transferring process in the manufacture of the display device is about 2 to 3 占 퐉, among the transfer patterns necessary for the display device, as described above, a CD (Critical Dimension, Width) is already close to or below the required dimension.

In addition, since the mask for manufacturing a display device has a larger area than that of a mask for manufacturing a semiconductor, there is a great difficulty in uniformly transferring a transfer pattern having a CD of less than 3 mu m in the surface of the image.

The use of a mask for manufacturing a display device as described above involves difficulty in transferring a fine pattern such as CD having a size of less than 3 mu m. Therefore, various methods for improving the resolution, which have been developed for the purpose of semiconductor device manufacturing, It is considered to be applied to the field of manufacturing.

However, there are several problems in applying the above-described method directly to the manufacture of a display device. For example, a large investment is required for switching to a high-resolution exposure apparatus having a high NA (numerical aperture), and inconsistency with the price of the display device is incurred. In addition to the problem that it is difficult to apply to a display device having a relatively large area or a manufacturing time is prolonged for the change of the exposure wavelength (using a short wavelength such as an ArF excimer laser at a single wavelength) Lt; / RTI &gt;

Therefore, it is very significant if the transferability of the fine pattern can be improved by designing the transfer pattern provided in the photomask for manufacturing a display device.

In addition, as the transfer pattern becomes finer, the importance of finely and precisely performing the CD control of the transfer pattern formed on the large area photomask is also increasing. For example, a photomask blank in which a Cr-based optical film is formed on a transparent substrate is cleaned with a cleaning chemical solution using an acid or an alkali before the application of the resist. Here, it is inevitable that the Cr-based optical film is damaged by the treatment of these chemical solutions (for example, a chemical solution containing an acid), and this damage is uneven in the surface, There is a problem that unevenness of the inner reflectance occurs.

With respect to the influence of such an influence on the line width (CD) precision of the transfer pattern, it has become necessary to strictly control the pattern with the tendency to miniaturize the pattern these days.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a photomask which can stably form on a transferred body even if the CD is a fine pattern with a depth of less than 3 占 퐉,

Patent Document 1 discloses that a phase shift film such as molybdenum silicide oxide has a problem that a stress is generated after film formation and warpage of the substrate occurs or a problem that the chemical resistance is not sufficient may occur, And it is disclosed that the warpage is reduced by irradiating light having a peak wavelength of 400 to 500 nm and the retardation change after immersion in a chemical liquid is reduced. However, according to the study by the present inventors, the ultraviolet irradiation described in Patent Document 1 does not bring about the modification effect of the present invention as described below, which affects the film quality of the Cr-based optical film.

In addition, the mask substrate described in Patent Document 2 does not propose an advantageous effect that exceeds the wettability improvement of the surface of the mask substrate before O ₃ cleaning.

The gist of the present invention is as follows.

&Lt; 1 > A manufacturing method of a photomask having a transfer pattern including an optical film pattern formed by patterning an optical film containing Cr on a transparent substrate, comprising the steps of: preparing a photomask intermediate having the optical film on the transparent substrate A modification step of modifying the film quality of the optical film by irradiating the optical film with vacuum ultraviolet light; a step of applying a photoresist film on the optical film after the modification; Forming an optical film pattern by wet etching the optical film by using the resist pattern; and removing the resist pattern, wherein the step of forming the optical film comprises the steps of: In the reforming step, a modification for changing the wet etching property of the optical film with respect to the inside of the optical film Wherein the photomask further comprises a photomask.

&Lt; 2 > The method for manufacturing a photomask according to < 1 >, wherein the photomask intermediate is a photomask blank having at least the optical film formed on the transparent substrate.

&Lt; 3 > The method for manufacturing a photomask according to < 1 >, wherein the photomask intermediate is a laminated intermediate having a film pattern formed on the transparent substrate and at least the optical film formed thereon.

<4> In the step of modifying the optical film, when the thickness of the optical film is T, modification is performed to change the wet etching property of the optical film to at least T / 3 in the thickness direction from the surface The method of manufacturing a photomask according to any one of < 1 > to < 3 >

<5> The method for manufacturing a photomask according to any one of <1> to <4>, wherein an angle of an etched section of the optical film is set to 50 to 90 degrees by the etching process.

<6> The manufacturing method of a photomask according to any one of <1> to <5>, wherein the optical film is a phase shift film for shifting the phase of a representative wavelength of exposure light for exposing the photomask by approximately 180 degrees. Way.

The photomask includes a transparent portion having a transparent substrate exposed on its surface and a phase shifting portion having a phase shifting film formed to transmit a part of the exposing light and shift the phase of the representative wavelength of the exposing light by approximately 180 degrees And the optical film is the phase shift film, wherein the phase shift film is formed on the surface of the substrate, and the optical film is the phase shift film.

<8> The photomask according to any one of <1> to <7>, wherein the photomask is a photomask for manufacturing a display device to be exposed using exposure light having a wavelength range of 365 to 436 nm. &Lt; / RTI &gt;

<9> A photomask having a transfer pattern including an optical film pattern formed by patterning by wet etching, the optical film containing Cr formed on a transparent substrate, wherein when the thickness of the optical film is T, Wherein an angle of an etched end face of the optical film is in the range of 50 to 90 degrees because the film is modified in the optical film at least at a depth of T / 3 or more in the thickness direction.

<10> The photomask of <9>, wherein the optical film is a phase shift film which shifts the phase of a representative wavelength of exposure light by approximately 180 degrees.

<11> The pattern transfer method according to <9> or <10>, wherein the pattern transfer is performed using exposure light including a wavelength region of 365 to 436 nm.

According to the present invention, there is provided a photomask capable of stably forming on a transferred body even if the CD is a fine pattern with a depth of less than 3 占 퐉, / RTI &gt;

1 (a) and 1 (b) are SEM photographs of the etched section of the phase shift film in the patterned samples of the second comparative example and the second embodiment, respectively.
Fig. 2 is a schematic view (Fig. 2 (a)) of the phase shift mask of the line-and-space pattern viewed from the upper side in the simulation of the difference in phase shift effect due to the difference in cross- Sectional view (FIG. 2 (c)) of a phase shift mask of another shape, and a cross-sectional schematic diagram (FIG. 2 (d)) of a binary mask used for comparison.
Fig. 3 is a light intensity distribution curve formed on the transferred body when exposed using three kinds of photomasks used in the simulation.
4 is a view showing an example of a form of a method of manufacturing a photomask of the present invention.
5 is a schematic view for explaining the definition of the &quot; angle of the etched cross section &quot;.
Fig. 6 is a view showing another embodiment of the method of manufacturing the photomask of the present invention.
7A is a top view of the photomask of the present invention having a line-and-space pattern. FIG. 7C is a cross-sectional view of the photomask at a portion indicated by a dashed line in FIG. 7A, FIG. 7 (b) is a top view of the photomask of the present invention having a hole pattern, and FIG. 7 (d) is a cross-sectional view of the photomask at a portion indicated by the dashed line in FIG.
8A is a top view of the photomask of the present invention having a line-and-space pattern. FIG. 8C is a cross-sectional view of the photomask at a portion indicated by a chain line in FIG. 8A, 8 (b) is a top view of the photomask of the present invention having a hole pattern, and FIG. 8 (d) is a cross-sectional view of the photomask at a portion indicated by a dashed line in FIG. 8 (b).
9 is a graph showing the results of measurement of the photomask blanks of the first embodiment (FIG. 9B) and the first comparative example (FIG. 9A) after cleaning using a H ₂ SO ₄ aqueous solution, 7 is a view showing a comparison result between the light reflectance and the measurement result of the reference.
10 is a graph showing the X-ray reflectance XRR of the film density of the phase shift film for the photomask blank subjected to the VUV (Vacuum Ultra Violet) irradiation process and the photomask blank not subjected to the VUV irradiation process similar to those of the second embodiment Fig.

In the photolithography process, in order to reliably transfer a fine pattern, the light intensity distribution imparted to the resist film on the transferred body by the exposure process using a photomask becomes important. That is, when the contrast of the light intensity distribution curve is high and the profile of the resist pattern formed on the transfer body is improved, etching processing of the transfer destination body such as a display device substrate can be performed more precisely and densely have. In the photomask for a display device, the area is generally large (about 300 mm to 1800 mm on one side), uniform patterning can be performed on the entire surface, and uniformity of CD in the surface can be controlled The shape of the light intensity distribution curve formed by the exposure light is particularly important.

However, it is conceivable to use a photomask having a phase shift film (or a phase inversion layer) for fine or high-precision pattern formation or for obtaining a high resolution.

For example, it is possible to form a photomask by forming a chromium phase shift film on a transparent substrate and patterning the phase shift film using the resist pattern formed by the photoresist formed on the phase shift film as a mask do.

Here, when the phase shift film is etched using the resist pattern as a mask, it is expected that the phase shift film is faithfully patterned with respect to the resist pattern. However, it has been discovered by the present inventors that wet etching is applied to the following problems.

1 (a) shows a cross-sectional SEM photograph of the obtained phase shift film pattern when wet etching is performed using, for example, a chromium-based phase shift film with a resist pattern as a mask. 1A shows a phase shift film made of CrOCN formed on a transparent glass substrate 101 in a patterned sample of a second comparative example to be described later by using a resist pattern 103 of a positive type photoresist as a mask, Sectional SEM photograph of the phase shift film pattern 102 obtained by etching.

1 (a), the end portion of the end face of the phase shift film (PS) film 102 in contact with the etching solution is not perpendicular to the surface of the transparent glass substrate 101 (Hereinafter, also referred to as a tapered shape). This is because the upper surface side (surface side) of the PS film pattern 102 is etched faster than the lower surface side (on the side of the transparent glass substrate 101) or the central portion of the film thickness of the PS film pattern 102 In the left direction in Fig.

In order to enhance the contrast of the transfer image and improve the depth of focus by using the phase inversion of the transmitted light at the boundary between the transparent portion through which the exposure light is transmitted and the light shielding portion through which the exposure light is shielded, Photomasks are mainly used in semiconductor manufacturing fields. It is known that these phase shift masks use a phase shift film having a transmittance of about 5 to 10% for the exposure light (for example, KrF or ArF excimer laser) and shifting the phase of the exposure light by about 180 degrees.

However, since the photomask (phase shift mask) used in the field is generally manufactured by applying dry etching, a problem caused by employing the wet etching has never been realized. However, in the photomask for manufacturing a display device, wet etching is more advantageous than dry etching because the size of the photomask is relatively large as described above and the size of the photomask is various.

On the other hand, in a photomask for manufacturing display devices, a multi-gradation photomask having a transfer pattern including a semi-light-projecting portion which partially transmits exposure light is used in addition to a light-shielding portion and a light-projecting portion. This photomask has a different light transmittance of the transparent portion, the light shielding portion, and the translucent portion (light transmittance is substantially zero in the light shielding portion), thereby forming a three-dimensional step in the form of a resist pattern to be formed on the transferred body By using this, it is possible to reduce the number of steps in processing the transferred body.

The semi-light-transmitting portion in the multi-gradation photomask may be formed by forming a semi-light-transmitting film (a film having a transmittance that passes through about 20 to 80% of exposure light) on a transparent substrate.

However, at the time of manufacturing such a multi-gradation photomask, the phase difference of the exposure light transmitted through the respective boundaries between the translucent portion and the transparent portion was not set to about 180 degrees. If the phase difference is close to 180 degrees, a substantially light-shielding line pattern is formed at the boundary portion, and a problem arises that the three-dimensional shape of the resist pattern to be obtained can not be obtained.

Up to now, the problem that the cross section of the translucent film is inclined with respect to the substrate surface in the photomask for manufacturing a display device has never been realized.

The inventors of the present invention conducted simulations on how the etched end face of the phase shift film of the photomask is not perpendicular to the substrate surface but has an inclined cross-sectional shape to have an influence on the transferability of the photomask. That is, in the transfer pattern of the photomask, the phase shift effect obtained by reversing the phases of the exposure light transmitted through the respective boundaries between the transparent portion and the phase shift portion is caused by the etched cross-sectional shape of the phase shift film, And whether it will change.

<Simulation Results>

Before explaining the embodiment of the present invention, the difference in the phase shift effect due to the difference in cross-sectional shape of the phase shift film pattern will be described using the results of the above simulation.

The simulation was performed by applying the optical conditions of the exposure apparatus for manufacturing a display device. (Intensity ratio is g-line: h-line: i-line = 0.95), the numerical aperture (NA) of the optical system is 0.085, the coherence factor (?) Is 0.9 and the exposure light includes g- : 0.8: 1.0).

This simulation is performed by using a phase shift mask PSM (A) having a phase shift film pattern whose edge section is vertical in cross section, a phase shift film pattern PSM (A) having an edge section having a tapered cross section, Phase shift masks [PSMTP (A)] and binary masks (Bin). Figs. 2 (b) to 2 (d) show schematic diagrams of respective cross sections.

2 (a) is a schematic view of the line-and-space pattern used in this simulation, as viewed from the top, and shows a part of the line-and-space pattern in the PSM (A). Fig. 2 (b) is a view showing a partial cross section of the phase shift mask having the line-and-space pattern.

The phase shift mask PSM (A) has a phase shift film pattern 12a formed on the transparent substrate 11 and a light shield film pattern 14a formed thereon as shown in Fig. 2 (b) (This is referred to as a line portion). The portion of the light-shielding film pattern 14a seen from this upper surface (i.e., Fig. 2A) is the light-shielding portion 19 and part of the phase shift film pattern 12a is not covered with the light- The exposed portion is the phase shifting portion 18 and the exposed portion of the transparent substrate 11 on which nothing is stacked constitutes the transparent portion 16 (this is referred to as a space portion).

The phase shift mask PSM (A) has a line-and-space pattern with a line width L of 2.0 mu m and a space width S of 2.0 mu m (pitch P of 4.0 mu m) And phase shifting portions 18 each having a width of 0.5 占 퐉 are provided on the opposite sides of the substrate 19. The space patterns 3a, 3b and 3c are transparent portions 16 in which the transparent substrate 11 is exposed.

Here, the light shielding portion 19 is a portion where at least the light shielding film pattern 14a is formed on the transparent substrate 11, and the exposure light transmittance thereof is substantially zero. The phase shift portion 18 is a portion where the phase shift film pattern 12a with a light transmittance of 6% (i line) is formed on the transparent substrate 11 and the phase difference from the transparent portion 16 is 180 (Large line).

Next, the phase shift mask PSMTP (A) shown in Fig. 2C also has a line-and-space pattern with a line width L of 2.0 mu m and a space width S of 2.0 mu m, And have phase shift portions each having a width of 0.5 mu m at both edges of the light portion. The space pattern is formed of a transparent portion where the transparent substrate 11 is exposed. However, the phase shift portion is formed such that the film thickness of the phase shift film pattern 12a formed on the transparent substrate 11 gradually decreases from the light shielding portion side toward the light transmitting portion side (in the width direction of the line pattern) . In other words, the portion closest to the light-shielding portion has a transmittance of 6% (large line) and a phase difference of 180 degrees with respect to the light-transmitting portion (large line) , And the phase difference from the transparent portion (large line) is 20.19 degrees.

2 (d) has a line-and-space pattern with a line width L of 2.0 占 퐉 and a space width S of 2.0 占 퐉, and the line portion has a light shielding film And a light-shielding portion in which a pattern 14a is formed, and the light-transmitting portion is composed of a portion where the surface of the transparent substrate 11 is exposed.

Fig. 3 is a light intensity distribution curve formed on the transferred body when exposed using PSM (A), PSMTP (A) and Bin. The center of the line pattern 2a is set as a zero position. Here, the light intensity is 1.0 when the transmittance is 100%. When the maximum value (maximum light intensity) of the light intensity distribution curve is Imax and the minimum value (minimum light intensity) is Imin, the contrast can be calculated as (Imax-Imin) / (Imax + Imin).

Table 1 below shows numerical values of Imax, Imin, and contrast for each of the PSM (A), PSMTP (A), and Bin masks.

From these results, in the phase shift mask PSM (A) in which no taper is formed in the edge section of the phase shift film pattern (the cross sectional shape is perpendicular to the substrate), the phase shift film pattern has a phase shift The contrast is high as compared with the case of the mask [PSMTP (A)] or the binary mask (Bin).

As shown in Table 1, when the PSM (A) is used, the contrast is 0.67273. According to the examination by the present inventors, it is preferable that a contrast of 0.65 or more is obtained. It is also preferable that a value of 0.1 or less is obtained as the minimum value Imin.

Also, in PSMTP (A), the contrast is lower than Bin. Since the edge portion of the phase shift film pattern is tapered in the PSMTP (A), the transmittance is high and the phase difference from the transparent portion is reduced as it approaches the transparent portion. As a result, it can be seen that the effect of improving the contrast due to the optical interference of the inverted phase is reduced at the boundary between the phase shifting portion and the light transmitting portion.

This means that the contrast of the light intensity distribution formed on the subject has deteriorated, that is, the profile (resist cross-sectional shape) of the resist pattern formed thereon is deteriorated.

As described above, it can be seen that the effect of improving the contrast due to the optical interference of the inverted phase at the boundary between the transparent portion and the phase shifting portion is improved by making the cross section of the edge portion of the phase shift film pattern closer to the substrate surface have.

Therefore, the inventors of the present invention have studied a method of controlling the shape of the etched cross section when the Cr-based optical film such as a phase shift film is patterned by wet etching. As a result, the present inventors have found that by modifying the Cr-based optical film using a specific ultraviolet ray, the shape of the etched cross-section can be made substantially perpendicular to the substrate, and furthermore, the resistance to cleaning of the Cr- The present invention has been accomplished on the basis of these findings.

Hereinafter, the present invention will be described.

[Manufacturing Method of Photomask]

The present invention provides a method of manufacturing a photomask having a transfer pattern including an optical film pattern formed by patterning an optical film containing Cr on a transparent substrate, the method comprising the steps of: forming a photomask intermediate A step of modifying the film quality of the optical film by irradiating the optical film with a vacuum ultraviolet ray; a step of applying a photoresist film on the optical film after the modification; Forming an optical film pattern by wet-etching the optical film using the resist pattern; and removing the resist pattern, wherein the step of forming the optical film pattern includes the steps of: In the optical film reforming step, the wet etching property of the optical film is changed with respect to the inside of the optical film It will perform the modification.

Hereinafter, each step in the method of manufacturing the photomask of the present invention will be described with reference to FIG. 4 illustrating the form thereof.

&Lt; Preparation process >

In the present invention, a photomask intermediate having an optical film is prepared on a transparent substrate. This photomask intermediate may be, for example, a photomask blank according to the following production method. First, a transparent substrate 11 is prepared (Fig. 4 (a)). The material of the transparent substrate 11 is not particularly limited as long as it is a material having translucency to the exposure light used for the photomask. For example, synthetic quartz glass, soda lime glass and alkali-free glass can be mentioned as the above materials.

Then, an optical film 12 containing Cr is formed on the transparent substrate 11 (Fig. 4 (b)). The optical film 12 may be formed directly on the transparent substrate 11 or may be formed on another film formed on the transparent substrate 11. That is, in this state, the photomask blank is formed with at least the optical film 12 on the transparent substrate 11. The optical film 12 may be formed on a film pattern formed by patterning another film on a transparent substrate. That is, a laminated intermediate may be prepared. Examples of the film pattern include a light-shielding film pattern and the like.

Here, the optical film 12 may be a light shielding film that substantially shields exposure light, or may be a semitransparent film that transmits a part of exposure light. The optical film 12 is patterned to be at least a part of the transfer pattern. The optical film 12 may have an antireflection function of exposure light. The optical film 12 may transmit a part of the exposure light and shift the exposure light by a predetermined amount. Particularly preferably, the optical film 12 may be a phase shift film that shifts the phase of the exposure light by approximately 180 degrees , In this case, the following advantages can be obtained.

The thickness T of the optical film 12 may be, for example, 500 to 2000 Å, depending on the kind of the film. Preferably, the thickness T of the optical film 12 may be 1200 to 1,500 angstroms.

Next, the optical film 12 will be described in more detail. As described above, the optical film 12 may contain Cr, and Cr may be contained as a compound of Cr such as an oxide.

(CrOx), a nitride (CrNx), a carbide (CrCx), an oxide nitride (CrOxNy), a nitride carbide (CrCxNy), an oxidized carbide (CrOxCy), and the like are used as the phase shift film, , Oxynitride carbide (CrOxNyCz), and chromium fluoride (CrFx) in the phase shift film.

It is preferable that the phase shift film is a chromium-containing film having a chromium content of less than 50 atomic%. The film thickness of the phase shift film is preferably 800 to 1800 angstroms.

On the other hand, when the optical film 12 is a light-shielding film, an oxide of Cr (CrOx), a nitride of CrNx, a carbide of CrCx, a nitride of CrOxNy, a nitride of CrCxNy, , And oxynitride carbide (CrOxNyCz). More preferably, the light-shielding film constituting material can be any one of chromium carbide, chromium nitride carbide, chromium oxycarbide, or chromium oxynitride carbide.

In addition to the above-described Cr-containing material, a material containing molybdenum (Mo), silicon (Si), tantalum (Ta), hafnium (Hf), aluminum (Al), or titanium (Ti) Can be suitably used. For example, nitrides, oxides, carbides, oxynitrides, carbonitrides, oxides, and oxycarbonitrides of molybdenum silicide (MoSi); Nitrides, oxides, carbides, oxynitrides, carbonitrides, oxycarbides and oxycarbonitrides of tantalum silicide (TaSi); Nitride, oxide, carbide, oxynitride, carbonitride, oxycarbide, and oxycarbonitride of tungsten silicide (WSi) are formed of a nitride, an oxide, a carbide, an oxynitride, a carbonitride, an oxycarbide and an oxide carbonitride of titanium silicide Available.

The thickness of such a light-shielding film may be 500 to 2000 Å, more preferably 800 to 1500 Å, and further preferably 900 to 1400 Å.

In the optical film 12 described above, the presence of a metal other than Cr is not excluded, but it is not necessary to include other metals such as Mo and Si. Preferably, the optical film 12 is a film made of a Cr or Cr compound.

The optical film 12 described above is formed by a known means such as a sputtering method. Preferably, a means is employed in which the film composition becomes substantially uniform. Here, the substantially uniformity means that, with the object of imparting a stepwise or continuous compositional change in the film thickness direction, without the step of supplying the sputtering material or the sputtering gas or changing the supply amount during the film forming step, It means to do the tabernacle.

<Modification Process>

The film quality of the optical film 12 is modified by preparing a photomask intermediate having the optical film 12 on the transparent substrate 11 and irradiating the optical film 12 with vacuum ultraviolet rays )].

The vacuum ultraviolet ray (hereinafter, also referred to as VUV) refers to a light having a shorter wavelength in ultraviolet rays, and is mainly attenuated by absorption in the atmosphere, but is known to be capable of preventing attenuation in vacuum. In the present invention, a vacuum ultraviolet ray refers to an ultraviolet ray having a wavelength of 10 to 200 nm and preferably has a wavelength of 100 to 200 nm. For example, excimer light having a wavelength of 126 nm (argon), 146 nm (krypton) and 172 nm (xenon) can be mentioned. In the present invention, it is preferable to use xenon excimer light of 172 nm.

The film quality modification of the optical film 12 by this VUV irradiation is performed with respect to the inside of the optical film 12 and more specifically when the thickness thereof is T, the surface of the optical film 12 The surface on the side opposite to the side closer to the substrate 11) is at least T / 3 in the thickness direction. By performing such a modification, it becomes possible to make the end face of the edge portion of the optical film pattern formed by the optical film 12 closer to the surface of the transparent substrate 11 perpendicularly as described later. This makes it possible to increase the precision of line width control (CD control) of the transfer pattern to be transferred using the photomask.

More specifically, the above-mentioned modification of the film quality is intended to change the etching property when the optical film 12 is wet-etched, which has a modification effect not only on the surface of the optical film 12 but also on the inside thereof. Preferably, the wet etching property of the inside of the optical film at least at a depth of T / 3 or more in the thickness direction from the surface is changed before the modification.

More specifically, the wet etching speed of the optical film in the optical film is changed before the modification. The wet etching will be described later in &quot; an etching step and a resist pattern removing step &quot;.

The film quality of the optical film 12 can be modified by the VUV irradiation as described above and the behavior in the wet etching is changed because the film density changes within the irradiated optical film 12 .

In the present invention, film reforming is performed by subjecting the optical film 12 to VUV irradiation as described above. In this modification of the film, not only the surface of the film but also the inside of the film is required to have a modifying effect by the predetermined depth as described above. This is because it is desired to influence the etching behavior in the etching process of the optical film 12 by the modification.

As a more preferable form, another modification effect can be generated by the depth in the optical film 12 by VUV irradiation. For example, the film density of the optical film 12 can be increased. Further, by irradiating from the surface side of the optical film 12, the following modification can be performed. That is, in the vicinity of the surface of the optical film 12, the film density is increased more than before the modification, and the depth of the portion closer to the surface (the inner portion of the optical film 12, , The film density can be made higher than that of the transparent substrate 11 (the portion closer to the transparent substrate 11). Further, for example, the film density of the portion near the surface of the optical film 12 may be higher than the film density near the back surface. Further, at a portion deeper than the vicinity of the surface, the film density may be changed to be lower than before the reforming.

In the present invention, the irradiation conditions of the vacuum ultraviolet ray are preferably as follows. The irradiation atmosphere is not particularly limited and can be an inert gas atmosphere such as nitrogen or a vacuum, but the effect of the present invention can be sufficiently obtained even in the atmosphere. However, in the case of the atmosphere, it is preferable to reduce the distance between the irradiation device and the irradiated object (optical film 12) in consideration of the attenuation factor of the vacuum ultraviolet ray.

As the irradiation energy of the vacuum ultraviolet ray, it is essential to make sufficient energy for the modification of the optical film 12. For example, 20 J / cm 2 or more, preferably 30 J / cm 2 or more, and more preferably 40 J / cm 2 or more with respect to the optical film 12. The irradiation energy is preferably 60 J / cm 2 or less from the viewpoint of irradiation efficiency.

When the optical film 12 is subjected to such VUV irradiation, a light source with an illuminance of 30 to 50 mW / cm 2 is used, and the optical film 12 is irradiated for 20 minutes or more (total time when a plurality of irradiation is performed) Can be done.

Further, since the vacuum ultraviolet rays are soaked by the distance between the light source and the irradiated object and the medium existing therebetween, an effective irradiation amount is determined in consideration of the attenuation factor. The irradiation energy is as described above, but may be in the range of 30 to 50 J / cm 2, more preferably 40 to 50 J / cm 2. For example, in a light source with an illuminance of 40 mW / cm &lt; 2 &gt;, if the decay rate is 70%, irradiation energy of 45 J / cm &lt; 2 &gt; Here, the damping factor refers to the amount of residual after attenuation with respect to the irradiation amount of the irradiation device. The decay rate is preferably 60% or more.

It is preferable that the VUV irradiation is performed from the surface side of the optical film 12 (the surface side opposite to the surface facing the transparent substrate 11). This makes it possible to advantageously perform the asymmetric modification in the thickness direction of the optical film 12 described above.

In the production of a photomask, usually, cleaning is carried out for various steps that have been subjected to the process. However, in the case where there is a cleaning step (including sulfuric acid cleaning) using an acid after VUV irradiation, The effect of the invention is remarkable. The optical film 12 subjected to the modification treatment according to the present invention has a suppressed change in the surface reflectance caused by the cleaning process as described later, whereby the CD control in the surface of the transfer pattern is precisely and precisely I can do it.

In the reforming step, the optical film 12 may be subjected to heat treatment with the above-described VUV irradiation (or after the VUV irradiation). However, the effect of the present invention can be obtained even when heating is not performed at a high temperature (for example, 200 degrees or more).

&Lt; Resist Coating Step and Resist Pattern Forming Step &

A photoresist is applied on the optical film 12 modified in the above-described &quot; reforming step &quot; to form a photoresist film 13 (Fig. 4 (d)). The photoresist film 13 may be formed by applying a photoresist directly onto the entire surface of the optical film 12 after the modification process and may be formed by forming another film pattern formed on at least a part of the optical film 12 after the modification process Or by applying a photoresist.

The desired resist pattern 13a can be formed by drawing and developing the photoresist film 13 formed in this way by a known appropriate exposure apparatus (Fig. 4 (e)).

&Lt; Etching process and resist pattern removal process >

A resist pattern 13a made of photoresist is formed on the optical film 12 and then etching is performed using the resist pattern 13a as a mask. Thus, the exposed portion of the optical film 12 that is not covered with the resist pattern 13a is removed to form the optical film pattern 12a (Fig. 4 (f)).

For removal (patterning) of the exposed portion of the optical film 12, wet etching using an etching liquid is applied. Wet etching is likely to be isotropic etching tendency and side etching of the etched film proceeds more easily than dry etching (using an etching gas). However, it is advantageous in that it is not necessary to make the atmosphere vacuum when patterning a large area such as a photomask for a display device. Therefore, the method of manufacturing a photomask of the present invention is suitably used for manufacturing a photomask for a display device.

1, the chrome phase shift film formed on the transparent glass substrate 101 is subjected to wet etching using the resist pattern 103 of the positive type photoresist as a mask. As a result, The end portion of the cross section is not perpendicular to the surface of the transparent glass substrate 101 but becomes a shape that is largely inclined.

However, in the present invention, the film quality of the optical film 12 is suitably modified, and the end portion of the end face of the optical film pattern 12a is perpendicular to the surface of the transparent substrate 11 close. Specifically, the angle of the etched surface of the optical film 12 is preferably 50 to 90 degrees by the etching process.

The angle of the etched cross section is defined as follows with reference to Fig. When the thickness of the optical film 12 is T in the cross section of the portion to be etched of the optical film 12, the optical film 12 has a T value of 10 from the surface facing the transparent substrate 11 to the surface side, And an auxiliary line parallel to the surface of the transparent substrate 11 is drawn on a portion of the optical film 12 that has been raised by 10% and a portion of the optical film 12 which is lowered by 10% from the surface side of the transparent substrate 11 toward the surface thereof. A straight line connecting the two auxiliary lines to the intersection of the sides corresponding to the etched end face is drawn and the angle (section angle?) Formed by the straight line with the surface of the transparent substrate 11 is defined as the angle of the etched section do. In the present invention, this angle is preferably 50 to 90 degrees, more preferably 70 to 90 degrees as described above.

After the optical film pattern 12a is formed by the etching process described above, the photomask 10 is manufactured by removing the resist pattern 13a by various conventionally known methods (Fig. 4 (g)).

The optical film 12 described above may be a light-shielding film or a phase shift film. In the present invention, as described above, since the angle of the etched end face of the optical film 12 is 90 degrees (that is, perpendicular to the surface of the transparent substrate 11) or a value close thereto, And can be done in detail. When the optical film 12 is a phase shift film, the contrast in the light intensity distribution of the transmitted light is improved by the phase inversion of the transmitted light at the edge of the phase shift film. Therefore, by using the photomask 10 manufactured by the method of manufacturing a photomask of the present invention, it is possible to stably form the pattern on the transferred body even if the CD is a fine pattern of less than 3 mu m, The CD fluctuation in the surface of the photomask is sufficiently suppressed by the cleaning resistance of the optical film 12. [

In addition, in the method for manufacturing a photomask of the present invention, various steps other than the film forming step, the reforming step, the resist applying step, the resist pattern forming step, the etching step, and the resist pattern removing step described above may be performed. For example, the cleaning process may be performed when the operation of each of these processes is completed, or another process of forming a film described later may be performed.

In the conventional cleaning process, when the optical film 12 is on the outermost surface, that is, when there is a possibility of coming into contact with the cleaning liquid, it is completely inevitable to receive damage by the cleaning liquid. In particular, the Cr-based optical film is susceptible to damage by acid cleaning such as sulfuric acid. The following problems may be caused by this damage.

For example, in the case where the optical film is a phase shift film, there is a risk that the phase shift amount is changed due to the film thickness being smaller than the original design value, and this shift amount change is particularly So that it occurs non-uniformly in the plane. As a result, the light intensity distribution of the exposure light formed on the transferred body is disturbed, and the line width CD tends to be uneven.

Further, when the optical film is a phase shift film or a light-shielding film, the surface reflectance rises above the initial value and becomes nonuniform within the plane of the photomask. For example, the reflectance with respect to the imaging light affects the generation of a standing wave to be applied to the photoresist on the optical film at the time of conversation, so that the shape of the cross section of the resist pattern is made non-uniform. It goes without saying that this uneven resist pattern affects CD control when the optical film is etched.

According to the present invention, since the optical film 12 is improved in washing resistance by modification, when the optical film 12 is cleaned after film formation and modification (even in the case of using a cleaning liquid containing an acid) The change of the surface reflectance can be reduced.

For example, in the present invention, the amount of change in reflectance of the optical film 12 with respect to light having a wavelength of 413 nm by cleaning can be suppressed to 3% or less. Here, the reflectance change amount is defined as follows. The surface reflectance at an arbitrary position on the transparent substrate (Reference) having the optical film in the state where the cleaning process is not performed after the optical film 12 is formed (the state before the irradiation even in the sample subjected to the VUV irradiation) (After the irradiation for the sample subjected to the VUV irradiation), the surface reflectance at the same position after the cleaning of the transparent substrate having the optical film by the cleaning liquid containing H ₂ SO ₄ as β% (%) Is the reflectance change amount.

[Other Forms of Photomask Manufacturing Method]

Hereinafter, another embodiment of the method of manufacturing the photomask of the present invention will be described with reference to FIG. In Fig. 6, the same film and pattern are denoted by the same reference numerals, and the other denotations are omitted.

6, a photomask intermediate having a light-shielding film 14 on a transparent substrate 11 is first prepared (Fig. 6 (b)). The photomask intermediate may be, for example, a photomask blank obtained by preparing a transparent substrate 11 (FIG. 6A) and forming a light-shielding film 14 thereon (FIG. 6B) . Subsequently, a resist film 15 is applied on the light-shielding film 14 (Fig. 6 (c)), and a resist pattern 15a is formed on the light-shielding film 14 by drawing and development d)].

The resist pattern 15a is removed (Fig. 6 (f)) after the light-shielding film 14a is formed by etching the light-shielding film 14 using the resist pattern 15a as a mask ]do. The optical film 12 is then formed on the light-shielding film pattern 14a and the exposed portion of the transparent substrate 11 (laminated intermediate, Fig. 6 (g)).

Then, the optical film is subjected to VUV irradiation to modify the film quality (Fig. 6 (h)) and the photoresist is coated on the optical film 12 to form the photoresist film 13 (Fig. 6 (i)), and the resist pattern 13a is formed by imaging and developing it (Fig. 6 (j)). The optical film 12 is wet etched using the resist pattern 13a formed thereon as a mask to form the optical film pattern 12a (Fig. 6 (k)), and the resist pattern 13a is subsequently removed, The photomask 10 is completed (Fig. 6 (1)).

Also in the above-described method of manufacturing the photomask in the embodiment of FIG. 6, it is possible to appropriately perform other steps such as a cleaning step and a film forming step.

Since the optical film in the present invention can be a light-shielding film, it is also possible to consider the light-shielding film pattern 14a and the optical film 12 in the form of Fig. 6 as an optical film in the manufacturing method of the photomask of the present invention Do.

[Photomask]

The present invention also relates to a photomask having a specific structure, and this photomask is typically manufactured by the above-described method for producing a photomask of the present invention. Hereinafter, the photomask of the present invention will be described with reference to cross-sectional views of the photomask of the present invention shown in Figs. 7 (c) and 7 (d).

A photomask 10 of the present invention is a photomask having a transfer pattern including an optical film pattern 12a formed by patterning by wet etching an optical film containing Cr formed on a transparent substrate 11 , Preferably, the angle of the etched end face of the optical film is from 50 degrees to 90 degrees.

For example, by performing the film modification of the optical film by the VUV irradiation described in the manufacturing method of the photomask of the present invention, the angle of the etched end face of the optical film is set so as to be substantially perpendicular to the surface of the transparent substrate 11, The pattern 12a can be obtained. Further, by the above-mentioned film reforming, the resistance to cleaning of the optical film is increased, and the damage due to frequent cleaning (including pickling) in the production of a photomask is suppressed, and the reflectance Is small. By the presence of the optical film pattern 12a formed of such an optical film, formation of the fine pattern on the transferred body can be stably performed by using the photomask 10 of the present invention. In particular, It is possible to accurately transfer a fine pattern uniformly and stably to the transferred object in the plane.

The transparent substrate 11 and the optical film are as described for the production method of the photomask of the present invention, and the optical film can be formed of various materials containing Cr and can be a phase shift film or a light shielding film.

In particular, in the photomask 10 of the present invention, it is preferable that the optical film is a phase shift film which shifts the phase of the representative wavelength of the exposure light by approximately 180 degrees. According to the present invention, the accuracy of transfer of the optical film pattern 12a can be further improved by making the optical film pattern 12a finer and more accurate and exhibiting the effect of improving the contrast by the phase shift film. As described above, in the present invention, although the angle of the etched surface of the optical film is close to the perpendicular to the surface of the transparent substrate, excellent transferability in the case where the surface to be etched of the phase shift film has such a shape is described in the simulation As described above.

In the present invention, the exposure light is light obtained by a light source employed in an LCD exposure apparatus, and includes any one of i-line (365 nm), h-line (405 nm), and g- Light may be used, and more preferably all of them may be used. In the present invention, either one of them is a representative wavelength, and the transmittance and the phase difference (or the phase shift amount) are defined.

Although the phase shift film shifts the phase of the representative wavelength of the exposure light by approximately 180 degrees, it partially transmits the exposure light (specifically, the transmittance to the representative wavelength of the exposure light is 2 to 30% Is preferably 3 to 20%, more preferably 3 to 10%), and shifts the phase of the representative wavelength of the exposure light by approximately 180 degrees. Also, it is approximately 180 degrees, 120 degrees to 240 degrees, preferably 150 to 210 degrees.

The phase shift film shifts the phase of the representative wavelength of the exposure light by approximately 180 degrees, and the representative wavelength is any one of i-line (365 nm), h-line (405 nm) and g-line (436 nm). In the present invention, the difference in the amount of phase shift for each of these light beams of the phase shift film can be set to 20 degrees or less (more preferably 10 degrees or less), and in this case, desirable.

The difference in the exposure light transmittance for these three wavelengths is also within 5% (when the transmittance for each wavelength is X%, Y%, and Z%, the difference between X, Y, 5%), and more preferably 2% or less.

As described above, in the photomask of the present invention, the optical film may be a light-shielding film, but an antireflection film may be formed on the light-shielding film. As a material for forming the antireflection film, a Cr compound (for example, CrO) can be mentioned.

The photomask 10 of the present invention essentially has a transfer pattern including the above-described transparent substrate 11 and an optical film pattern 12a formed by patterning the optical film formed thereon by wet etching. In the photomask of the present invention, other film or film pattern may be added in addition to these constituent elements as long as the effect of the present invention is not hindered.

<Transmissive part, phase shift part, shielding part>

The photomask of the present invention has a transfer pattern on a transparent substrate. This transfer pattern may have the following parts.

That is, a portion where the surface of the transparent substrate is exposed can function as a transparent portion. Further, the phase shift film as the optical film is formed on the transparent substrate, so that the phase of the exposure light can be shifted by about 180 degrees in this portion. This portion can function as a phase shift portion. Further, when the light shielding film as the optical film and / or another film having substantially the light shielding property are formed on the transparent substrate so that the exposure light is shielded (for example, optical density OD? 3 or more) Function.

[First Photo Mask]

Next, a first photomask exemplified as a photomask of the present invention will be described with reference to FIG. The first photomask is a photomask having a line-and-space pattern or a hole pattern, in which an optical film pattern 12a is formed on a transparent substrate 11.

FIG. 7A is a top view of a line-and-space pattern, and FIG. 7C is a cross-sectional view of a portion indicated by a chain line in FIG. 7A. FIG. 7B is a top view of the hole pattern, and FIG. 7D is a cross-sectional view of a portion indicated by a one-dot chain line in FIG. 7B.

The optical film forming the optical film pattern 12a may be a light-shielding film or a phase shift film. The portion where the light shielding film is formed as the optical film functions as the light shielding portion 17 and the portion where the phase shift film is formed as the optical film functions as the phase shift portion 17. [ The exposed portion of the transparent substrate 11, which is not covered with the optical film pattern 12a, constitutes the transparent portion 16.

In this transfer pattern, when the optical film is a phase shift film, light having a substantially inverted phase is generated at the boundary between the adjacent transparent portion 16 and the phase shifting portion 17, An effect of increasing the depth (also referred to as a phase shift effect) is obtained.

[Second photomask]

Next, a second photomask exemplified as another embodiment of the photomask of the present invention will be described with reference to FIG. The second photomask is also a photomask having a line-and-space pattern or a hole pattern.

FIG. 8A is a top view of the line-and-space pattern, and FIG. 8C is a cross-sectional view of a portion indicated by a chain line in FIG. 8A. 8 (b) is a top view of the hole pattern, and FIG. 8 (d) is a cross-sectional view of a portion indicated by a chain line in FIG. 8 (b).

In the second photomask, an optical film pattern 12a made of a phase shift film is formed on a photomask intermediate body on which a light-shielding film pattern 14a is formed on a transparent substrate 11. [

The portion where the light shielding film pattern 14a is present constitutes the shielding portion 19 and the portion where only the phase shift film pattern 12a is formed constitutes the phase shift portion 18, The exposed portion constitutes the transparent portion 16.

In any of the above-described first and second photomasks, the phase shift film or the light-shielding film as an optical film has a portion (etched section) where the film surface is exposed by etching. In the present invention, for example, by subjecting an optical film to VUV irradiation and modifying the film quality thereof, the etched end face of the optical film is nearly perpendicular to the surface of the transparent substrate. Thus, when the photomask of the present invention is used, the transferability of a fine transfer pattern is improved.

[Use of photomask of the present invention]

There is no particular limitation on the use of the photomask of the present invention described above. For example, when the photomask of the present invention is used as a phase shift mask, it can be suitably used as a transfer mask including a line-and-space pattern for forming a pixel electrode or the like of a display device.

As described above, by using the photomask of the present invention as described above, a fine transfer pattern can be transferred accurately to the transferred body. Furthermore, since the optical film pattern constituting the photomask has high resistance to pickling, Also as the mask, it is possible to uniformly transfer the transfer pattern in the plane.

Therefore, the photomask of the present invention can be a photomask for manufacturing a display FPD (flat panel display) including an LCD (liquid crystal display). The photomask of the present invention can be used as a photomask for exposure by, for example, i-line (365 nm), h-line (405 nm), or g-line (436 nm) The transmittance and the phase shift amount can be defined as the representative wavelength. The photomask of the present invention is also preferable from the viewpoint of exposure efficiency by using a light source including a wavelength region of 365 to 436 nm including all of these wavelengths.

The present invention includes performing the pattern transfer by using the photomask and using exposure light having a wavelength range of 365 to 436 nm.

The exposure apparatus used for pattern transfer can be a standard exposure apparatus for FPD or LCD for a standardized exposure. That is, by using a light source of a wavelength range including an i-line, an h-line, and a g-line (also referred to as a broad wavelength light source), a sufficient irradiation light amount can be obtained. However, only light of a specific wavelength (for example, i-line) may be used by using an optical filter.

The optical system of the exposure apparatus may have a numerical aperture NA of 0.06 to 0.10 and a Coherence factor sigma of 0.5 to 1.0.

Of course, the present invention can also be applied to the case of transfer using a wider range of exposure apparatuses. For example, the NA may be in the range of 0.06 to 0.14, or 0.06 to 0.15. A high-resolution exposure apparatus having an NA of more than 0.08 is required, and the present invention can be applied to these.

[Example]

[First embodiment and first comparative example]

A photomask blank in which a light-shielding film made of CrN / CrC / CrON having an antireflection layer on its surface was formed as a Cr-based optical film on a transparent substrate (size 330 mm x 450 mm) by a sputtering method was prepared. The film thickness of the optical film was 1350 Å. This is called Reference.

The optical film of this photomask blank was subjected to VUV irradiation. More specifically, irradiation with an irradiation energy of 45 J / cm 2 was performed on the surface of the optical film by using an irradiation device for irradiating 40 mW / cm 2 of xenon excimer light (wavelength: 172 nm). Thereafter, the photomask blank was rinsed with an aqueous H ₂ SO ₄ solution.

For the sake of comparison, the same reference photomask blank was also subjected to the same cleaning treatment as above except that the VUV irradiation was not performed.

The optical reflectance of the surface of these two photomask blankes (the photomask blank of the first embodiment and the first comparative example) was measured and compared with the measurement result of Reference. The results are shown in Fig.

As is clear from Fig. 9, in the first embodiment, the difference in reflectance between the reference and the reference is small in almost the entire region of the wavelength of 350 nm or more. The amount of change in the reflectance with respect to the wavelength 413 nm was 4.4% in the first comparative example (FIG. 9A) and 2.5% in the first embodiment (FIG. 9B).

This result can suppress the change in the reflectance. In the first embodiment, therefore, the reflectance variation in the entire plane becomes small, and the pattern formation accuracy of the photomask manufactured using this photomask blank The controllability of the catalyst is very high.

[Second embodiment and second comparative example]

A phase shift film made of chromium oxide was formed on a transparent substrate (size: 330 mm x 450 mm) by sputtering. The film thickness of the phase shift film was set to 1250 ANGSTROM. The transmittance of the phase shift film to the i-line was 6% and the phase shift amount was 180 degrees.

The phase shift mask blank was subjected to a VUV irradiation process in the same manner as in the first embodiment, and was cleaned in the same manner as in the first embodiment. The optical reflectance in the plane after cleaning exhibited the same tendency as in the first embodiment. Thereafter, a positive-type photoresist film having a thickness of 8000 ANGSTROM was applied on the phase shift film.

Next, a photomask blank having a resist was set in a drawing apparatus and laser drawing (413 nm) was performed to draw a line-and-space pattern (line width 3 m, space width 3 m) and developed. Subsequently, the phase shift film was wet-etched using the formed resist pattern as a mask. As the etchant, ceric ammonium nitrate was used. This is referred to as a patterned sample of the second embodiment.

A patterning sample of the second comparative example formed in the same manner as above was prepared except that the above VUV irradiation was not performed for comparison.

SEM photographs of etched sections of the phase shift film are shown in FIGS. 1A and 1B, respectively, for the patterned samples of the second comparative example and the second embodiment.

In the second comparative example, the tapered lower side length A is 150 nm, whereas in the second embodiment, it is 20 nm, and the etched end face is formed almost perpendicular to the transparent substrate surface.

In the second comparative example, the etching cross-section angle (according to the definition in Fig. 5) was measured. In contrast, in the second comparative example, 80 degrees (90 degrees at the resist interface side and 50 degrees at the transparent substrate interface side) Respectively.

For the photomask blank subjected to the VUV irradiation process and the photomask blank not subjected to the VUV irradiation process similar to those of the second embodiment, the film density of the phase shift film was measured by the XRR method XRR. The results are shown in Fig. Here, not only near the surface of the film but also inside the film (a portion at a depth of 1/3 or more of the film thickness from the film surface to the depth) has a change in film density. Particularly, there is a portion where the film density is decreased in the inside of the film (in the present embodiment, a portion at a depth of 1/3 or more of the film thickness in the depth direction from the film surface), and a portion in the vicinity of the film surface 10% or less), there was a portion where the film density increased.

Such a tendency of the film density is connected to the occurrence of an etching behavior that the etching rate inside the film is faster than the etching rate in the vicinity of the film surface. This is because the inclination of the etching end face as shown in Fig. And is well matched with the phenomenon suppressed by the present invention.

For example, the film-forming material can be changed stepwise or continuously by changing the material (etching gas, sputtering target) to be supplied in the thickness direction of the film in the process of forming the etched film by the sputtering method or the like. Thus, it is also possible to change the density in the observed phase shift film (optical film).

In this case, however, it is not easy to establish a film forming process for obtaining the target etching property, and the etching behavior of the etched film by the established film forming process is different from that of the original film. As a result, it is necessary to re-establish the entirety of the patterning condition including the etching condition.

According to the present invention, by adjusting the irradiation condition of the VUV, modification of the etched film can be performed relatively freely, and there is no great change in the behavior at the time of patterning, so that it is very significant in the actual production process.

The photomask of the present invention has the etched cross section of the optical film pattern close to the perpendicular to the surface of the transparent substrate so that the profile of the photoresist pattern shape on the surface to be obtained by exposure can be improved, The light reflectance of the film surface can be stably controlled. As a result, the photomask of the present invention can be uniformly transferred within the plane even if the fine pattern is precisely formed and the photomask is large. Therefore, the photomask is suitable as a photomask for producing a display device.

10: Photomask
11: transparent substrate
12: Optical film
12a: Optical film pattern
13: Photoresist film
13a: Resist pattern
14:
14a: a light-shielding film pattern
15: resist film
15a: resist pattern
16:
17: phase shifting portion or shielding portion
18: phase shift unit
19: Light shield

Claims (11)

A manufacturing method of a photomask having a transfer pattern including an optical film pattern formed by patterning an optical film containing Cr on a transparent substrate,
Preparing a photomask intermediate having the optical film on the transparent substrate;
A modifying step of modifying the film quality of the optical film by irradiating the optical film with vacuum ultraviolet light;
A step of applying a photoresist film on the optical film after the modification,
A step of forming a resist pattern on the photoresist film by performing drawing and development,
An etching step of wet-etching the optical film using the resist pattern to form the optical film pattern;
And removing the resist pattern,
In the step of modifying the optical film, the wet etching property of the optical film is modified with respect to the inside of the optical film
A method of manufacturing a photomask. The method according to claim 1,
Wherein the photomask intermediate is a photomask blank in which at least the optical film is formed on the transparent substrate. The method according to claim 1,
Wherein the photomask intermediate is a laminated intermediate in which a film pattern is formed on the transparent substrate and at least the optical film is formed. 4. The method according to any one of claims 1 to 3,
Wherein the optical film is modified so that the wet etching property of the optical film is changed with respect to the inside of the optical film at least T / 3 in the thickness direction from the surface when the thickness of the optical film is T A method of manufacturing a photomask. 4. The method according to any one of claims 1 to 3,
Wherein an angle of an etched end face of the optical film is set to 50 to 90 degrees by the etching process. 4. The method according to any one of claims 1 to 3,
Wherein the optical film is a phase shift film that shifts a phase of a representative wavelength of exposure light for exposing the photomask by about 180 degrees. 4. The method according to any one of claims 1 to 3,
Wherein the photomask includes a transparent portion in which the surface of the transparent substrate is exposed and a phase shifting portion in which a phase shift film that partially transmits the exposure light and shifts the phase of the representative wavelength of the exposure light by approximately 180 degrees And the optical film is the phase shift film. 4. The method according to any one of claims 1 to 3,
Wherein the photomask is a photomask for manufacturing a display device exposed using exposure light having a wavelength range of 365 to 436 nm. 1. A photomask having a transfer pattern comprising an optical film pattern formed by patterning by wet etching, wherein an optical film containing Cr formed on a transparent substrate is patterned by wet etching,
When the thickness of the optical film is T, the film is reformed inside the optical film at least at a depth of T / 3 or more in the thickness direction from the surface,
Wherein an angle of the etched end face of the optical film is from 50 degrees to 90 degrees. 10. The method of claim 9,
Wherein the optical film is a phase shift film for shifting the phase of the representative wavelength of the exposure light by approximately 180 degrees. A pattern transfer method characterized by using a photomask as set forth in any one of claims 9 to 10 as a pattern transfer method, wherein pattern transfer is performed using exposure light having a wavelength range of 365 to 436 nm.

Images