JP2019101220A - Photomask substrate, photomask and method of manufacturing photomask - Google Patents

Abstract

To provide a photomask substrate that enables a fine pattern to be formed by wet etching with high accuracy, a photomask, and a method of manufacturing a photomask.SOLUTION: A photomask substrate 2 comprises: a transparent substrate 10; a semi-transmissive layer 20 formed on the transparent substrate 10 and having semi-transmissive properties to irradiation light; a light shielding layer 33 formed on the semi-transmissive layer 20 and substantially shielding irradiation light; and an antireflection layer 35 formed on the light shielding layer and preventing reflection of irradiation light. The semi-transmissive layer 20 contains a chromium nitride or a chromium oxide as the main component. The light shielding layer 33 contains titanium metal as the main component. The antireflection layer 35 contains a titanium oxynitride as the main component.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a photomask substrate having a semitransparent layer, a photomask and a method of manufacturing the photomask, and in particular, fine patterning of an LSI or the like, a display element of a flat panel display such as LCD, PDP, or EL, A photomask substrate for forming a pattern, a photomask, and a photomask for use in surface modification such as an antireflection plate using fine scattering irregularities, a diffuse reflecting plate with or without fine particles, a microlens array, and other array irregularities, etc. It relates to the manufacturing method.

With the development of liquid crystal display elements (reflective, transmissive and semi-transmissive), plasma display elements, organic EL (electroluminescent) display elements, and other flat panel display elements, the size of production sites for these display elements , Various patterns of photo masks are used.
For example, in a TFT (Thin Film Transistor) manufacturing process in forming a liquid crystal display element, although depending on the manufacturing method, generally, about three to five different patterning photomasks are required. In addition, on the side of the color filter disposed to face the liquid crystal display element, a photomask corresponding to the liquid crystal display element for forming a black matrix and for forming a colored layer is required.

  In photomasks used to form fine patterns such as LSI, halftone masks are used for the purpose of improving the pattern accuracy (for example, Patent Documents 1 to 9). The halftone mask is a photomask in which a semi-transmissive layer (halftone) is formed between the transmitting portion and the light shielding portion. The film thickness of the semi-transmissive layer is designed to invert the phase by λ / 2 or shift the phase by ± λ / 4 in accordance with the exposure wavelength to be used. This prevents diffraction of light generated between adjacent patterns, and makes the light intensity difference clear between the edge portion of the light shielding portion and the transmitting portion of the mask. In addition, since moire and halation are less likely to occur, resolution can be improved. In addition, there is also a method (grey tone mask) for obtaining the same effect as halftone by forming a fine continuous stripe pattern.

  As a method of manufacturing such a photomask with a halftone, a resist is coated on a photomask substrate (blank for photomask) on which a first layer (semi-transmissive layer or light shielding layer) is formed first, and exposed. After patterning once, the resist is removed and washed, and a second layer (a light shielding layer or a semitransparent layer) is formed again using a vacuum device or the like, and then a second process is performed by a photolithography step Methods of patterning two layers are known (see, for example, Patent Documents 3 and 9). As another manufacturing method, a method is also known in which a thin film having a homogeneous or heterogeneous multilayer structure is first formed and then each pattern is formed by dry etching (for example, Patent Documents 2 and 5).

JP 7-209849 A Unexamined-Japanese-Patent No. 9-127677 gazette Japanese Patent Laid-Open No. 2001-27801 JP 2001-83687 A Japanese Patent Application Laid-Open No. 2001-132043 Unexamined-Japanese-Patent No. 2003-29393 Unexamined-Japanese-Patent No. 2003-322949 Unexamined-Japanese-Patent No. 2004-29746 JP, 2006-18001, A

  In the conventional method, it is necessary to perform patterning on the first layer formed using a vacuum device or the like, and then perform film formation on the second layer using the vacuum device or the like to perform patterning. Because of this, it is necessary to perform the film formation process using a vacuum device or the like at least twice. For this reason, many processes are required to manufacture a photomask, and there is a disadvantage that the manufacturing cost is increased.

  Also, in general, for pattern formation of a photomask, dry etching in which a layer on a photomask substrate is irradiated with ions by plasma such as reactive gas or laser light to perform etching, and corrosive etching solution (chemical solution) There are two types of etching methods, wet etching (also referred to as wet etching) that chemically corrodes the layer. Among these, dry etching is generally used to form a photomask pattern.

  However, dry etching has various technical problems associated with the increase in size and mass production of photomasks. For example, in the direct drawing process in dry etching, since the drawing area increases with the increase in size of the photomask, the drawing time by electron beam, laser or the like increases, and the tact time of photomask manufacturing can be improved. It was difficult. In addition, with the increase in size of the photomask, it is also necessary to increase the size of equipment such as a vacuum tank and a gas type switching device, which increases the burden on the equipment and increases the cost required for manufacturing the photomask. There was also a disadvantage. Furthermore, since the number of substrates that can be processed at one time is limited, it is not suitable for mass production.

On the other hand, in wet etching, equipment and etching solutions are generally inexpensive, and pattern formation by etching can be performed in a shorter time than dry etching. It is convenient for mass production and production in a short time.
However, in wet etching, when etching one of the stacked layers, a part of the other layer is dissolved, or another layer is formed by the interface between the other layer and the etching solution or grain boundary. The reaction between the substance and the etching solution to change the structure to a chemically different structure may cause damage to other layers, which makes it difficult to perform high-precision microfabrication. In particular, when manufacturing a mask in which different types of layers are stacked, such as a halftone mask in which a phase shift layer and a light shielding layer are stacked, selectively etching only a target layer without damaging other layers. Was technically difficult.

In view of the above problems, it is an object of the present invention to form a photomask capable of forming two kinds of fine patterns on a surface of a transparent substrate in a short time and at a low cost by a wet etching method which has been difficult with conventional photomask manufacturing technology. It is to provide a substrate.
Another object of the present invention is to provide a photomask having two kinds of fine patterns formed in a short time and at low cost by sequentially etching a photomask substrate by wet etching, and a method of manufacturing the same. It is in.

  According to the photomask substrate of the present invention, the above object is achieved by a transparent substrate, a semi-transmissive layer formed on the transparent substrate and having translucency for irradiated light, and the radiation formed on the semi-transmissive layer. A photomask substrate comprising: a light shielding layer for shielding light; and an antireflective layer formed on the light shielding layer to prevent reflection of irradiation light, wherein the semitransparent layer is made of chromium nitride or chromium oxide. The light-shielding layer is a layer containing titanium metal as the main component, and the anti-reflection layer is a layer containing titanium oxynitride as the main component. Resolved.

Titanium and titanium oxynitride are readily soluble in a mixture of potassium hydroxide, hydrogen peroxide and water, which is the first etching solution, and cerium ammonium nitrate, perchloric acid, and the second etching solution. It is insoluble or poorly soluble in water mixtures.
On the other hand, chromium nitride and chromium oxide are insoluble or poorly soluble in a mixture of potassium hydroxide, hydrogen peroxide and water as a first etching solution, and cerium ammonium nitrate as a second etching solution. It is readily soluble in a mixture of perchloric acid and water.
Therefore, according to the photomask substrate of the present invention, selectivity to each etching solution is improved by employing chromium nitride or chromium oxide as the semi-transmissive layer, titanium as the light shielding layer, and titanium oxynitride as the antireflective layer. It is possible to form a more accurate and finer pattern.

Specifically, the light shielding layer and the antireflective layer can be selectively etched using the first etching solution, and the semi-transmissive layer can be selectively etched using the second etching solution.
Then, each layer is selectively etched with a different etching solution to form two types of patterns of a semi-transmissive pattern and a light-shielding pattern on a transparent substrate, and a light-shielding portion where the light-shielding pattern is exposed and a semi-transmissive pattern on the surface It becomes possible to form three areas of the exposed semi-transmissive portion and the transparent portion where the transparent substrate is exposed on the surface by wet etching using an etching solution.

  As described above, in the photomask substrate of the present invention, each layer has resistance to different etching solutions, and the second etching solution that solubilizes the semi-transmissive layer by utilizing this difference in resistance. The light shielding layer and the antireflective layer are hardly reformed or damaged, and conversely, the semi-transmissive layer is hardly reformed or damaged by the first etching solution that solubilizes the light shielding layer and the antireflective layer Absent. For this reason, it becomes possible to manufacture a photomask with high precision and a fine pattern formed thereon.

Further, by providing the anti-reflection layer, an anti-reflection effect can be obtained, and halation and the like due to reflection of the irradiation light at the time of mask exposure can be prevented.
In addition, the light shielding layer and the antireflective layer can be etched at once, and the light shielding pattern having the antireflective layer pattern formed on the surface can be easily formed.

  Furthermore, since the anti-reflection layer is formed of a layer mainly composed of titanium oxynitride having a low reflectance, a high anti-reflection effect can be obtained, and halation due to reflection of irradiation light during mask exposure can be prevented. Because it is preferable.

At this time, it is preferable that the difference between the maximum value and the initial value of the transmittance of the semi-transmissive layer in a wavelength range of 350 nm to 450 nm is within 10%.
When the semi-transmissive layer is a layer mainly composed of chromium nitride or chromium oxide, the difference between the maximum value and the initial value of the transmittance is within 10% in the wavelength range of 350 nm to 450 nm, and used at mask exposure Since the transmittance gradient with respect to i-line (365 nm), h-line (405 nm) and g-line (436 nm) is small, it is preferable because exposure can be performed without depending on the wavelength so much.

At this time, the semi-transmissive layer may be a layer containing chromium nitride as a main component.
If the semi-transmissive layer is a layer containing chromium nitride as a main component, the transmittance is substantially flat in the wavelength region of 300 to 700 nm, and thus the transmittance inclination to i-line, h-line, and g-line used at mask exposure Is preferable because it is possible to perform exposure independently of the wavelength.

At this time, it is preferable that the difference between the maximum value and the initial value of the transmittance of the semi-transmissive layer in a wavelength range of 300 nm to 700 nm is within 10%.
If the semi-transmissive layer is a layer containing chromium nitride as the main component, it is possible to keep the change in transmittance within 10% in the wavelength range of 300 to 700 nm, so mask exposure is performed independently of the wavelength. It is preferable because it is possible.

At this time, the optical density is preferably 3.5 or more.
The photomask substrate of the present invention has an optical density value of 3.5 or more, that is, 0.03% or less in terms of transmittance, and has a high light-shielding property, so that the irradiation light is appropriate during mask exposure It is possible to

At this time, it is preferable that the reflectance in a wavelength range of 350 nm to 600 nm is 20% or less.
The photomask substrate of the present invention has a reflectance of 25% or less in a wavelength range of 350 nm to 600 nm, and has a high antireflection effect, and prevents halation due to reflection of irradiation light during mask exposure. It is possible.

  According to the photomask of the present invention, the above object is to provide a transparent substrate, a semi-transmissive layer directly formed on the transparent substrate and having translucency for irradiated light, and the irradiated light formed on the semi-transmissive layer A light shielding layer for shielding light and a reflection preventing layer formed on the light shielding layer to prevent reflection of the irradiation light, the transparent portion comprising the transparent substrate, the transparent substrate, And a semi-transmissive portion formed of the transparent substrate and the semi-transmissive layer, wherein the semi-transmissive layer is mainly made of chromium nitride or chromium oxide. It is a layer which is a component, the light shielding layer is a layer which has titanium metal as a main component, and the antireflection layer is solved by a layer which has titanium oxynitride as a main component.

  According to the photomask of the present invention, since the difference in resistance between the semi-transmissive layer, and the light-shielding layer and the anti-reflective layer to the etching solution is used, the light-shielding layer and the anti-reflective layer are modified with the semi-transmissive layer etching liquid. In addition, the semitransparent layer is hardly modified or damaged by the etching solution of the light shielding layer and the antireflective layer, and the photomask having a high precision and a fine pattern is obtained. It becomes possible to offer.

At this time, it is preferable that the difference between the maximum value and the initial value of the transmittance of the semi-transmissive layer in a wavelength range of 350 nm to 450 nm is within 10%.
When the semi-transmissive layer is a layer mainly composed of chromium nitride or chromium oxide, the difference between the maximum value and the initial value of the transmittance is within 10% in the wavelength range of 350 nm to 450 nm, and used at mask exposure Since the transmittance gradient with respect to i-line (365 nm), h-line (405 nm) and g-line (436 nm) is small, it is preferable because exposure can be performed without depending on the wavelength so much.

At this time, the semi-transmissive layer may be a layer containing chromium nitride as a main component.
If the semi-transmissive layer is a layer containing chromium nitride as a main component, the transmittance is substantially flat in the wavelength region of 300 to 700 nm, and thus the transmittance inclination to i-line, h-line, and g-line used at mask exposure Is preferable because it is possible to perform exposure independently of the wavelength.

At this time, it is preferable that the difference between the maximum value and the initial value of the transmittance of the semi-transmissive layer in a wavelength range of 300 nm to 700 nm is within 10%.
If the semi-transmissive layer is a layer containing chromium nitride as the main component, it is possible to keep the change in transmittance within 10% in the wavelength range of 300 to 700 nm, so mask exposure is performed independently of the wavelength. It is preferable because it is possible.

At this time, the optical density of the light shielding portion is preferably 3.5 or more.
The photomask of the present invention has a high light shielding property, since the value of the optical density of the light shielding portion is 3.5 or more, that is, 0.03% or less in terms of transmittance, and light is irradiated during mask exposure. It is possible to block light appropriately.

At this time, it is preferable that the reflectance in a wavelength range of 350 nm to 600 nm of the light shielding portion is 20% or less.
The photomask of the present invention has a reflectance of 25% or less in the light shielding portion in a wavelength range of 350 nm to 600 nm, has a high anti-reflection effect, and generates halation due to reflection of irradiation light during mask exposure. It can be prevented.

  According to the method of manufacturing a photo mask of the present invention, the above object is achieved by a first resist coating step of coating a resist on the surface of the antireflective layer, and the mask having the first mask pattern formed thereon. A first exposure process for exposing the resist coated in the first resist coating process; a first resist removal process for removing an exposed portion of the resist after the first exposure process; and the resist Etching the antireflective layer and the light shielding layer exposed in the region from which the light source is removed with a first etching solution to form a light shielding pattern; and the resist remaining in the first resist removing step Through a first resist stripping step of stripping the second resist coating step of coating the resist again on the surface, and a mask on which a second mask pattern is formed. A second exposure step of exposing the resist coated in the second resist coating step; and a second resist removal step of removing an exposed portion of the resist after the second exposure step; The resist remaining in the second resist removing step is subjected to a second etching step of forming a semi-transmissive pattern by etching the semi-transmissive layer exposed in the region from which the resist is removed with a second etching solution. And performing a second resist peeling step of peeling.

According to the photomask manufacturing method of the present invention, the resist is exposed using the mask on which the first mask pattern is formed, the exposed portion of the resist is removed, and the light shielding layer and the first etching solution are used. The antireflective layer is etched, and then the resist is exposed with the mask on which the second mask pattern is formed, the exposed portion of the resist is removed, and the semitransparent layer is etched with the second etchant. A plurality of pattern formation areas can be formed on the surface of the transparent substrate.
That is, by utilizing the difference in resistance of the semi-transmissive layer, and the light shielding layer and the antireflective layer to the etching solution, the etching solution used for the etching of other layers is hardly subjected to modification or damage, and fine The pattern can be formed with high accuracy.

  At this time, it is preferable that the first etching solution is a mixed solution of potassium hydroxide, hydrogen peroxide and water, and the second etching solution is a mixed solution of cerium ammonium nitrate, perchloric acid and water. It is.

According to the photomask substrate of the present invention, the light shielding layer and the antireflective layer can be selectively etched by the first etching solution, and the semi-transmissive layer is selectively etched by the second etching solution. It is possible to manufacture a photomask with high precision and a fine pattern formed by wet etching, which has been difficult in the past, since the layer and the antireflective layer are hardly subject to modification or damage by the etching solution for each other Become.
Further, according to the photomask and the photomask manufacturing method of the present invention, the light shielding layer and the anti-reflection layer can be selectively etched by the first etching solution, and the semi-transmissive layer can be selectively etched by the second etching solution. The semitransparent layer, the light shielding layer and the antireflective layer are hardly modified or damaged by each other's etching solution, and therefore a photomask having high precision and a fine pattern by wet etching, which was conventionally difficult. It is possible to form
Therefore, according to the present invention, patterning can be performed by wet etching suitable for manufacturing of a large-sized photomask or mass production of a photomask, so that a short time and cost can be reduced as compared with patterning by conventional dry etching. It becomes possible to carry out the manufacture of a photomask.

It is a longitudinal cross-sectional view of the board | substrate for photomasks which concerns on one Embodiment of this invention. It is a longitudinal cross-sectional view of the photomask concerning one embodiment of the present invention. It is explanatory drawing which shows the process of patterning a photomask from the board | substrate for photomasks. It is explanatory drawing which shows the process of patterning a photomask. It is a longitudinal cross-sectional view of the board | substrate for photomasks which concerns on other embodiment of this invention. Is a graph showing the measurement results of the transmittance at each measurement point in the test example 1 of chromium nitride (CrN _x) thin film. A chromium nitride (CrN _x) thin film of Test Example 1 is a graph showing the measurement results of the titanium oxynitride of the Test Example _{2 (TiO z N 2-z} ) transmittance of the thin film. Chromium oxide in Test Example 3 is a graph showing the (CrO _y) measurements of the transmittance of the thin film. 5 is a graph showing the measurement results of reflectance at each measurement point of the photomask substrate of Example 1. FIG. It is a graph which shows the measurement result of the reflectance in 60 minutes after immersion before the substrate for photomasks of Example 1 in resist stripping solution, 90 minutes after immersion, 90 minutes after immersion, and 120 minutes after immersion. 7 is an electron micrograph of the cross section of the photomask substrate of Example 1 before the resist stripping liquid property test. 7 is an electron micrograph of a photomask substrate before patterning in Test Example 4; 7 is an electron micrograph of a photomask substrate on which a stripe pattern is formed in Test Example 4; It is a front photograph which image | photographed the edge part of the linear pattern in Experimental example 4 by enlarging, and is an electron micrograph which image | photographed the state after photoresist removal. It is a cross-sectional photograph which showed the cross-sectional shape of the linear pattern in Experiment 4, and is an electron micrograph which image | photographed the state after resist removal. It is a cross-sectional photograph which showed the cross-sectional shape of the linear pattern in Experiment 4, and is an electron micrograph taken in the state before resist removal. 15 is a graph showing the measurement results of reflectance at each measurement point of the photomask substrate of Example 2. FIG. It is a graph which shows the measurement result of the reflectance in 60 minutes after immersion, 90 minutes after immersion, and 90 minutes after immersion before immersing the board | substrate for photomasks of Example 2 in resist stripping solution. 7 is an electron micrograph of the cross section of the photomask substrate of Example 2 before the resist stripping liquid property test. Titanium Test Example 5 (Ti) / titanium oxynitride is a graph showing the _{(TiO z N 2-z)} measurement results of the sample and chromium (Cr) / chromium oxide (CrO _x) the reflectance of the sample.

  Hereinafter, a photomask substrate, a photomask, and a method of manufacturing the photomask according to an embodiment (the present embodiment) of the present invention will be described with reference to the drawings.

  1 is a longitudinal sectional view of a photomask substrate according to the present embodiment, FIG. 2 is a longitudinal sectional view of the photomask according to the present embodiment, and FIG. 3 is an illustration showing a process of patterning the photomask from the photomask substrate. FIG. 4 is an explanatory view showing a process of patterning a photomask. In FIGS. 1 to 4, in order to facilitate understanding of the invention, the film thickness of each layer is drawn thicker than the actual thickness, and the manufacturing process of the photomask substrate, photomask and photomask is schematically shown. It represents.

<Photomask substrate 2>
As shown in FIG. 1, the photomask substrate (also referred to as a photomask blank) 2 of the present embodiment is a transparent substrate 10, a semi-transmissive layer 20 formed on the surface of the transparent substrate 10, and a semi-transmissive layer A light shielding layer 33 formed on the surface of the light emitting diode 20 and an antireflective layer 35 formed on the surface of the light shielding layer 33 are formed. The photomask substrate 2 is a substrate from which the photomask 1 is manufactured. In the etching step and the photolithography step described later, the photomask substrate 2 is sequentially etched and patterned using different etching solutions. By doing this, it is possible to manufacture the photomask 1. The light shielding layer 33 and the antireflective layer 35 are collectively referred to as a composite layer 30.

<Photo mask 1>
As shown in FIG. 2, the photomask 1 of the present embodiment includes a transparent substrate 10, a semi-transmissive pattern 20 a formed on the surface of the transparent substrate 10, and a light-shielding layer pattern 33 a formed on the surface of the semi-transmissive pattern 20 a. And an antireflection layer pattern 35a formed on the surface of the light shielding layer pattern 33a. The semi-transmissive pattern 20a is a pattern formed by etching the semi-transmissive layer 20 of the photomask substrate 2. The light shielding layer pattern 33a is a pattern formed by etching the light shielding layer 33, and the antireflective layer pattern 35a is an antireflective layer. It is a pattern formed by etching 35. The light shielding pattern 30a of the present invention is formed by the light shielding layer pattern 33a and the antireflection layer pattern 35a.
In the photomask 1, the light shielding portion 1 a in which a part of the antireflective layer pattern 35 a (that is, the light shielding pattern 30 a) is exposed on the surface when viewed from the upper surface and the half A transmissive portion 1 b and a transparent portion 1 c in which a part of the transparent substrate 10 is exposed to the surface are formed.
Below, each member which comprises the board | substrate 2 for photomasks is demonstrated.

(Transparent substrate 10)
The transparent substrate 10 is a transparent substrate to be a base for forming a photomask pattern. In the present embodiment, the transparent substrate 10 is a sufficiently polished quartz substrate. As the transparent substrate 10, materials such as natural quartz glass, synthetic quartz glass, transparent resin film and the like can be used. The term "transparent" as used herein specifically means that the transmittance (Air Reference) in the wavelength range of 350 to 500 nm is included in the range of 80 to 95%.

(Semi-transmissive layer 20)
A semi-transmissive layer 20 is formed on the surface of the transparent substrate 10. The semi-transmissive layer 20 of the present embodiment is a layer having a phase shift function whose transmittance in a wavelength range of 350 to 500 nm is included in a range of 5 to 70%, and is chromium nitride (chromium nitride ( CrN _x : where 0 <x <1.5 or chromium oxide which is chromium oxide (CrO _y : where 0 <y <1.5) is used as the main component.
Having chromium nitride as the main component means that the total content of chromium nitride is 90% by mass or more when the entire semipermeable layer 20 is 100% by mass, and is 95% by mass or more Preferably, it is 99% by mass or more.
Having chromium oxide as the main component means that the total content of chromium oxide is 90% by mass or more when the entire semipermeable layer 20 is 100% by mass, and is 95% by mass or more Preferably, it is 99% by mass or more.
A film having such optical properties can be obtained by forming the dielectric material into a multilayer thin film based on the wave optical theory, but in consideration of the patterning property, the selectivity to the etching solution and the adhesion to the resist material It is not necessarily preferable from the viewpoint of tact time, pattern accuracy and the like. Therefore, it is preferable to form the semi-transmissive layer 20 as a single layer if possible without using a laminated structure. In addition, it is also necessary to ensure optical characteristics with a substance that is easy to pattern. Furthermore, from the viewpoint of photolithography, it is necessary to keep the reflectance as low as possible, and in this respect, a thin film having a suitable light absorption property is more convenient.

The semi-transmissive layer 20 and the light shielding layer 33 are characterized in that they exhibit resistance (insoluble or poorly soluble) to different etching solutions and exhibit solubility.
That is, the semitransparent layer 20 is insoluble or hardly soluble in the etching solution A (first etching solution) than the light shielding layer 33, and easily soluble in the etching solution B (second etching solution). is there. On the other hand, the light shielding layer 33 is more soluble in the etching solution A than the semi-transmissive layer 20 and insoluble or hardly soluble in the etching solution B. In the present embodiment, specifically, a mixed solution of potassium hydroxide, hydrogen peroxide and water is used as the etching solution A, and a mixed solution of cerium ammonium nitrate, perchloric acid and water is used as the etching solution B. There is.

  As described above, the semipermeable layer 20 and the light shielding layer 33 are different from each other in the insolubility or insolubility in the etching solution A and in the ease of solubility in the etching solution B. The light shielding layer 33 can be selectively etched by the etching solution A.

In this case, the semitransparent layer 20 is more insoluble or less soluble in the etching solution A than the light shielding layer 33, the solubility of the semitransparent layer 20 in the etching solution A is substantially zero, or light shielding It means extremely lower than the solubility of the layer 33.
Conversely, that the semitransparent layer 20 is more soluble in the etching solution B than the light shielding layer 33 means that the solubility of the semitransparent layer 20 in the etching solution B is extremely higher than that of the light shielding layer 33. Do.
Also, even when the light shielding layer 33 is insoluble or poorly soluble in the etching solution B than the semitransparent layer 20, the solubility of the light shielding layer 33 in the etching solution B is substantially zero or the semitransparent layer 20 It means that it is extremely lower than the solubility of
Conversely, that the light shielding layer 33 is more soluble in the etching solution A than the semitransparent layer 20 means that the solubility of the light shielding layer 33 in the etching solution A is extremely higher than that of the semitransparent layer 20. Do.

Specifically, in the present embodiment, the transmittance at 436 nm of the semi-transmissive layer 20 when immersed in the etching solution A at 30 ° C. for about 70 seconds (that is, the time when the light shielding layer 33 can be completely etched) is the etching solution. It is ± 0.5% or less of the transmittance before immersion in A. This indicates that the semi-transmissive layer 20 hardly changes (is not etched) by the etching solution A even under the condition that the light shielding layer 33 can be completely etched by the etching solution A.
In addition, the optical density of the light shielding layer 33 is −0.3 or less when immersed in the etching solution B at 30 ° C. for about 120 seconds (that is, the time during which the semitransparent layer 20 can be completely etched). This indicates that the light shielding layer 33 hardly changes (is not etched) by the etching solution B even under the condition that the semi-transmissive layer 20 can be completely etched by the etching solution B.
Thus, since the solubility to the etching liquid of the semi-transmissive layer 20 and the light shielding layer 33 differs, it becomes possible to selectively etch the semi-transmissive layer 20 and the light shielding layer 33 using the solubility characteristic.

From this investigation result, with respect to the chromium nitride (CrN _x ) film and the chromium oxide (CrO _y ) film having the etching resistance to the etching solution A and the optical characteristics, the selection of the etching solution and the possibility of the patterning property were examined. First, as a result of repeating studies on solubility and etching properties to various chemicals, the chromium nitride (CrN _x ) film and the chromium oxide (CrO _y ) film are different from hydrogen peroxide (H ₂ O ₂ ) in the photolithography process. It has been found that it is soluble in an alkali (eg, potassium hydroxide (KOH)) while being resistant to a mixture of potassium hydroxide (KOH) and water, and that a fine pattern is possible. . That is, the chromium nitride (CrN _x ) or chromium oxide (CrO _y ) film has resistance to the etching solution A for solubilizing the light shielding layer 33, in addition to the characteristic capable of obtaining desired optical characteristics. Also, it was found that the resist was resistant to the alkali contained in the resist removing solution. For this reason, in view of selectivity with respect to the light shielding layer 33, selecting a chromium nitride (CrN _x ) or chromium oxide (CrO _y ) film as the material of the semi-transmissive layer 20 itself has good etching characteristics. I understood it.

(Light shielding layer 33)
The light shielding layer 33 has a property of shielding almost 100% of the irradiation light, and is a layer formed on the surface of the semitransparent layer 20. In the present embodiment, metal titanium (Ti) is deposited to have a transmittance of 0.1% or less (optical density of 3.0 or more). As the material of the light shielding layer 33, metals such as molybdenum, aluminum, nickel and copper, oxides, nitrides and oxynitrides of these metals, and the like, as long as the main component is titanium And alloys of two or more types of metal compounds may be included.
Having titanium as the main component means that the total content of titanium is 90% by mass or more, based on 100% by mass of the entire light shielding layer 33, and is preferably 95% by mass or more, 99 It is more preferable that it is mass% or more.

  The light shielding layer 33 is more soluble in the etching solution A than the semitransparent layer 20 and has a property of being insoluble or hardly soluble in the etching solution B. For this reason, by using the etching solution A, it is possible to selectively etch only the light shielding layer 33 without etching the semi-transmissive layer 20.

(Antireflection layer 35)
The antireflection layer 35 is formed on the surface of the light shielding layer 33 and is a layer for reducing the reflectance. In this embodiment, titanium oxynitride is titanium oxynitride as a material of the antireflective layer _{35 (TiO z N 2-z} : wherein, 1 ≦ z <2) is used as a main component.
Having titanium oxynitride as the main component means that the total content of titanium oxynitride is 90 mass% or more, when the entire semipermeable layer 20 is 100 mass%, and is 95 mass% or more. It is more preferable that it is 99 mass% or more.

  When forming a fine pattern such as an LSI or the like using the photomask 1 obtained by patterning the photomask substrate 2, the reflection of the irradiation light is prevented by the anti-reflection layer 35 so that the interference of the reflection light is caused. It is possible to reduce moiré and halation.

  The antireflective layer 35 has the same etching characteristics as the light shielding layer 33. That is, the antireflective layer 35 has the property of being more soluble in the etching solution A than the semitransparent layer 20 and being insoluble or hardly soluble in the etching solution B. Therefore, by using the etching solution A, it is possible to etch only the antireflective layer 35 without etching the semi-transmissive layer 20. Further, since the antireflective layer 35 and the light shielding layer 33 are laminated, by using the etching solution A, the antireflective layer 35 and the light shielding layer 33 can be etched at once.

<Method of Manufacturing Photomask 1>
Next, a method of manufacturing the photomask 1 of the present embodiment will be described.
The photomask 1 of the present embodiment is wet-etched with respect to each layer using the photomask substrate 2 in which the semi-transmissive layer 20, the light shielding layer 33, and the antireflective layer 35 are sequentially laminated on the surface of the transparent substrate 10 by film formation. To form a predetermined pattern. As a film forming method, physical vapor deposition (PVD) using vacuum such as sputtering method, vapor deposition method, ion plating method or the like, or vapor phase deposition (CVD) such as plasma CVD or thermal CVD may be mentioned.

When forming a film by sputtering, reactive sputtering can also be used in addition to ordinary sputtering. One of the reactive sputtering apparatuses is an apparatus provided with a film forming area for sputtering a target, and a reaction area for performing plasma processing of a thin film after film formation by plasma of reactive gas. The second is an ordinary sputtering apparatus, which introduces a reactive gas during film formation and promotes reaction using plasma by sputtering.
Thereafter, film formation is performed by this reactive sputtering apparatus, chromium nitride (CrN _x ) as the semi-transmissive layer 20, metallic titanium (Ti) as the light shielding layer 33, titanium oxynitride (TiO _z N _2-z as the antireflective layer 35) Form a thin film).

(Deposition process)
First, the semi-transmissive layer 20 is formed. In forming the semi-transmissive layer 20, metallic chromium is used as a target. Before starting film formation, the transparent substrate 10 is set in the substrate holder of the sputtering apparatus. Chromium (Cr) ejected from the target by applying a voltage to the sputtering electrode by applying high voltage to the inside of the sputtering apparatus with a high vacuum to introduce inert gas (Ar) and reactive gas (N ₂ or O ₂ ) into the target Reacts with the reactive gas (N ₂ or O ₂ ) in the plasma to form a thin film of chromium nitride (CrN _x ) or chromium oxide (CrO _y ) on the surface of the transparent substrate 10. Thereby, the semi-transmissive layer 20 is formed on the surface of the transparent substrate 10 (semi-transmissive layer deposition step).

  Next, the light shielding layer 33 is formed. Before forming the light shielding layer 33, the target is exchanged from metal chromium to metal titanium (Ti). In this state, the interior of the sputtering apparatus is again brought into a high vacuum state, and the target is sputtered to form a light shielding layer 33 mainly composed of metallic titanium (Ti) on the surface of the semitransparent layer 20 Process).

  Subsequently, the antireflective layer 35 is formed. The anti-reflection layer 35 is made of titanium as the main component like the light-shielding layer 33, so that film formation can be performed subsequently to the film formation of the light-shielding layer 33 without replacing the target.

After forming the light shielding layer 33, an inert gas (Ar) and a reactive gas (O ₂ and N ₂ ) are introduced into the target, and a voltage is applied to the sputter electrode, whereby titanium (Ti) ejected from the target is removed. By reacting with reactive gases (O ₂ and N ₂ ) in plasma, a thin film of titanium oxynitride (TiO _z N _2-z ) is formed on the surface of the light shielding layer 33. Thereby, the anti-reflection layer 35 is formed on the surface of the light shielding layer 33 (anti-reflection layer film forming step).
Next, the photomask substrate 2 after film formation is cleaned by ultrasonic cleaning or the like to remove foreign substances on the surface.

(Patterning process)
A predetermined pattern is formed on the photomask substrate 2 having the laminated structure formed in this manner, using photolithography technology and etching technology. The pattern formation process (patterning process) will be described with reference to FIGS. 3 and 4.

  First, a photomask substrate 2 before patterning is prepared (FIG. 3A). The photomask substrate 2 can be manufactured using the above-described film formation technique such as sputtering. Next, a resist 50 is applied on the surface of the photomask substrate 2 using a method such as spin coating (FIG. 3B). The resist 50 is a photosensitive polymer material that is cured by ultraviolet light or the like. The resist coating method is not limited to spin coating, and for example, known methods such as spray coating and roll coating can be used. Next, the applied resist 50 is heated to a high temperature by a heater or the like, and prebaked (temporary curing). As described above, the resist 50 is coated on the surface of the photomask substrate 2 (first resist coating step).

  Next, a mask pattern is formed on the resist 50 using the mask original plate 60. The mask original plate 60 is a member on which a predetermined pattern (first mask pattern) is written in advance, and is a member for transferring the pattern to the resist 50. The resist 50 is exposed to ultraviolet light via the mask original plate 60 (FIG. 3C). Thereby, the surface of the resist 50 is exposed according to the first mask pattern (first exposure step).

  Subsequently, the resist 50 after exposure is immersed in a developer. Thus, the region of the resist 50 exposed to ultraviolet light is removed by the developer, and the anti-reflection layer 35 under the region is exposed on the surface (FIG. 3D). After partially removing the resist 50, the remaining resist 50 is heated to a high temperature and post-baked (main curing) using a heater or the like. Thereby, a part of the resist 50 is removed, and the same pattern as the first mask pattern is formed with the remaining resist 50 (first resist removal step).

  Next, the antireflective layer 35 and the light shielding layer 33 are etched using the etching solution A (that is, the first etching solution). The etching solution A is a mixed solution of potassium hydroxide, hydrogen peroxide and water. The etching solution A is filled in the bath, and the antireflective layer 35 exposed after removing the resist is completely immersed in the etching solution A. In this state, etching is performed while maintaining a predetermined etching temperature. The antireflective layer 35 and the light shielding layer 33 are both easily soluble in the etching solution A, and thus the etching solution A is collectively etched to form the same pattern as the remaining pattern of the resist 50.

  On the other hand, since the semi-transmissive layer 20 is insoluble or poorly soluble in the etching solution A, it has a role as an etching stop layer. For this reason, even if the light shielding layer 33 is etched by the etching solution A, the semi-transmissive layer 20 is not etched by the etching solution A and remains as it is (FIG. 3 (e)). As a result, the light shielding pattern 30a composed of the light shielding layer pattern 33a and the antireflection layer pattern 35a is formed on the surface of the semitransparent layer 20 (first etching step).

  Subsequently, the resist 50 remaining on the surface is dissolved with a release agent, and the surface is washed with pure water or the like (FIG. 3 (f)). Thereby, the same pattern as the first mask pattern is left on the surface of the transparent substrate 10 (first resist peeling step).

  Next, a resist 70 is applied to the surface and temporarily cured (FIG. 4 (b)). The resist 70 may use the same material as the resist 50 described above, or may use a different material such as curing performance. Thereby, the resist 70 is coated on the surface (second resist coating step).

  Subsequently, a mask pattern is formed on the resist 70 using the mask original plate 80. The mask original plate 80 is a member in which a predetermined pattern (second mask pattern) is written in advance similarly to the mask original plate 60. The resist 70 is exposed to ultraviolet light via the mask original plate 80 (FIG. 4C). Thereby, the surface of the resist 70 is exposed according to the second mask pattern (second exposure step).

  Next, the exposed resist 70 is immersed in a developing solution to remove a region of the resist 70 that is exposed to ultraviolet light (FIG. 4 (d)). Thereby, a part of the resist 70 is removed, and the same pattern as the second mask pattern is formed by the remaining resist 70 (second resist removal step).

  Subsequently, the semi-transmissive layer 20 is etched using the etching solution B (that is, the second etching solution). The etching solution B is a mixed solution of cerium ammonium nitrate, perchloric acid and water. The etchant B is filled in the bath, and the semipermeable layer 20 exposed after removing the resist is completely immersed in the etchant B. In this state, etching is performed while maintaining a predetermined etching temperature. Since the semi-transmissive layer 20 is easily soluble in the etching solution B, the semi-transmissive layer 20 is etched by the etching solution B and a pattern corresponding to the remaining pattern of the resist 70 is formed.

  On the other hand, since both the light shielding layer 33 and the anti-reflection layer 35 are insoluble or hardly soluble in the etching solution B, the light shielding pattern 30a formed from these layers is not etched by the etching solution B (FIG. 4 (e)) ). Thereby, the semi-transmissive pattern 20 a is formed on the surface of the transparent substrate 10 (second etching step).

  Finally, the resist 70 remaining on the surface is dissolved with a release agent, and the surface is washed with pure water or the like (FIG. 4F). Thereby, the same pattern as the second mask pattern remains on the surface of the transparent substrate 10 (second resist peeling step).

  When etching is performed by this method, as shown in FIG. 2, none of the semi-transmissive layer 20, the light shielding layer 33, and the anti-reflection layer 35 is etched in the portion not exposed by the first mask pattern. When the prevention layer 35 is not provided, a region (light shielding portion 1a) in which the light shielding layer 33 is exposed to the surface is formed. In a portion exposed with the first mask pattern and not exposed with the second mask pattern, there is a region (semi-transmissive portion 1b) where only the light shielding layer 33 and the anti-reflection layer 35 are etched and the semi-transmissive layer 20 is exposed on the surface It is formed. Furthermore, in the portion exposed with both the first mask pattern and the second mask pattern, the semi-transmissive layer 20, the light shielding layer 33, and the antireflective layer 35 are all etched to expose the transparent substrate 10 on the surface. (Transparent portion 1c) is formed.

  The photomask 1 manufactured in this manner can be used as a multi-tone mask or the like used when manufacturing a TFT panel or the like. In a manufacturing process of a TFT panel or the like, a transfer substrate is set to face the surface side (antireflection layer 35 side) of a multi-tone mask, and transfer light is irradiated from the transparent substrate 10 side to the transfer substrate. When light is irradiated from the side of the transparent substrate 10 toward the side of the antireflective layer 35, the light is blocked at the light shielding portion 1a, and light of an intermediate light amount (transmittance 5 to 70%) is transmitted at the semitransparent portion 1b. In the portion 1c, light is transmitted at a transmittance of approximately 100%. Therefore, on the opposite transfer substrate, transfer is performed at three different exposure levels: an unexposed portion by the light shielding portion 1 a, a semi-exposed portion by the semi-transmissive portion 1 b, and a completely exposed portion by the transparent portion 1 c.

  As described above, by using the photomask 1 of the present invention as a mask for pattern transfer in the photolithography technique, a plurality of transfer patterns having different exposure intensities can be easily formed. Moreover, the variation of exposure can be further increased by changing the wavelength and intensity of the light to be irradiated.

  The semi-transmissive layer 20 of the present embodiment is directly coated on the transparent substrate 10. Therefore, there is no need to form in advance a special layer for increasing the adhesion of the semi-transmissive layer 20 on the surface of the transparent substrate 10, and the film forming process can be shortened. In addition, the semi-transmissive layer 20 also has the function of reducing the reflectance from the glass surface side of the light shielding layer 33 at the time of exposure. As a result, it is possible to improve the pattern accuracy by reducing the halation to the irradiation light and reducing the moire phenomenon in the continuous fine stripe pattern portion and the like.

  On the other hand, as shown in FIG. 5, a metal compound layer 90 may be formed on the surface of the transparent substrate 10 to improve the adhesion to the semi-transmissive layer 20. In this case, the metal compound layer 90 preferably has a transmittance of 70% or more and less than 100%.

Such a metal compound layer 90 protects the surface of the transparent substrate 10 from the etching solution, and is formed of a material having high adhesion to the semi-transmissive layer 20. Examples of such materials include silicon oxide, aluminum oxide, and other metal oxides.
The metal compound layer 90 is formed on the surface of the transparent substrate 10 using a known film forming technique such as sputtering before forming the semitransparent layer 20.

  Hereinafter, although the manufacturing method of the photomask 1 using the board | substrate 2 for photomasks of this invention and the board | substrate 2 for photomasks is mentioned taking a specific example, and this invention is not limited to this. Absent.

<Test Example 1>
In Test Example 1, chromium nitride (CrN _x ) was used as the material of the semi-transmissive layer, and the optical characteristics were measured.

A glass substrate (6 inch square) was set in a sputtering apparatus, and reactive sputtering was performed using a metallic chromium target (purity 99.99% or more). In the sputtering process, chromium was nitrided by sputtering while introducing nitrogen gas to form a thin film (film thickness 56 Å) of chromium nitride (CrN _x : 0 <x <1.33).

Spectroscopic measurements were carried out at a total of nine points at four corner portions of the glass substrate laminated with chromium nitride, each central portion of four sides, and the central portion of the glass substrate.
Measurement sample: Glass substrate / CrN _x (film thickness 56 Å)
Spectrophotometer: U-4100 manufactured by Hitachi, Ltd.
Reference sample: Glass reference

  Moreover, the measurement of resistance value was performed using a resistivity meter (Mitsubishi Chemical Lorester GP).

The film thickness and the resistance value at each measurement point are shown in Table 1, and the transmittance is shown in FIG.
At each measurement point, the film thickness and the resistance value were almost equal, and it was found that chromium nitride can be formed uniformly.
In addition, the transmittance is almost flat (maximum value 57.94%, minimum value 52.08%) in the wavelength region of 300 to 700 nm, and i-line (365 nm), h-line (405 nm), g used in mask exposure Since no transmission slope for the line (436 nm) occurs, it is possible to perform exposure independent of wavelength.

Test Example 2
In Test Example 2, titanium oxynitride was used as the material of the semi-transmissive layer, and its optical properties were compared with the chromium nitride of Test Example 1.

A quartz substrate (6 inch square) was set in a sputtering apparatus, and reactive sputtering was performed using a metallic titanium target (purity 99.99% or more). In the sputtering step, titanium is oxidized by sputtering while introducing oxygen gas and nitrogen gas to form titanium oxynitride (TiO _z N _2-z : where 1 ≦ z <2) thin film (film thickness 360 Å) Formed.

Similar to Test Example 1, the transmittance was measured using a spectrophotometer (U-4100 manufactured by Hitachi, Ltd.). The transmittances of the chromium nitride (CrN _x ) of Test Example 1 and the titanium oxynitride (TiO _z N _2-z ) of Test Example 2 are shown in FIG. 7.
While chromium nitride has a substantially flat transmittance in a wavelength range of 300 to 700 nm, titanium oxynitride has a large change in transmittance according to the wavelength in a wavelength range of 300 to 600 nm. From these results, it was shown that it is preferable to use chromium nitride, which is a chromium-based material, as the material of the semipermeable layer, rather than using a titanium-based material.

<Test Example 3>
In Test Example 3, chromium oxide (CrO _y ) was used as the material of the semi-transmissive layer, and the optical characteristics were measured.

A quartz substrate (6 inch square) was set in a sputtering apparatus, and reactive sputtering was performed using a metallic chromium target (purity 99.99% or more). In the sputtering process, chromium was oxidized by sputtering while introducing oxygen gas to form a thin film (film thickness 270 Å) of chromium oxide (CrO _y : 0 <y <1.5).

Similar to Test Example 1, the transmittance was measured using a spectrophotometer (U-4100 manufactured by Hitachi, Ltd.). The transmittance is shown in FIG.
The chromium oxide film has a slope in transmittance in the 350 to 700 nm wavelength range, but the transmittance value in the i-line (365 nm), h-line (405 nm), and g-line (436 nm) wavelength range used during exposure Was within 30 to 40%.
Moreover, in the wavelength region of 350 to 450 nm, the maximum value of the transmittance was 38.37%, and the minimum value was 29.45%.
Therefore, it has been found that chromium oxide can also be used as the material of the semipermeable layer.

Example 1
In the present embodiment, each layer on the surface of the transparent substrate 10 is manufactured by a film forming method using vacuum. Specifically, a reactive sputtering apparatus using a reactive gas such as nitrogen gas or oxygen gas was used.

(Semi-transmissive layer deposition process)
In this example, first, a 800 mm × 920 mm glass substrate (transparent substrate 10) was set in a sputtering apparatus, and reactive sputtering was performed using a commercially available metallic chromium target (purity 99.99% or more). In the sputtering process, the semi-transmissive layer 20 is formed by nitriding chromium to form a thin film of chromium nitride (CrN _x : 0 <x <1.33) by sputtering while introducing nitrogen gas. did. The film thickness of the semitransparent layer 20 was 56 Å.
The target at this time is not limited to the one using a metal chromium target as in this example, but may be one obtained by bonding a sintered body of chromium nitride. In addition, since the degree of nitriding varies depending on the apparatus, it may be adjusted by appropriately combining the film forming conditions.

(Light shielding layer film formation process)
Next, the metal chromium target was changed to a metal titanium target (purity 99.99% or more), and the light shielding layer 33 was formed on the surface of the semitransparent layer 20 so as to have a film thickness of 1000 Å (100.0 nm). . At this time, a reactive gas was not introduced, and only metallic titanium (Ti) was deposited on the surface of the semipermeable layer 20. The light shielding layer 33 which functions as a light shielding layer is preferably sputtered at high speed under as high vacuum as possible in order to obtain an optical characteristic having an optical density (OD) of 3.0 or more. However, if the film thickness is rapidly increased by sputtering at high speed, the stress of the chromium film forming the light shielding layer 33 is increased. Therefore, it is preferable to perform high vacuum and high speed sputtering within an appropriate range.

(Antireflection layer film formation process)
Subsequently, the target was changed to another new metallic titanium target, and an antireflective layer 35 was formed to have a film thickness of 375 Å (37.5 nm). The sputtering process, by sputtering while introducing oxygen gas and nitrogen gas, titanium nitride and titanium _metal: converted (TiO z N _2-z where 1 ≦ y <2) on. The reflectance of titanium, which is a light shielding layer, is usually around 60%, and in order to reduce this reflectance, a film is formed with an appropriate refractive index and absorption according to the apparatus.
The general reflectance at this time is 25 to 30% at a wavelength of 650 nm and at least 6 to 8% at around 430 nm when the antireflective layer 35 is formed. By laminating the anti-reflection layer 35 in two or three layers, it is possible to suppress the reflectance to an average of several percent.

(Reflectance measurement)
Spectroscopic measurement was performed at a total of five points at four corner portions (Points 1 to 4) and the central portion (Point 5) in the photomask substrate of Example 1.
Measurement sample: Glass substrate / CrN _x (film thickness 56 Å) / Ti (1000 Å) / TiO _z N _2-z (374 Å)
Spectrophotometer: U-4100 manufactured by Hitachi, Ltd.
Reference sample: air reference

The film thickness and the optical density at each measurement point are shown in Table 2, and the reflectance is shown in FIG.
At each measurement point of the photomask substrate of Example 1, it was found that the film thickness and the optical density were almost equal, and the film was uniformly formed.
In addition, it was found that the optical density of the photomask substrate of Example 1 was 3.58 or more, and the light transmittance was sufficiently shielded to 0.03% or less.
Furthermore, the photomask substrate of Example 1 has a reflectance of 30% or less at a wavelength of 350 to 700 nm, 20% or less at 350 to 600 nm, 18% or less at 350 to 450 nm, and approximately 0.1% at around 430 nm. From this, it has been found that it has a high anti-reflection effect, and that it is possible to prevent halation due to reflection of irradiation light during mask exposure.

(Evaluation of resistance to resist stripping solution)
The resistance of the photomask substrate of Example 1 to a resist stripping solution was examined. A sulfuric acid / hydrogen peroxide solution (RS-30 manufactured by Lasa Kogyo Co., Ltd., sulfuric acid concentration 90 wt%, hydrogen peroxide 1 wt%) was used as a resist stripping solution. Before immersing the photomask substrate in a sulfuric acid / hydrogen peroxide solution, the reflectance was measured 60 minutes after immersion, 90 minutes after immersion, and 120 minutes after immersion. The results are shown in FIG.

  As shown in FIG. 10, it was found that the photomask substrate of Example 1 did not change in reflectance even after being immersed in the resist stripping solution for a long time, and had resistance to the resist stripping solution. .

  In addition, cross-sectional analysis of the photomask substrate was performed using a scanning electron microscope (SEM, JSM-6700F manufactured by JEOL Ltd.). As shown in FIG. 11, the ridge portion which suppresses the reflection of the end face is formed, and the etching surface is also observed as a clear boundary, and it was found that good etching can be performed.

<Test Example 4>
In Test Example 4, patterning was performed using the photomask substrate of Example 1.
The photomask substrate formed into a film in Example 1 was removed from the sputtering apparatus, and left in a storage for one week. Subsequently, the substrate for a photomask taken out of the storage is subjected to ultrasonic cleaning in each of a plurality of baths of alkaline detergent, neutral detergent, and pure water, and then a sample of 5 inches × 5 inches is cut out. A resist (AZP-1350 manufactured by AZ Electronic Materials Co., Ltd.) was coated on the entire surface of the photomask substrate to perform temporary curing (resist film thickness: about 700 nm). In the resist coating step, the surface of the photomask substrate is not treated with chemicals, plasma, ultraviolet light or the like.

  After temporary curing of the resist, exposure of stripe pattern (jet printer made by Oak Works: light source exposed with CHM-2000 super high pressure mercury lamp for 16 seconds), development (Tokyo Ohka Co., Ltd. PMER developer: temperature 30 ° C., 1 minute), Curing (Yamato DX402 dry oven: 120 ° C., 10 minutes) was performed. The stripe pattern used a line width of 10 μm. Subsequently, a first etching solution, a mixed solution of hydrogen peroxide, potassium hydroxide and water (hydrogen peroxide (35% aqueous solution): potassium hydroxide (30% aqueous solution): water = 16: 1: 32, reaction) A stripe pattern consisting of a light shielding pattern 30a in which a light shielding layer pattern 33a and an antireflection layer pattern 35a are laminated by simultaneously immersing the light shielding layer 33 and the antireflection layer 35 by immersing in a temperature of 30 ° C. and an etching time of 150 seconds. Formed. Next, the resist was removed with a predetermined chemical solution or the like.

FIG. 12 is an electron micrograph of the photomask substrate before patterning, and FIG. 13 is an electron micrograph of the photomask substrate on which a stripe pattern is formed.
As shown in FIG. 12, the titanium oxynitride surface on the surface of the photomask substrate before patterning was uniform.
As shown in FIG. 13, the stripe pattern was clearly formed on the photomask substrate after patterning.

  The overetch dimension of the light shielding pattern 30a in which the light shielding layer pattern 33a and the anti-reflection layer pattern 35a are combined at this time can not be measured with an optical microscope, so the photomask substrate 2 after pattern formation (after resist removal) Hereinafter, the “substrate” is simply cut in the longitudinal direction, and the cross section and the plane are observed with an electron microscope. The electron micrographs taken are shown in FIGS. FIG. 14 is an enlarged front view of an edge portion of a straight line pattern taken with an electron micrograph taken of the state after photoresist removal, and FIG. 15 is a cross-sectional picture showing the cross-sectional shape of the straight line pattern removed resist FIG. 16 is a cross-sectional photograph showing the cross-sectional shape of the straight line pattern taken after the state after the removal, and is an electron micrograph taken in the state before removing the resist.

Among these, it can be seen from the results of cross-sectional observation in FIG. 14 and FIG. 15 that the semi-transmissive layer 20 and the light shielding pattern 30 a are laminated on the surface of the transparent substrate 10. Further, it can be seen from the cross-sectional observation result of FIG. 16 that the light shielding pattern 30a is over-etched inward from the end of the resist. This over-etched dimension was found to be 0.22 μm from the photograph of FIG. In addition, as a result of front observation in FIG. 14, it was found that unevenness was generated at the edge portion of the straight line pattern, and the maximum and minimum widths thereof were 0.1 μm or less. At this time point, it was found that the chromium nitride (CrN _x ) film which is the semi-transmissive layer 20 was not particularly changed, and remained on the surface of the transparent substrate 10.

Example 2
In Example 2, a photomask substrate is manufactured in the same manner as in Example 1 except that a 6 inch × 6 inch (152.4 mm × 152.4 mm) quartz substrate (transparent substrate 10) is used, and Measurement and resistance evaluation to resist stripping solution were performed.

(Reflectance measurement)
Measurement sample: Quartz substrate / CrN _x (film thickness 56 Å) / Ti (1000 Å) / TiO _z N _2-z (334 Å)
Spectrophotometer: U-4100 manufactured by Hitachi, Ltd.
Reference sample: Quartz reference

The film thickness of the photomask substrate of Example 2 was 1390 Å, and the optical density was 3.59. The reflectance of the photomask substrate of Example 2 is shown in FIG.
It was found that the photomask substrate of Example 2 was sufficiently shielded from light as in the photomask substrate of Example 1, and had a high anti-reflection effect.

(Evaluation of resistance to resist stripping solution)
The result of having examined the resistance with respect to the resist stripping solution of the board | substrate for photomasks of Example 2 by the method similar to Example 1 is shown in FIG. As shown in FIG. 18, it was found that the photomask substrate of Example 2 was also resistant to the resist stripping solution.

  In addition, cross-sectional analysis of the photomask substrate was performed using a scanning electron microscope (SEM, JSM-6700F manufactured by JEOL Ltd.). As shown in FIG. 19, a ridge portion for suppressing reflection of the end face was formed, and the etching surface was observed as a clear boundary, and it was found that good etching can be performed.

<Test Example 5>
In Test Example 5, samples of titanium (Ti) / titanium oxynitride (TiO _z N _2-z ) and chromium (Cr) / chromium oxide (CrO _y ) were prepared as a combination of materials of the light shielding layer / antireflection layer. The optical characteristics (reflectance) were measured.

(Glass substrate / Ti / TiON)
The glass substrate was set in a sputtering apparatus, and a metal titanium target (purity 99.99% or more) was used to form a film on the glass substrate so as to have a film thickness of 700 Å (70.0 nm). At this time, a reactive gas was not introduced, and only metallic titanium (Ti) was deposited on the surface of the glass substrate.
Next, titanium titanium is converted to titanium oxynitride by sputtering using a metal titanium target (purity 99.99% or more) while introducing oxygen gas and nitrogen gas, and titanium oxynitride (TiO _z N) _2-z : Here, a thin film (film thickness 300 Å) of 1 ≦ y <2 was formed.

(Glass substrate / Cr / CrO)
The glass substrate was set in a sputtering apparatus, and a metal chromium target (purity 99.99% or more) was used to form a film on the glass substrate so as to have a film thickness of 700 Å (70.0 nm). At this time, no reactive gas was introduced, and only metal chromium (Cr) was formed on the surface of the glass substrate.
Next, metal chromium is converted into chromium oxide by sputtering using a metal chromium target (purity 99.99% or more) while introducing oxygen gas, and chromium oxide (CrO _y : 0 <y <1 A thin film (film thickness 300 Å) was formed.

  Similar to Test Example 3, the reflectance was measured from the film surface side using a spectrophotometer (U-4100 manufactured by Hitachi, Ltd.). The reflectances of the glass substrate / Ti / TiON (Bi-Ti) sample and the glass substrate / Cr / CrO (Bi-Cr) sample are shown in FIG.

  As shown in FIG. 20, the reflectance in the wavelength region of 400 nm to 550 nm or less was 20% or less in any of the samples. Therefore, it has good antireflection performance in the wavelength range of i-line (365 nm), h-line (405 nm) and g-line (436 nm), and has reflectivity in the wavelength range (400 nm to 550 nm) of low reflectance. It has been shown that it is possible to create photomasks with adjustable values at will.

DESCRIPTION OF REFERENCE NUMERALS 1 photomask 2 photomask substrate 1 a light shielding portion 1 b semi-transmissive portion 1 c transparent portion 10 transparent substrate 20 semi-transmissive layer (first layer)
20a semi-transmissive pattern 30 composite layer (second layer)
30a Light shielding pattern 33 Light shielding layer 33a Light shielding layer pattern 35 Antireflection layer 35a Antireflection layer pattern 50 Resist 60 Mask original plate 70 Resist 80 Mask original plate 90 metal compound layer

Claims (14)

A transparent substrate,
A semi-transmissive layer formed on the transparent substrate and semi-transmissive to irradiated light;
A light shielding layer formed on the semi-transparent layer to shield the irradiation light;
An antireflection layer formed on the light shielding layer to prevent reflection of the irradiation light;
A photomask substrate provided with
The semi-transmissive layer is a layer containing chromium nitride or chromium oxide as a main component,
The light shielding layer is a layer containing titanium metal as a main component,
The said anti-reflective layer is a layer which has a titanium oxynitride as a main component, The board | substrate for photomasks characterized by the above-mentioned.   The photomask substrate according to claim 1, wherein the difference between the maximum value and the initial value of the transmittance of the semi-transmissive layer in a wavelength range of 350 nm to 450 nm is within 10%.   The said semipermeable layer is a layer which has a chromium nitride as a main component, The board | substrate for photomasks of Claim 1 or 2 characterized by the above-mentioned.   The photomask substrate according to claim 3, wherein the difference between the maximum value and the initial value of the transmittance of the semi-transmissive layer in a wavelength range of 300 nm to 700 nm is within 10%.   5. The photomask substrate according to any one of claims 1 to 4, which has an optical density of 3.5 or more.   The photomask substrate according to any one of claims 1 to 5, wherein a reflectance in a wavelength range of 350 nm to 600 nm is 25% or less. A transparent substrate,
A semi-transmissive layer directly formed on the transparent substrate and having a semi-transmissive property to the irradiation light;
A light shielding layer formed on the semi-transparent layer to shield the irradiation light;
An antireflection layer formed on the light shielding layer to prevent reflection of the irradiation light;
A photomask with
A transparent portion made of the transparent substrate;
A light shielding portion comprising the transparent substrate, the semitransparent layer, the light shielding layer, and the antireflective layer;
And a semi-transmissive portion comprising the transparent substrate and the semi-transmissive layer,
The semi-transmissive layer is a layer containing chromium nitride or chromium oxide as a main component,
The light shielding layer is a layer containing titanium metal as a main component,
The photomask is characterized in that the antireflection layer is a layer mainly composed of titanium oxynitride.   8. The photomask according to claim 7, wherein the difference between the maximum value and the initial value of the transmittance of the semi-transmissive layer in a wavelength range of 350 nm to 450 nm is within 10%.   9. The photo mask according to claim 7, wherein the semi-transmissive layer is a layer containing chromium nitride as a main component.   The photomask according to claim 9, wherein the difference between the maximum value and the initial value of the transmittance of the semi-transmissive layer in a wavelength range of 300 nm to 700 nm is within 10%.   The optical density of the said light-shielding part is 3.5 or more, The photomask as described in any one of the Claims 7 thru | or 10 characterized by the above-mentioned.   The photomask according to any one of claims 7 to 11, wherein a reflectance of the light shielding portion in a wavelength range of 350 nm to 600 nm is 25% or less. A method of manufacturing a photomask using the photomask substrate according to any one of claims 1 to 6,
A first resist coating step of coating a resist on the surface of the antireflective layer;
A first exposure step of exposing the resist coated in the first resist coating step through a mask on which a first mask pattern is formed;
A first resist removing step of removing an exposed portion of the resist after the first exposure step;
A first etching step of forming a light shielding pattern by etching the antireflective layer and the light shielding layer exposed in the region from which the resist is removed with a first etching solution;
A first resist removing step of removing the resist remaining in the first resist removing step;
A second resist coating step of coating the resist on the surface again;
A second exposure step of exposing the resist coated in the second resist coating step through a mask on which a second mask pattern is formed;
A second resist removal step of removing an exposed portion of the resist after the second exposure step;
A second etching step of etching the semi-transmissive layer exposed in the region from which the resist is removed with a second etching solution to form a semi-transmissive pattern;
And D. a second resist removing step of removing the resist remaining in the second resist removing step. The first etching solution is a mixed solution of potassium hydroxide, hydrogen peroxide and water,
The method according to claim 13, wherein the second etching solution is a mixed solution of cerium ammonium nitrate, perchloric acid and water.

Images