Mask blank and photomask

Abstract

The invention relates to a mask blank and a photomask. This mask blank is provided with a transparent substrate, a light-shielding layer, an anti-reflection layer, and a water-resistant layer. The light shielding layer is disposed on the transparent substrate and contains nickel and titanium. The anti-reflection layer is disposed on the light shielding layer, and contains nickel, titanium, and oxygen. The water-resistant layer is disposed on the anti-reflection layer and contains nickel and titanium.

Description

Technical Field

[0001] The present invention relates to a mask blank and a photomask. Background Art

[0002] Photolithography is a well-known process used in the manufacture of FPDs (Flat Panel Displays) and semiconductor devices. A photomask blank (mask blank) is used to form the photomask used in the photolithography process. A mask blank has a structure in which a mask layer is laminated on one main surface of a transparent substrate such as a glass substrate.

[0003] In mask blank production, a mask layer, such as a light-shielding layer, with prescribed optical properties is formed on a transparent substrate. This mask layer can have a single layer or a stacked structure of multiple layers. A photomask is manufactured by forming a resist pattern on the mask layer and selectively etching away the mask layer using this resist pattern as a mask to form a prescribed mask pattern.

[0004] Mask blanks that include mask layers such as light-shielding and anti-reflection layers are required to exhibit excellent optical properties, such as light-shielding and optical reflection. Therefore, conventional mask blanks have used thin films composed of chromium metal, chromium oxide, chromium nitride, chromium oxynitride, and the like. In recent years, dual-layer film structures have also been used, leveraging the excellent optical properties of chromium metal or chromium compounds. This allows for the realization of mask blanks that also exhibit excellent low-reflection properties.

[0005] However, mask blanks containing Cr metal or Cr compounds generate waste containing Cr during etching processes such as patterning. This waste sometimes contains hexavalent Cr. Hexavalent Cr is a hazardous substance with a high environmental impact. Therefore, not only does strict attention need to be paid to the handling and storage of this waste, but waste disposal also incurs significant costs.

[0006] Therefore, many Cr-free mask blanks have been proposed. For example, Patent Document 1 describes a mask blank comprising an antireflection layer containing Ni, Mo, and Ti as main metal components, and a light-shielding layer containing Ni, Mo, and Ti as main metal components (Patent Document 1).

[0007] Patent Document 1: Japanese Patent Publication No. 2006-162942

[0008] However, in conventional mask blanks, where an anti-reflection layer and a light-shielding layer are laminated on the mask layer, the light reflectivity of the mask layer may fluctuate when pure water adheres to the mask layer surface. This means that the reflectivity of the mask layer changes before and after the so-called wet process. This situation can have a significant impact on the management of manufacturing conditions in the semiconductor manufacturing process.

[0009] To reduce the change in reflectivity caused by pure water adhering to the mask layer surface, a water-resistant layer can be stacked on the mask layer. However, stacking a water-resistant layer may affect the overall reflectivity and etching characteristics of the mask layer. Summary of the Invention

[0010] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a mask blank and a photomask having small fluctuations in reflectivity and excellent etching characteristics even when pure water adheres to the surface.

[0011] In order to solve the above-mentioned problems, the present invention adopts the following means.

[0012] One aspect of the present invention involves a mask blank comprising: a transparent substrate; a light-shielding layer, disposed on the transparent substrate, containing nickel (Ni) and titanium (Ti); an anti-reflection layer, disposed on the light-shielding layer, containing nickel (Ni), titanium (Ti) and oxygen (O); and a water-resistant layer, disposed on the anti-reflection layer, containing nickel (Ni) and titanium (Ti).

[0013] In the mask blank according to one aspect of the present invention, the thickness of the water-resistant layer may be 5.0 nm or greater.

[0014] In the mask blank according to one aspect of the present invention, when the total amount of nickel and titanium contained in the water-resistant layer is 100 atomic %, the nickel content may be in the range of 89.5 to 96.0 atomic % and the titanium content may be in the range of 4.0 to 10.5 atomic %.

[0015] In the mask blank according to one aspect of the present invention, the oxygen content may be in the range of 38.1 to 72.2 atomic % when the total amount of nickel, titanium, and oxygen contained in the antireflection layer is set to 100 atomic %.

[0016] In the mask blank according to one aspect of the present invention, the reflectivity with respect to light having a wavelength of 436 nm may be within a range of 5.0 to 25.0%.

[0017] A photomask according to one aspect of the present invention comprises: a transparent substrate; a light-shielding layer disposed on the transparent substrate and containing nickel (Ni) and titanium (Ti); an anti-reflection layer disposed on the light-shielding layer and containing nickel (Ni), titanium (Ti) and oxygen (O); and a water-resistant layer disposed on the anti-reflection layer and containing nickel (Ni) and titanium (Ti).

[0018] In the photomask according to one aspect of the present invention, the water-resistant layer may have a thickness of 5.0 nm or more.

[0019] In the photomask according to one aspect of the present invention, when the total amount of nickel and titanium contained in the water-resistant layer is 100 atomic %, the nickel content can be in the range of 89.5 to 96.0 atomic %, and the titanium content can be in the range of 4.0 to 10.5 atomic %.

[0020] In the photomask according to one aspect of the present invention, the content of oxygen may be in the range of 38.1 to 72.2 atomic % when the total amount of nickel, titanium, and oxygen contained in the antireflection layer is set to 100 atomic %.

[0021] In the photomask according to one aspect of the present invention, the reflectivity with respect to light having a wavelength of 436 nm may be within a range of 5.0 to 25.0%.

[0022] According to the present invention, a mask blank and a photomask having small fluctuation in reflectivity and excellent etching characteristics can be provided even when pure water adheres to the surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic cross-sectional view showing an example of a mask blank according to an embodiment of the present invention.

[0024] Figure 2 It is a schematic cross-sectional view showing an example of a photomask according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] Next, a mask blank and a photomask according to embodiments of the present invention will be described.

[0026] The photomask according to the embodiment is used, for example, in a photolithography process using exposure light having a wavelength of 436 nm. In addition, the mask blank according to the embodiment is used as a raw material when manufacturing the photomask.

[0027] In this embodiment, "low reflectivity fluctuation" means that the reflectivity of the mask blank or photomask of this embodiment, incident light with a wavelength of 436 nm, changes by 20% or less on the surface of the water-resistant layer before and after immersion in pure water for 48 hours. The change rate is expressed as a percentage (%) obtained by dividing the absolute value of the difference in reflectivity between the mask blank or photomask before and after application of pure water by the reflectivity before application of pure water.

[0028] In the present embodiment, “excellent etching characteristics” means that the dissolution time of a laminated film having a thickness of 100 to 110 nm formed of a light shielding layer, an antireflection layer, and a water-resistant layer in an etching solution is less than 600 seconds.

[0029] Figure 1An example of a mask blank according to this embodiment is shown. The mask blank according to this embodiment comprises a glass substrate (transparent substrate) 11, a light-shielding layer 12 formed on the glass substrate 11, an anti-reflection layer 13 disposed on the light-shielding layer 12, and a water-resistant layer 14 disposed on the anti-reflection layer 13. Furthermore, a photoresist layer may be formed on the water-resistant layer 14.

[0030] in addition, Figure 2 An example of a photomask according to this embodiment is shown. The photomask according to this embodiment is composed of a glass substrate 11 and a mask layer 15 formed on the glass substrate 11. The mask layer 15 is composed of Figure 1 The mask blank shown has a multilayer film structure in which a light shielding layer 12, an antireflection layer 13, and a water-resistant layer 14 are stacked. The mask layer 15 is formed by patterning into a predetermined shape.

[0031] As the glass substrate 11, a material having excellent transparency and optical isotropy is used. For example, a quartz glass substrate can be used. The size of the glass substrate 11 is not particularly limited and can be appropriately selected depending on the substrate to be exposed using the mask layer 15 (for example, a semiconductor, LCD (liquid crystal display), plasma display, organic EL (electroluminescence) display, or other FPD substrate).

[0032] In this embodiment, a rectangular substrate having a side of about 100 mm to a side of more than 250 mm can be used as the glass substrate 11. Further, a substrate having a thickness of less than 1 mm, a substrate having a thickness of several millimeters, or a substrate having a thickness of more than 10 mm can also be used as the glass substrate 11.

[0033] Furthermore, by polishing the surface of the glass substrate 11, the flatness of the glass substrate 11 can be reduced. For example, the flatness of the glass substrate 11 can be reduced to 5 μm or less. This allows the mask to have a deeper depth of focus, significantly contributing to the formation of fine, high-precision patterns. Furthermore, a relatively low flatness of 0.5 μm or less is considered good.

[0034] The light-shielding layer 12 has the following properties: that is, when exposure light with a wavelength of 436 nm is incident on the mask blank or photomask involved in this embodiment, the exposure light is not transmitted and the light is shielded. The light-shielding layer 12 contains nickel (Ni) and titanium (Ti). Preferably, the light-shielding layer 12 contains nickel and titanium, and contains a very small amount of impurities (inevitable impurities) as the remainder. The composition of the elements constituting the light-shielding layer 12 is not particularly limited. For example, when the total amount of nickel and titanium in the light-shielding layer 12 is set to 100 atomic %, the nickel content can be exemplified as being in the range of 80.0 to 98.0 atomic % and the titanium content can be exemplified as being in the range of 2.0 to 20.0 atomic %. In addition, the nickel content in the light-shielding layer 12 can be exemplified as being in the range of 85.5 to 96.5 atomic % and the titanium content can be exemplified as being in the range of 3.5 to 14.5 atomic %. By adjusting the nickel and titanium contents within this range, the optical density of the laminate composed of the water-resistant layer 14 , the antireflection layer 13 , and the light-shielding layer 12 to exposure light having a wavelength of 436 nm can be adjusted to a range of 7 or less.

[0035] The thickness of the light-shielding layer 12 is preferably in the range of 50 to 110 nm, more preferably in the range of 60 to 90 nm, and even more preferably in the range of 70 to 80 nm. By adjusting the thickness of the light-shielding layer 12 within the above range, the required reflectivity of the exposure light of the mask blank or mask can be maintained while shielding the exposure light.

[0036] The antireflection layer 13 has the property of suppressing reflection of exposure light having a wavelength of 436 nm when it enters the mask blank or photomask according to this embodiment. The antireflection layer 13 contains nickel (Ni), titanium (Ti), and oxygen (O). Preferably, the antireflection layer 13 contains nickel, titanium, and oxygen, with the remainder containing trace amounts of impurities (unavoidable impurities). The antireflection layer 13 contains oxygen. Therefore, the antireflection layer 13 contains one or more metal oxides of nickel and titanium.

[0037] When the total amount of nickel, titanium and oxygen is set to 100 atomic %, the oxygen content in the anti-reflection layer 13 is preferably in the range of 20 to 90 atomic %, can be in the range of 30.0 to 80.0 atomic %, can also be in the range of 38.1 to 72.2 atomic %, and can also be in the range of 40.0 to 70.0 atomic %.

[0038] By adjusting the oxygen content within this range, the reflectivity of the laminate composed of the water-resistant layer 14 , the antireflection layer 13 , and the light-shielding layer 12 to exposure light having a wavelength of 436 nm can be adjusted to a range of 5.0 to 25.0%.

[0039] The elemental composition of nickel and titanium in the antireflection layer 13 is not particularly limited. For example, the nickel content is in the range of 22.5 to 57.8 atomic % and the titanium content is in the range of 3.5 to 5.5 atomic %, assuming the total amount of nickel, titanium, and oxygen is 100 atomic %.

[0040] The thickness of the antireflection layer 13 is preferably in the range of 10 to 50 nm, more preferably in the range of 20 to 40 nm, and even more preferably in the range of 25 to 35 nm. By adjusting the thickness of the antireflection layer 13 within the above range, the required shielding rate of the exposure light for the mask blank or mask can be maintained while suppressing excessive reflection of the exposure light.

[0041] The water-resistant layer 14 has the function of suppressing changes in reflectivity when water adheres to the mask blank or photomask according to this embodiment. Pure water may adhere to a mask blank or photomask during photomask formation. If pure water adheres to a mask blank or photomask without the water-resistant layer 14, the reflectivity of the mask blank or photomask to exposure light may change before and after the water adheres. This change in reflectivity could potentially hinder semiconductor manufacturing processes or flat panel display manufacturing processes. Therefore, the mask blank or photomask according to this embodiment requires the water-resistant layer 14 to be disposed on the anti-reflection layer 13.

[0042] The water-resistant layer 14 involved in this embodiment contains nickel (Ni) and titanium (Ti). Preferably, the water-resistant layer 14 contains nickel and titanium, and contains a trace amount of impurities (inevitable impurities) as the remainder. In particular, if oxides are mixed into the water-resistant layer 14, the water resistance will be reduced, so it is necessary to avoid the mixing of oxides as much as possible. The composition of nickel and titanium in the water-resistant layer 14 is not particularly limited. For example, when the total amount of nickel and titanium in the water-resistant layer 14 is set to 100 atomic %, the nickel content can be exemplified as being in the range of 89.5 to 96.0 atomic % and the titanium content can be in the range of 4.0 to 10.5 atomic %. By adjusting the content of nickel and titanium within this range, the change rate of the reflectivity of the mask blank or photomask before and after the attachment of pure water can be adjusted to a range of 0 to 20%. Here, the change rate is the percentage (%) obtained by dividing the change in the reflectivity before and after the attachment of pure water by the reflectivity before the attachment of pure water.

[0043] In addition, the thickness of the water-resistant layer 14 needs to be 5.0 nm or more. The thickness of the water-resistant layer 14 is preferably in the range of 5.0 to 20.0 nm, and more preferably in the range of 5.0 to 10.0 nm. By adjusting the thickness of the water-resistant layer 14 within this range, the rate of change in the reflectivity of the mask blank or photomask before and after the attachment of pure water can be reduced. If the thickness of the water-resistant layer 14 is greater than 20.0 nm, when the light-shielding layer 12, the anti-reflection layer 13, and the water-resistant layer 14 of the mask blank are partially etched to manufacture the photomask, the time required to etch the water-resistant layer 14 becomes slower than the etching time of the light-shielding layer 12 and the anti-reflection layer. Furthermore, the end faces of the light-shielding layer 12, the anti-reflection layer 13, and the water-resistant layer 14 after etching become distorted. Therefore, the thickness of the water-resistant layer 14 is preferably not more than 20.0 nm. The thickness of the water-resistant layer 14 can be 7.0 nm or less. Furthermore, if the thickness of the water-resistant layer is less than 5.0 nm, the change in reflectivity before and after the application of pure water increases, which is not preferred. Since the water-resistant layer 14 is a thin metal film and tends to exhibit a metallic luster, its thickness affects the reflectivity of the mask blank or photomask. Therefore, it is best to precisely control the thickness of the water-resistant layer 14.

[0044] [Example]

[0045] Hereinafter, the present invention will be described in more detail with reference to examples.

[0046] like Figure 1 As shown, the light shielding layer 12 is formed on the transparent substrate 11 by using a sintered target containing nickel and titanium with a purity of 99.9% and performing DC sputtering in a vacuum chamber of a predetermined atmosphere.

[0047] Corning 1737 glass with a thickness of 0.7 mm was used as the transparent substrate 11. During the film formation process, the transparent substrate 11 was heated to 120°C using a quartz heater installed in a vacuum chamber. Ar was used as the atmospheric gas in the vacuum chamber. The atmospheric gas was introduced into the vacuum chamber through a gas inlet pipe installed near the target. The pressure during film formation was set to 6.7×10 -2 ~4.0×10 -1 Pa range. Under the constraints of the film forming device, the film thickness is controlled by input power, in order to obtain approximately The film thickness is about 1.75W (power density 2.6W / cm 2 ).

[0048] Next, a sintered target containing 99.9% pure nickel and titanium was used to perform DC sputtering in a vacuum chamber containing an oxygen atmosphere, thereby forming an antireflection layer 13 on the light shielding layer 12. During the film formation process, the transparent substrate 11 was heated to 120°C. Ar containing oxygen was used as the atmosphere gas in the vacuum chamber. The atmosphere gas was introduced into the vacuum chamber from a gas inlet pipe installed near the target. The pressure during film formation was set to 6.7×10 -2 ~4.0×10 -1 Pa range. Under the constraints of the film forming device, the film thickness is controlled by input power, in order to obtain approximately The film thickness is about 1.75W (power density 2.6W / cm 2 ).

[0049] Next, a water-resistant layer 14 was formed on the antireflection layer 13 by DC sputtering using a sintered target containing 99.9% pure nickel and titanium in a vacuum chamber with a predetermined atmosphere. During the film formation process, the transparent substrate 11 was heated to 120°C. Ar was used as the atmosphere gas in the vacuum chamber. The atmosphere gas was introduced into the vacuum chamber from a gas inlet pipe located near the target. The pressure during film formation was set to 6.7×10 -2 ~4.0×10 -1 Pa range. Under the constraints of the film forming device, the film thickness is controlled by input power, in order to obtain approximately The film thickness is about 1.75W (power density 2.6W / cm 2 ).

[0050] In this manner, the mask blanks shown in Table 1 were manufactured. The composition of each element in each layer in Table 1 was determined by Auger analysis (AES). Table 1 shows the range of the measured value of each element in the mask blank.

[0051] The etching performance of the resulting mask blanks, including the light-shielding layer, anti-reflection layer, and water-resistant layer, was evaluated. A nitric acid / hydrogen peroxide mixture was used as the solution for evaluating the etching performance. The composition of the nitric acid / hydrogen peroxide mixture was 69% nitric acid: pure water: 30% hydrogen peroxide = 1:2:2 (volume ratio). The nitric acid / hydrogen peroxide mixture was filled into a square flat bottom container, serving as a square shallow bottom container. To measure the etching time, the mask blank was immersed in the solution-filled square flat bottom container, and the time it took for the light-shielding layer, anti-reflection layer, and water-resistant layer to disappear was visually measured using a stopwatch. The results are shown in Table 2.

[0052] The resulting mask blank was subjected to light with a wavelength of 436 nm from the water-resistant layer side, and the reflectivity of the incident light was measured. Furthermore, the change in reflectivity before and after immersion in pure water for 48 hours was measured. The results are shown in Table 2.

[0053] As shown in Tables 1 and 2, Examples 1 and 2 have low reflectivity change rates and excellent etching performance.

[0054] On the other hand, the reflectance change rates of Comparative Examples 1 and 2 exceeded 20%, and the reflectance change rates were poor.

[0055]

[0056] [Table 2]

[0057]

[0058] Description of Reference Numerals

[0059] 11: Transparent substrate; 12: Light-shielding layer; 13: Anti-reflection layer; 14: Water-resistant layer; 15: Mask layer.

Claims

1. A mask blank comprising: Transparent substrate; a light shielding layer, disposed on the transparent substrate, containing nickel and titanium; an anti-reflection layer, disposed on the light-shielding layer, containing nickel, titanium, and oxygen; and The water-resistant layer is disposed on the anti-reflection layer and contains nickel and titanium.

2. The mask blank according to claim 1, wherein The thickness of the water-resistant layer is greater than 5.0 nm.

3. The mask blank according to claim 1, wherein When the total amount of nickel and titanium contained in the water-resistant layer is set to 100 atomic %, The nickel content is in the range of 89.5 to 96.0 atomic %, The titanium content is in the range of 4.0 to 10.5 atomic %.

4. The mask blank according to claim 1, wherein When the total amount of nickel, titanium, and oxygen contained in the antireflection layer is set to 100 atomic %, the content of oxygen is within a range of 38.1 to 72.2 atomic %.

5. The mask blank according to claim 1, wherein The reflectivity for light having a wavelength of 436 nm is within a range of 5.0 to 25.0%.

6. A photomask comprising: Transparent substrate; a light shielding layer, disposed on the transparent substrate, containing nickel and titanium; an anti-reflection layer, disposed on the light-shielding layer, containing nickel, titanium, and oxygen; and The water-resistant layer is disposed on the anti-reflection layer and contains nickel and titanium.

7. The photomask according to claim 6, wherein The thickness of the water-resistant layer is greater than 5.0 nm.

8. The photomask according to claim 6, wherein When the total amount of nickel and titanium contained in the water-resistant layer is set to 100 atomic %, The nickel content is in the range of 89.5 to 96.0 atomic %, The titanium content is in the range of 4.0 to 10.5 atomic %.

9. The photomask according to claim 6, wherein When the total amount of nickel, titanium, and oxygen contained in the antireflection layer is set to 100 atomic %, the content of oxygen is within a range of 38.1 to 72.2 atomic %.

10. The photomask according to claim 6, wherein The reflectivity for light having a wavelength of 436 nm is within a range of 5.0 to 25.0%.

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