Mask blanks and photomask

Abstract

To provide a mask blank and a photomask in which variation of reflectance is minimized even upon adhesion of pure water, while also exhibiting superior etching properties.SOLUTION: A mask blank is employed that comprises: a transparent substrate 11; a light-shielding layer 12 disposed on the transparent substrate 11 and containing Ni and Ti; an antireflection layer 13 disposed on the light-shielding layer 12 and containing Ni, Ti, and O; and a water-resistant layer 14 disposed on the antireflection layer 13 and containing Ni and Ti.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Photomask blanks (mask blanks) are used to form photomasks used in photolithography processes in the manufacture of FPDs (flat panel displays) and semiconductor devices, etc. Mask blanks consist of a mask layer laminated on one main surface of a transparent substrate such as a glass substrate.

[0003] In the manufacture of mask blanks, a film serving as a mask layer having predetermined optical properties, such as a light-shielding layer, is formed on a transparent substrate. This mask layer may be a single layer or a laminate of multiple layers. A resist pattern is formed on the mask layer, and the mask layer is selectively etched away using this resist pattern as a mask to form a predetermined mask pattern, thereby manufacturing a photomask.

[0004] Mask blanks equipped with mask layers such as a light-shielding layer and an anti-reflection layer are required to have excellent optical properties, such as light-shielding properties and optical reflectivity. For this reason, in conventional techniques, thin films made of Cr metal or Cr oxides such as Cr oxides and nitrides are used for mask blanks. In recent years, two-layer film configurations utilizing the excellent optical properties of Cr metal and its compounds have been used, which also make it possible to achieve excellent low reflectivity.

[0005] However, mask blanks made of Cr metal or its compounds generate waste containing Cr during the etching process of the pattern formation process, etc. If this waste contains hexavalent Cr, hexavalent Cr is harmful and has a high environmental impact, so not only does it require strict caution in handling and storing the waste, but it also incurs a great deal of cost for waste disposal.

[0006] For this reason, many mask blanks that do not contain Cr have been proposed. For example, Patent Document 1 describes a mask blank that includes an antireflection layer containing Ni, Mo, and Ti as the main metal components, and a light-shielding layer containing Ni, Mo, and Ti as the main metal components (Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-162942 Summary of the Invention [Problem to be solved by the invention]

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

[0009] To reduce the change in reflectance caused by the adhesion of pure water, it is possible to laminate a water-resistant layer on the mask layer. However, when a water-resistant layer is laminated, there are concerns about the effect on the reflectance and etching characteristics of the entire mask layer.

[0010] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a mask blank and a photomask that exhibit small fluctuations in reflectance even when pure water adheres to them, and that also have excellent etching characteristics. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention employs the following configuration. [1] A transparent substrate; a light-shielding layer containing Ni and Ti disposed on the transparent substrate; an antireflection layer disposed on the light-shielding layer and containing Ni, Ti, and O; a water-resistant layer containing Ni and Ti and disposed on the anti-reflection layer; A mask blank comprising: [2] The mask blank according to [1], wherein the water-resistant layer has a thickness of 5.0 nm or more. [3] The mask blank according to [1], wherein the water-resistant layer contains 89.5 to 96.0 atomic % of Ni and 4.0 to 10.5 atomic % of Ti, where the total amount of Ni and Ti contained in the water-resistant layer is taken as 100 atomic %. [4] The mask blank according to [1], wherein the O content is in the range of 38.1 to 72.2 atomic % when the total amount of Ni, Ti, and O in the antireflection layer is taken as 100 atomic %. [5] The mask blank according to [1], which has a reflectance to light with a wavelength of 436 nm in the range of 5.0 to 25.0%. [6] A transparent substrate; a light-shielding layer containing Ni and Ti disposed on the transparent substrate; an antireflection layer disposed on the light-shielding layer and containing Ni, Ti, and O; a water-resistant layer containing Ni and Ti and disposed on the anti-reflection layer; A photomask comprising: [7] The photomask according to [6], wherein the water-resistant layer has a thickness of 5.0 nm or more. [8] The photomask according to [6], wherein the water-resistant layer contains 89.5 to 96.0 atomic % of Ni and 4.0 to 10.5 atomic % of Ti, where the total amount of Ni and Ti contained in the water-resistant layer is taken as 100 atomic %. [9] The photomask according to [6], wherein the content of O in the antireflection layer is in the range of 38.1 to 72.2 atomic %, where the total amount of Ni, Ti, and O in the antireflection layer is taken as 100 atomic %.

[10] The photomask according to [6], which has a reflectance to light with a wavelength of 436 nm in the range of 5.0 to 25.0%. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a mask blank and a photomask that exhibit small fluctuations in reflectance even when pure water is attached and that also exhibit excellent etching characteristics. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a mask blank according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing an example of a photomask according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] A mask blank and a photomask according to an embodiment of the present invention will be described below. The photomask according to the embodiment is used in a photolithography process using exposure light with a wavelength of 436 nm, for example, and the mask blank according to the embodiment is used as a material for manufacturing the photomask.

[0015] In this embodiment, a small change in reflectance means that the rate of change in reflectance of incident light with a wavelength of 436 nm on the surface of the water-resistant layer before and after immersing the mask blank or photomask of this embodiment in pure water for 48 hours is 20% or less. The rate of change is a percentage (%) obtained by dividing the absolute value of the difference in reflectance before and after the application of pure water by the reflectance before the application of pure water.

[0016] In this embodiment, excellent etching characteristics means that the dissolution time of a 100 to 110 nm thick laminate film made up of a light-shielding layer, an anti-reflection layer and a water-resistant layer in an etchant solution is less than 600 seconds.

[0017] An example of a mask blank according to this embodiment is shown in Figure 1. The mask blank according to this embodiment is composed of 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. A photoresist layer may be formed on the water-resistant layer 14.

[0018] 2 shows an example of a photomask according to this embodiment. The photomask of this embodiment comprises a glass substrate (transparent substrate) 11 and a mask layer 15 formed on the glass substrate 11. The mask layer 15 is a multilayer film formed by laminating a light-shielding layer 12, an anti-reflection layer 13, and a water-resistant layer 14 of the mask blank shown in FIG. 1, which are patterned into a predetermined shape.

[0019] A material having excellent transparency and optical isotropy, such as a quartz glass substrate, is used as the glass substrate (transparent substrate) 11. The size of the glass substrate 11 is not particularly limited and is appropriately selected depending on the substrate to be exposed using the mask layer 15 (for example, a substrate for an FPD such as a semiconductor, LCD (liquid crystal display), plasma display, or organic EL (electroluminescence) display).

[0020] In this embodiment, a rectangular substrate with a side length of approximately 100 mm to 250 mm or more can be used as the glass substrate (transparent substrate) 11, and further, a substrate with a thickness of 1 mm or less, a substrate with a thickness of several mm, or a substrate with a thickness of 10 mm or more can also be used.

[0021] The surface of the glass substrate 11 may be polished to reduce the flatness of the glass substrate 11. The flatness of the glass substrate 11 can be, for example, 5 μm or less. This increases the depth of focus of the mask, which contributes greatly to the formation of fine and highly accurate patterns. Furthermore, the smaller the flatness, the better, as is 0.5 μm or less.

[0022] The light-shielding layer 12 has the ability to block exposure light having a wavelength of 436 nm when the exposure light is incident on the mask blank or photomask according to this embodiment by not transmitting the exposure light. The light-shielding layer 12 contains Ni and Ti. Preferably, the light-shielding layer 12 contains Ni and Ti, with the remainder being trace amounts of impurities. The composition of these elements is not particularly limited, but examples thereof include Ni: 80.0 to 98.0 atomic % and Ti: 2.0 to 20.0 atomic % when the total of Ni and Ti is 100 atomic %. Also, examples thereof include Ni: 85.5 to 96.5 atomic % and Ti: 3.5 to 14.5 atomic %. By adjusting the Ni and Ti contents within these ranges, the optical density of the laminate consisting of the water-resistant layer 14, the antireflection layer 13, and the light-shielding layer 12 with respect to exposure light having a wavelength of 436 nm can be adjusted to a range of 7 or less.

[0023] 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 as described above, it is possible to block the exposure light while maintaining the reflectance of the exposure light required for the mask blank or mask.

[0024] The antireflective layer 13 has the ability to suppress reflection of exposure light having a wavelength of 436 nm when the exposure light is incident on the mask blank or photomask according to this embodiment. The antireflective layer 13 contains Ni, Ti, and O (oxygen). Preferably, the antireflective layer 13 contains Ni, Ti, and O, with the remainder being a trace amount of impurities. Since the antireflective layer 13 contains oxygen, the antireflective layer 13 contains an oxide of at least one metal selected from Ni and Ti.

[0025] The oxygen content in the antireflection layer 13 is preferably 20 to 90 atomic %, or alternatively, 30.0 to 80.0 atomic %, 38.1 to 72.2 atomic %, or 40.0 to 70.0 atomic %, where the total of Ni, Ti, and O (oxygen) is 100 atomic %.

[0026] By adjusting the oxygen content within this range, the reflectance of the laminate consisting of the water-resistant layer 14, anti-reflection layer 13 and light-shielding layer 12 to exposure light with a wavelength of 436 nm can be adjusted to the range of 5.0 to 25.0%.

[0027] Furthermore, the composition of the Ni and Ti elements in the antireflection layer 13 is not particularly limited, but when the total of Ni, Ti, and O (oxygen) is taken as 100 atomic %, examples include Ni: 22.5 to 57.8 atomic % and Ti: 3.5 to 5.5 atomic %.

[0028] 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 as described above, it is possible to suppress excessive reflection of the exposure light while maintaining the necessary light blocking rate for the mask blank or mask.

[0029] The water-resistant layer 14 has the function of suppressing changes in reflectance 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 that does not have the water-resistant layer 14, the reflectance of the mask blank or photomask with respect to exposure light may change before and after the pure water adheres. If the reflectance changes, this may cause problems in semiconductor manufacturing processes or flat panel display manufacturing processes. Therefore, the mask blank or photomask according to this embodiment must have the water-resistant layer 14 disposed on the anti-reflection layer 13.

[0030] The water-resistant layer 14 according to this embodiment contains Ni and Ti. Preferably, the water-resistant layer 14 contains Ni and Ti, with the remainder being traces of impurities. In particular, the inclusion of oxides in the water-resistant layer 14 reduces water resistance, so it is necessary to avoid the inclusion of oxides as much as possible. The composition of Ni and Ti in the water-resistant layer 14 is not particularly limited, but examples include Ni: 89.5 to 96.0 atomic % and Ti: 4.0 to 10.5 atomic %, where the total of Ni and Ti is 100 atomic %. By adjusting the Ni and Ti contents within this range, the rate of change in reflectance of a mask blank or photomask before and after application of pure water can be adjusted to a range of 0 to 20%. Here, the rate of change is a percentage (%) obtained by dividing the amount of change in reflectance before and after application of pure water by the reflectance before application of pure water.

[0031] The thickness of the water-resistant layer 14 must be 5.0 nm or more, 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 maintaining the thickness of the water-resistant layer 14 within this range, the rate of change in reflectance of the mask blank or photomask before and after application of pure water can be reduced. If the thickness of the water-resistant layer 14 exceeds 20.0 nm, when partially etching the light-shielding layer 12, anti-reflection layer 13, and water-resistant layer 14 of the mask blank to produce a photomask, the time required to etch the water-resistant layer 14 will be longer than the time required to etch the light-shielding layer 12 and anti-reflection layer, resulting in distorted shapes of the edge surfaces of the light-shielding layer 12, anti-reflection layer 13, and water-resistant layer 14 after etching, which is undesirable. The thickness of the water-resistant layer 14 may be 7.0 nm or less. If the thickness of the water-resistant layer is less than 5.0 nm, the rate of change in reflectance before and after application of pure water will increase, which is undesirable. Since the water-resistant layer 14 is a thin metal film, it is likely to exhibit a metallic luster, and its thickness affects the reflectance of the mask blank or photomask, so it is advisable to precisely control the thickness of the water-resistant layer 14 . [Example]

[0032] The present invention will be described in more detail below with reference to examples. As shown in FIG. 1, a light-shielding layer 12 was formed on a transparent substrate 11 by DC sputtering in a vacuum chamber with a predetermined atmospheric gas using a sintered target containing Ni and Ti with a purity of 99.9%.

[0033] That is, the transparent substrate 11 was made of Corning 1737 glass having a thickness of 0.7 mm, and during film formation, the transparent substrate 11 was heated to 120°C by a quartz heater installed in the vacuum chamber. Ar was used as the atmospheric gas in the vacuum chamber, and was introduced from a gas inlet pipe installed near the target. The pressure during film formation was 6.7 × 10 -2 ~4.0×10 -1 Due to limitations of the film-forming device, the film thickness was controlled by input power, and approximately 1.75 W (power density 2.6 W / cm) was input to obtain a film thickness of approximately 1000 Å.

[0034] Next, an anti-reflection layer 13 was formed on the light-shielding layer 12 by DC sputtering in a vacuum chamber with an oxygen-containing atmosphere gas, using a sintered target containing Ni and Ti with a purity of 99.9%. During film formation, the transparent substrate 11 was heated to 120°C. Ar containing oxygen was used as the atmosphere gas in the vacuum chamber, and was introduced from a gas inlet pipe provided near the target. The pressure during film formation was 6.7 x 10 -2 ~4.0×10 -1 Due to limitations of the film-forming device, the film thickness was controlled by input power, and approximately 1.75 W (power density 2.6 W / cm) was input to obtain a film thickness of approximately 1000 Å.

[0035] Next, a water-resistant layer 14 was formed on the anti-reflection layer 13 by DC sputtering in a vacuum chamber with a predetermined atmospheric gas, using a sintered target containing Ni and Ti with a purity of 99.9%. During film formation, the transparent substrate 11 was heated to 120°C. Ar was used as the atmospheric gas in the vacuum chamber, and was introduced from a gas inlet pipe provided near the target. The pressure during film formation was 6.7 x 10 -2 ~4.0×10 -1Due to limitations of the film-forming device, the film thickness was controlled by input power, and approximately 1.75 W (power density 2.6 W / cm) was input to obtain a film thickness of approximately 1000 Å.

[0036] In this way, 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 also shows the range of measured values ​​for each element in the mask blanks.

[0037] The etching performance of the light-shielding layer, anti-reflection layer, and water-resistant layer of the obtained mask blanks was evaluated. The etching time was measured by filling a rectangular, shallow container called a tray with a nitric acid / hydrogen peroxide mixture (69% nitric acid: pure water: 30% hydrogen peroxide = 1:2:2 (volume ratio)), immersing the mask blanks in the solution, and visually measuring the time it took for the light-shielding layer, anti-reflection layer, and water-resistant layer to disappear with a stopwatch. The results are shown in Table 2.

[0038] The reflectance of the obtained mask blanks was measured by irradiating light with a wavelength of 436 nm from the water-resistant layer side. The reflectance change rate was also measured before and after immersing the mask blanks in pure water for 48 hours. The results are shown in Table 2.

[0039] As shown in Tables 1 and 2, Examples 1 and 2 had a low rate of change in reflectance and excellent etching performance. On the other hand, in Comparative Examples 1 and 2, the change rate of reflectance exceeded 20%, and the change rate of reflectance was inferior.

[0040] [Table 1]

[0041] [Table 2] [Explanation of symbols]

[0042] 11...transparent substrate, 12...light-shielding layer, 13...anti-reflection layer, 14...water-resistant layer, 15...mask layer.

Claims

1. A transparent substrate; a light-shielding layer disposed on the transparent substrate and containing Ni and Ti; an antireflection layer disposed on the light-shielding layer and containing Ni, Ti, and O; a water-resistant layer containing Ni and Ti and disposed on the anti-reflection layer; A mask blank comprising:

2. The mask blank according to claim 1 , wherein the water-resistant layer has a thickness of 5.0 nm or more.

3. 2. The mask blank according to claim 1, wherein, when the total amount of Ni and Ti contained in said water-resistant layer is taken as 100 atomic %, Ni is in the range of 89.5 to 96.0 atomic % and Ti is in the range of 4.0 to 10.5 atomic %.

4. 2. The mask blank according to claim 1, wherein the content of O is in the range of 38.1 to 72.2 atomic % when the total amount of Ni, Ti, and O in the antireflection layer is taken as 100 atomic %.

5. 2. The mask blank according to claim 1, wherein the reflectance to light with a wavelength of 436 nm is in the range of 5.0 to 25.0%.

6. A transparent substrate; a light-shielding layer disposed on a transparent substrate and containing Ni and Ti; an antireflection layer disposed on the light-shielding layer and containing Ni, Ti, and O; a water-resistant layer containing Ni and Ti and disposed on the anti-reflection layer; A photomask comprising:

7. The photomask according to claim 6 , wherein the water-resistant layer has a thickness of 5.0 nm or more.

8. 7. The photomask according to claim 6, wherein, when the total amount of Ni and Ti contained in said water-resistant layer is taken as 100 atomic %, Ni is in the range of 89.5 to 96.0 atomic % and Ti is in the range of 4.0 to 10.5 atomic %.

9. 7. The photomask according to claim 6, wherein the content of O in said antireflection layer is in the range of 38.1 to 72.2 atomic % when the total amount of Ni, Ti and O in said antireflection layer is taken as 100 atomic %.

10. 7. The photomask according to claim 6, wherein the reflectance to light with a wavelength of 436 nm is in the range of 5.0 to 25.0%.

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