Phase shift mask blanks, phase shift masks, and methods for manufacturing the same.

Abstract

This product provides phase-shift mask blanks that offer advantages in controlling the amount of phase shift, reducing etchant consumption, and optimizing throughput. [Solution] A phase shift mask blank comprising a substrate and a first layer formed on the substrate, wherein the first layer contains zirconium (Zr), silicon (Si), and nitrogen (N), and the transmittance per unit thickness of the first layer that gives a phase shift of 180° to light with a wavelength of 365 nm is 4% or more and 40% or less.

Description

Technical Field

[0001] The present invention relates to phase shift mask blanks, phase shift masks, and methods for manufacturing them. The present invention claims the priority of Japanese Patent Application No. 2022-067715 filed on April 15, 2022, and for designated countries where incorporation by reference is permitted, the contents described in that application are incorporated into the present application by reference.

Background Art

[0002] There is known a phase shift mask in which a phase shift layer made of chromium oxynitride is formed on a transparent substrate (Patent Document 1). Conventionally, improvement in the quality of phase shift masks has been desired.

[0003] Currently, a MoSi film with an i-line (365 nm) transmittance of 5% is used for silicide-based phase shift films. Also, for improving the phase shift effect, films with higher transmittance have been proposed, and a transmittance of up to about 10% can be achieved by increasing the nitrogen content. However, the problem with MoSi films is that the etching time by a wet process is long. The extension of the etching time causes the etching of the glass to progress, making it difficult to control the phase shift amount. Furthermore, it also leads to an increase in the consumption of the etchant and a decrease in throughput.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] According to the first embodiment, a phase shift mask blank is provided, comprising a substrate and a first layer formed on the substrate, wherein the first layer contains zirconium (Zr), silicon (Si), and nitrogen (N), and the transmittance per unit thickness of the first layer that gives a phase shift of 180° to light with a wavelength of 365 nm is 4% or more and 40% or less.

[0006] According to a second embodiment, a phase shift mask blank is provided, comprising a substrate and a first layer formed on the substrate, wherein the first layer is a laminate having four or more layers of nitride of a metal silicide containing zirconium (Zr) and silicon (Si), and the transmittance per unit thickness of the first layer that gives a phase shift of 180° to light with a wavelength of 365 nm is 4% or more and 40% or less.

[0007] According to a third embodiment, a phase shift mask blank is provided, comprising a substrate and a first layer formed on the substrate, wherein the first layer is a laminate having four or more layers of nitride of a metal silicide containing zirconium (Zr) and silicon (Si), and the inclination angle of the first layer is 55° or more and 90° or less.

[0008] According to the fourth aspect, a phase shift mask is provided in which a desired pattern is formed on a phase shift mask blank according to any of the first to third aspects.

[0009] A fifth aspect provides a method for manufacturing phase shift mask blanks, comprising a film deposition step of forming a first layer on a substrate, wherein the film deposition step involves forming a nitride layer of a metal silicide containing zirconium and silicon on the substrate four or more times to form the first layer.

[0010] A method for manufacturing a phase shift mask is provided, wherein the method for manufacturing a phase shift mask blank according to the fifth embodiment further comprises a pattern forming step for forming a desired pattern. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view showing an example of a phase-shift mask blank according to the embodiment. [Figure 2] This is a schematic cross-sectional view showing another example of a phase-shift mask blank according to the embodiment. [Figure 3] This is a schematic cross-sectional view of the phase shift mask according to the embodiment. [Figure 4] Figures (A) to (E) illustrate the method for manufacturing a phase shift mask according to the embodiment. [Figure 5] This is a schematic diagram of the exposure apparatus used in the exposure method of the embodiment. [Figure 6] This is a schematic diagram showing an example of a manufacturing apparatus for phase-shift mask blanks according to the embodiment. [Figure 7] This graph shows the transmittance of the ZrSi phase-shift mask blanks in the example at film thicknesses that produce a 180° phase shift when light with wavelengths of 300-600 nm is used. [Figure 8] This graph shows the transmittance of MoSi phase-shift mask blanks in a comparative example at film thicknesses that produce a 180° phase shift when light with wavelengths of 300-600 nm is used. [Figure 9] This graph shows the relationship between the sputter gas ratio (N2 / (Ar+N2)) and the etching rate for the ZrSi phase-shift mask blanks in the example and the MoSi phase-shift mask blanks in the comparative example. [Figure 10]This graph shows the relationship between the sputter gas introduction rate (Sputter gas ratio: N2 / (Ar+N2)) and the refractive index (Refractive index: n) of the ZrSi phase-shift mask blanks in the example and the MoSi phase-shift mask blanks in the comparative example. [Figure 11] This graph shows the relationship between the sputter gas introduction rate (Sputter gas ratio: N2 / (Ar+N2)) and the cross-section tilt angle for the ZrSi phase-shift mask blanks in the example and the MoSi phase-shift mask blanks in the comparative example. [Figure 12] This graph shows the relationship between the sputter gas ratio (N2 / (Ar+N2)) and the extinction coefficient (k) of the ZrSi phase-shift mask blanks in the example and the MoSi phase-shift mask blanks in the comparative example. [Figure 13] These are SEM images of the ZrSi phase-shift mask blanks in the example and the MoSi phase-shift mask blanks in the comparative example. [Figure 14] (A) SEM images of ZrSi phase-shift mask blanks consisting of 4 layers, (B) 6 layers, and (C) 8 layers, and sketches drawn based on the SEM images. [Modes for carrying out the invention]

[0012] The following describes embodiments of the present invention (hereinafter referred to as "these embodiments"). These embodiments are illustrative examples for explaining the present invention and are not intended to limit the present invention to the following content. The present invention can be implemented by modifying it as appropriate within the scope of its gist.

[0013] [Phase Shift Mask Blanks 100] The phase shift mask blank 100 of this embodiment, shown in Figure 1, will be described. The phase shift mask blank 100 comprises a substrate 10 and a phase shift layer 20 formed on the surface (substrate surface) 10a of the substrate 10. A phase shift mask 300 (see Figure 3) can be manufactured from the phase shift mask blank 100 by forming a predetermined pattern 50 on the phase shift layer 20. The phase shift mask 300 is used when manufacturing display devices such as FPDs (Flat Panel Displays) and semiconductor devices such as LSIs (Large Scale Integrations).

[0014] For example, synthetic quartz glass can be used as the material for the substrate 10. However, the material of the substrate 10 is not limited to synthetic quartz glass. The substrate 10 just needs to transmit the exposure light of the exposure apparatus in which the phase shift mask 300 is used sufficiently.

[0015] The phase shift layer 20 contains zirconium (Zr), silicon (Si), and nitrogen (N). As shown in FIG. 3, in the phase shift mask 300, a part of the phase shift layer 20 is removed from the substrate surface 10a by wet etching, and the removed portion forms a predetermined pattern 50 on the surface of the phase shift layer 20. The pattern 50 (removed portion, recess) is defined by the side surface 21 of the phase shift layer 20 exposed by wet etching and the exposed substrate surface 10a. FIG. 3 shows a cross section orthogonal to the substrate surface 10a of the phase shift layer 20. In the cross section shown in FIG. 3, it can be determined that the accuracy of the pattern 50 formed on the phase shift mask 300 is higher as the inclination angle θ of the side surface 21 of the phase shift layer 20 that defines the pattern 50 from the substrate surface 10a is closer to 90°. The inclination angle θ is an angle including the phase shift layer 20 among the angles formed by the side surface 21 that defines the pattern 50 (recess) of the phase shift layer 20 and the substrate surface 10a in a cross section orthogonal to the substrate surface 10a of the phase shift layer 20. Therefore, the inclination angle θ is preferably closer to 90°. Specifically, the inclination angle θ is preferably 45° to 90°, more preferably 60° as the lower limit value, and even more preferably 70°. The upper limit value may be 85° or 75°. FIG. 3 shows a state where θ = 90°. The inventors of the present invention have found that by forming the phase shift layer 20 with a plurality of layers, in the phase shift mask 300 manufactured from the phase shift mask blanks 100, the inclination angle θ increases (approaches 90°), and the pattern accuracy of the phase shift mask 300 is improved. Therefore, the phase shift layer 20 of the present embodiment preferably consists of a plurality of layers, and for example, it can be a laminate of 4 to 10 layers. The lower limit is 5 layers, more preferably 6 layers. By laminating the phase shift layer 20 in this way, the inclination angle θ can be increased, and thus the pattern accuracy can be improved by reducing the side etching amount. Although the phase shift layer 20 in FIGS. 1 to 5 is depicted as a single layer (one layer), it is depicted in a state where a plurality of layers are laminated.

[0016] The phase shift layer 20 may not contain elements other than Zr, Si, and N, or may contain them as a small amount of impurities that do not affect the effect.

[0017] In addition, the refractive index of the phase shift layer 20 of the phase shift mask blank of the present embodiment has a high value. By increasing the refractive index, the thickness of the phase shift layer 20, which is derived from the following formula: d = λ / (2(n - 1)) (d: thickness of the phase shift layer 20, λ: wavelength of exposure light, n: refractive index of the phase shift layer 20 at wavelength λ), can be reduced. By reducing the thickness required for film formation, the film can be formed more uniformly on the substrate 10. Also, if the thickness of the phase shift layer 20 can be reduced, the amount of side etching described later can be reduced, and a pattern 50 closer to the designed dimensions can be formed (the pattern accuracy is improved).

[0018] The refractive index of the phase shift layer 20 of the present embodiment with respect to light with a wavelength of 365 nm may be, for example, 2.70 to 2.90. A more preferable lower limit value of the refractive index is 2.75, and more preferably 2.80. By setting such a high refractive index, it becomes possible to reduce the film thickness when the phase shift amount is 180°.

[0019] The attenuation coefficient of the phase shift layer 20 of the present embodiment with respect to light with a wavelength of 365 nm may be, for example, 0.13 to 0.80. Also, a more preferable upper limit value of the attenuation coefficient is 0.70, more preferably 0.60, and even more preferably 0.50.

[0020] The phase shift layer 20 functions as a phase shifter that locally changes the phase of the exposure light irradiated in the exposure process using the phase shift mask 300. Therefore, the phase shift layer 20 needs to transmit the exposure light to a certain extent. The transmittance of the phase shift layer 20 with respect to the exposure light (for example, light with a wavelength of 330 nm to 470 nm) is preferably 3% or more and 85% or less. Representative exposure lights used in the exposure process using the phase shift mask 300 include, for example, deep ultraviolet rays (DUV, wavelengths: 302 nm, 313 nm, 334 nm), i-line (wavelength: 365 nm), h-line (wavelength: 405 nm), and g-line (wavelength: 436 nm). These can be used as monochromatic light or as composite light.

[0021] Here, the transmittance of light at a wavelength of 365 nm in a film thickness that gives a phase shift of 180° with light at a wavelength of 365 nm may be 4% or more and 40% or less, with a lower limit of 5% and a more preferable 8%. The upper limit is preferably 38% and a more preferable 37%. Furthermore, the transmittance of light at a wavelength of 405 nm in a film thickness that gives a phase shift of 180° with light at a wavelength of 405 nm may be 5% to 50%, with a lower limit of 7% and a more preferable 8%. Furthermore, the upper limit is preferably 49% and a more preferable 48%. Furthermore, the transmittance of light at a wavelength of 436 nm in a film thickness that gives a phase shift of 180° with light at a wavelength of 436 nm may be 8% to 65%, with a lower limit of 9% and a more preferable 10%. Furthermore, the upper limit is preferably 63% and a more preferable 60%.

[0022] The phase shift layer 20 preferably changes (shifts) the phase of the exposure light irradiated in the exposure process using the phase shift mask 300 by approximately 180° (phase shift amount: approximately 180°). That is, the phase shift layer 20 preferably changes the phase of the exposure light transmitted through it (for example, light with a wavelength of 330 nm to 470 nm) by 160° to 200° (180° ± 20°), 170° to 190° (180° ± 10°), or 175° to 185° (180° ± 5°).

[0023] The amount of phase shift can be adjusted by changing the refractive index, thickness (film thickness), etc. of the phase shift layer 20 to match the wavelength of the light (exposure light) transmitted through the phase shift mask 300. The thickness of the phase shift layer 20 can be designed to achieve a phase shift of approximately 180°, taking into account the characteristics of the phase shift layer 20, such as the refractive index, and the wavelength of the transmitted light (exposure light). That is, the thickness d of the phase shift layer 20 can be designed based on the formula: d = λ / (2(n-1)) (d: thickness of the phase shift layer 20, λ: wavelength of the exposure light, n: refractive index of the phase shift layer 20 at wavelength λ). The thickness of the phase shift layer 20 is preferably, for example, 90 nm to 125 nm, more preferably a lower limit of 94 nm, and even more preferably 96 nm. The upper limit of a more preferable thickness of the phase shift layer 20 is 116 nm, and even more preferably 110 nm. By using such film thicknesses, the etching time required to achieve a 180° phase shift is shortened, and damage to the glass is reduced.

[0024] The phase shift mask blank 100 is manufactured using a method described later. For example, the phase shift mask blank 100 may be manufactured by depositing a phase shift layer 20 on a substrate 10 using reactive sputtering, which will be described in the examples below.

[0025] [Phase Shift Mask Blanks 200] The phase-shift mask blank 200 shown in Figure 2 will now be described. The phase-shift mask blank 200 comprises a substrate 10, a phase-shift layer 20 formed on the substrate surface 10a, and an etching mask layer (chromium compound layer) 30 containing a chromium compound formed on the phase-shift layer 20. The configuration of the phase-shift mask blank 200 is the same as that of the phase-shift mask blank 100 shown in Figure 1, except for the presence of the etching mask layer 30. The phase-shift mask blank 200 shown in Figure 2 provides the same effects as the phase-shift mask blank 100, and further, by having the etching mask layer 30, it provides the effects described below.

[0026] Similar to the phase-shift mask blanks 100, a phase-shift mask 300 (see Figure 3) can be manufactured from the phase-shift mask blanks 200 by forming a predetermined pattern 50 on the phase-shift layer 20. When the predetermined pattern 50 is formed on the phase-shift layer 20 by wet etching, a photoresist layer 40 is formed on the phase-shift mask blanks 200 (see Figure 4(A)). Here, the phase-shift layer (ZrSiN-based layer) 20 has low adhesion to the photoresist layer 40. Therefore, if the photoresist layer 40 is formed directly on the phase-shift layer 20, there is a risk that the photoresist layer 40 will peel off during wet etching. To address this, the phase-shift mask blanks 200 are provided with an etching mask layer 30 that has adhesion to both the photoresist layer 40 and the phase-shift layer 20, thereby suppressing the peeling of the photoresist layer 40 during wet etching.

[0027] The material of the etching mask layer 30 is not particularly limited and can be any material that enhances the adhesion between the photoresist layer 40 and the phase shift layer 20. For example, chromium compounds such as chromium nitride and chromium oxide may be used. In the manufacturing of the phase shift mask 300, the photoresist layer 40 is exposed to light with a wavelength of 350 nm to 450 nm. Therefore, it is preferable that the etching mask layer 30 provided beneath the photoresist layer 40 has a low reflectivity to light with a wavelength of 350 nm to 450 nm, and also functions as an anti-reflective layer, with chromium oxide being more preferable as the anti-reflective layer. By suppressing the reflection of exposure light, multiple reflections of exposure light within the photoresist layer 40 are suppressed, improving the pattern accuracy of the phase shift mask 300. For example, the reflectivity of the etching mask layer 30 to light with a wavelength of 413 nm is preferably 15% or less. The etching mask layer 30 may be a single layer or formed from multiple layers. When the etching mask layer 30 is formed from multiple layers, it is preferable that the reflectivity to exposure light of the layer directly beneath the photoresist layer 40 is low. For example, the etching mask layer 30 may consist of a chromium nitride layer 31 formed on the phase shift layer 20 and a chromium oxide layer 32 formed on the chromium nitride layer 31. The chromium oxide layer 32 can, for example, suppress the reflectance of light with a wavelength of 413 nm to about 11%.

[0028] The thickness of the etching mask layer 30 is not particularly limited and can be adjusted as appropriate, for example, it may be 10 nm to 120 nm. When the etching mask layer 30 is composed of a chromium nitride layer 31 and a chromium oxide layer 32, for example, the thickness of the etching mask layer 30 is preferably 80 to 120 nm, and the ratio of the thickness of the chromium nitride layer 31 to the thickness of the chromium oxide layer 32 is preferably 6:4 (3:2) to 8:2 (4:1). If the etching mask layer 30 is too thin, the etching time will be shortened, making it difficult to control the CD (Critical dimension) within the phase shift layer plane (i.e., control the line width of the pattern 50). Also, if the etching mask layer 30 is too thick, the amount of side etching will be large, making it difficult to obtain the pattern dimensions as designed. When wet etching the phase shift layer 20 based on the etching mask layer 30 (see Figure 4(D)), the phase shift layer 20 is etched isotropically by the etching solution. Therefore, in addition to etching the phase shift layer 20 in a direction perpendicular to the substrate 10, the phase shift layer 20 is also etched in a lateral direction perpendicular to the vertical direction. This phenomenon of etching progressing in the lateral direction is called side etching. For this reason, if the etching mask layer 30 is too thick, or if the phase shift layer 20 is too thick as described above, there is a risk that etching will occur with a width wider than the desired pattern width.

[0029] The manufacturing method for the phase shift mask blank 200 is not particularly limited, and general-purpose methods can be used. For example, the phase shift mask blank 200 may be manufactured by depositing a phase shift layer 20 and an etching mask layer 30 on a substrate 10 using reactive sputtering, which will be described later in Figure 6 and in the examples.

[0030] Figure 6 is a schematic diagram showing a manufacturing apparatus 600 for phase-shift mask blanks 100 and 200 according to this embodiment, and is a view of the inside of the manufacturing apparatus 600 from above. The film deposition apparatus 600 shown in Figure 6 is an in-line sputtering apparatus and comprises a loading chamber 601 for loading substrates 10 for manufacturing phase-shift mask blanks 100 and 200, a first sputtering chamber 602, a buffer chamber 603, a second sputtering chamber 604, and an unloading chamber 605 for unloading the manufactured phase-shift layer 20.

[0031] The substrate tray P is a frame-shaped tray on which a substrate 10 for forming the phase shift layer 20 can be placed, and the outer edge portion of the substrate 10 is supported and placed on it. The substrate 10 is placed on the substrate tray P such that the surface on which the phase shift layer 20 (ZrSiN-based layer), the light-shielding film that will become the etching mask layer 30 (chromium compound layer), and the anti-reflective film will be formed is facing downwards. In the film deposition apparatus 600, as will be described later, while maintaining the state in which the surface of the substrate 10 is facing the target, the substrate tray P on which the substrate 10 is placed is transported to the position of the buffer chamber 603 in the direction indicated by the solid arrow Q in Figure 6, thereby forming the first phase shift layer 20 (ZrSiN-based layer) on the surface of the substrate 10, and a phase shift mask blank 100 having a single layer of phase shift layer 20 is manufactured.

[0032] As shown by the solid arrow Q, after the first phase shift layer 20 is formed, the substrate tray P is repeatedly transported between the loading chamber 601 and the buffer chamber 603, thereby manufacturing a phase shift mask blank 100 having a phase shift layer 20 consisting of a number of layers equal to the number of transports. Note that the same ZrSiN-based layers can be formed whether the substrate tray P is transported from the loading chamber 601 to the buffer chamber 603 or from the buffer chamber 603 to the loading chamber 601.

[0033] After the phase shift mask blanks 100 are manufactured, the substrate tray P is further transported from the buffer chamber 603 to the discharge chamber 605, as indicated by the dotted arrow R, thereby forming an etching mask layer 30 (chromium compound layer) on the phase shift layer 20, and manufacturing a phase shift mask blank 200.

[0034] The input chamber 601, the first sputtering chamber 602, the buffer chamber 603, the second sputtering chamber 604, and the output chamber 605 are each separated by shutters (not shown). The input chamber 601, the first sputtering chamber 602, the buffer chamber 603, the second sputtering chamber 604, and the output chamber 605 are each connected to an exhaust system (not shown), and the inside of each chamber is exhausted.

[0035] A first target 606 (ZrSi) is provided inside the first sputtering chamber 602, and a second target 607 (Cr) is provided inside the second sputtering chamber 604. The first sputtering chamber 602 and the second sputtering chamber 604 are each provided with a DC power supply (not shown) that supplies power to the first target 606 (ZrSi) and the second target 607 (Cr), respectively.

[0036] The first sputtering chamber 602 is provided with a first gas inlet 608 for introducing sputtering gas into the first sputtering chamber 602. The first target 606 is a sputtering target for forming a ZrSiN-based layer and is made of a material containing zirconium (Zr) and silicon (Si). Specifically, the first target 606 is made of a material selected from zirconium, zirconium oxide, zirconium nitride, zirconium carbide, silicon, silicon oxide, silicon nitride, silicon carbide, etc. For example, in order to form a ZrSiN film, a mixed gas of nitrogen-containing gas and an inert gas (such as argon gas) is introduced through the first gas inlet 608.

[0037] The second sputtering chamber 604 is provided with a second gas inlet 609 for introducing sputtering gas into the second sputtering chamber 604. The second target 607 is a sputtering target for forming a chromium compound layer and is made of a chromium-containing material. Specifically, the second target 607 is made of a material selected from chromium, chromium oxides, chromium nitrides, chromium carbides, etc. For example, in order to form a CrCN film as a light-shielding film, a mixed gas of a nitrogen or oxygen-containing gas and an inert gas (such as argon gas) is introduced through the second gas inlet 609.

[0038] When the substrate 10 is transported to the first sputtering chamber 602, a first phase shift layer 20 (ZrSiN-based layer) is formed on the surface of the substrate 10 by sputtering in the first sputtering chamber 602. Furthermore, the substrate 10 on which the first phase shift layer 20 has been formed can be transported multiple times between the buffer chamber 603 and the loading chamber 601, and sputtered multiple times in the first sputtering chamber 602 to create a layered phase shift layer 20. After that, the substrate 10 is transported to the second sputtering chamber 604. In the second sputtering chamber 604, an etching layer 30 (chromium compound layer) is formed on the surface of the phase shift layer 20 by sputtering. Similar to the ZrSiN layer, the chromium compound layer can also be transported multiple times between the buffer chamber 603 and the unloading chamber 605, and sputtered multiple times in the second sputtering chamber 604 to create a layered etching layer 30. In this way, a ZrSiN layer and a chromium compound layer are sequentially formed on the surface of the substrate 10, and a phase shift mask blank 200 is manufactured.

[0039] The materials of the first and second targets 606 and 607, and the types of gases introduced from the first and second gas inlets 608 and 609, are appropriately selected according to the materials and compositions constituting the chromium compound layer and the ZrSiN layer. Furthermore, any of the sputtering methods, such as DC sputtering, RF sputtering, or ion beam sputtering, may be used.

[0040] [Phase shift mask] The phase shift mask 300 shown in Figure 3 will now be described. The phase shift mask 300 has a substrate 10 and a phase shift layer 20 formed on the surface 10a of the substrate 10, and a predetermined pattern 50 is formed on the phase shift layer 20. The configuration of the phase shift mask 300 is the same as that of the phase shift mask blank 100 shown in Figure 1, except that a predetermined pattern 50 is formed on the phase shift layer 20. In a cross-section of the phase shift layer 20 perpendicular to the substrate surface 10a, the inclination angle θ of the side surface 21 of the phase shift layer 20 that demarcates the pattern 50 from the substrate surface 10a is preferably 45° to 90°. Furthermore, by stacking the phase shift layers 20, the inclination angle θ can be made closer to a right angle, and consequently the pattern accuracy can be improved by reducing the amount of side etching.

[0041] The method for manufacturing the phase shift mask 300 is not particularly limited, and general-purpose methods can be used. For example, the phase shift mask 300 may be manufactured using reactive sputtering and wet etching (see Figure 4), as described in the examples below.

[0042] [Exposure method] Next, we will describe an exposure method using a phase-shift mask 300 manufactured from phase-shift mask blanks 100 and 200. This exposure method using the phase-shift mask 300 can be implemented as a photolithography process using an exposure apparatus in the manufacturing of devices such as semiconductors and liquid crystal panels.

[0043] As shown in Figure 5, the exposure apparatus 500 used in the exposure method comprises a light source LS, an illumination optical system 502, a mask stage 503 that holds a phase shift mask 300, a projection optical system 504, a substrate stage 505 that holds a photosensitive substrate 515 which is the object to be exposed, and a drive mechanism 506 that moves the substrate stage 505 in a horizontal plane.

[0044] First, a phase-shift mask 300 is placed on the mask stage 503 of the exposure apparatus 500. A photosensitive substrate 515 coated with photoresist is placed on the substrate stage 505. Then, exposure light is emitted from the light source LS. The emitted exposure light is incident on the illumination optical system 502, adjusted to a predetermined light flux, and irradiated onto the phase-shift mask 300 held on the mask stage 503. The light that passes through the phase-shift mask 300 has the same pattern as the device pattern 50 drawn on the phase-shift mask 300, and this pattern is irradiated onto a predetermined position on the photosensitive substrate 515 held on the substrate stage 505 via the projection optical system 504. As a result, the photosensitive substrate 515 is exposed at a predetermined magnification by the device pattern of the phase-shift mask 300.

[0045] Phase shift mask 300, manufactured from phase shift mask blanks 100 and 200, exhibits high pattern accuracy. Therefore, using phase shift mask 300 for exposure reduces circuit pattern defects in the exposure process, enabling the efficient manufacture of highly integrated devices. [Examples]

[0046] The following describes in detail the phase shift mask blanks and phase shift masks with reference to examples and comparative examples, but the present invention is not limited to these examples and comparative examples.

[0047] As Examples 1-5, phase-shift mask blanks having five types of ZrSiN phase-shift layers 20 with different nitrogen introduction ratios were manufactured. As a comparative example, phase-shift mask blanks having two types of MoSiN phase-shift layers 20 with different nitrogen introduction ratios were manufactured.

[0048] [Manufacturing of Phase Shift Mask Blanks 100] A circular parallel plate of quartz glass was prepared as the substrate 10 (size: 3 inches in diameter, 0.5 mm thick). Using a DC magnetron sputtering apparatus, a ZrSi alloy was used as the sputtering target, and reactive sputtering was performed while introducing an Ar-N2 mixed gas at the introduction ratio shown in Table 2 to deposit a ZrSiN film on the substrate 10. Subsequently, reactive sputtering using the same ZrSi alloy target was repeated five times to form a ZrSiN-based phase shift layer 20 consisting of a total of six layers, and phase shift mask blanks 100 were manufactured (Examples 1-5). The composition (atomic ratio) of the ZrSi alloy target was Zr:Si = 1:2. The deposition conditions for each were: total pressure of mixed gas 0.32 Pa, N2 introduction ratio in the mixed gas (sputtering gas): 24% in Example 1, 26% in Example 2, 28% in Example 3, 30% in Example 4, and 60% in Example 5. The DC output was 1.5 kW for all Examples 1-5.

[0049] Comparative Example: A MoSi alloy target (atomic ratio: Mo:Si = 1:4) was used as the sputtering target, and reactive sputtering was performed once (single layer) while introducing an Ar-N2 mixed gas at the introduction ratio shown in Table 2. The N2 introduction ratio in the mixed gas (sputtering gas) was 30% in Comparative Example 1 and 36% in Comparative Example 2, and the film was deposited. Under these conditions, a MoSiN-based phase shift layer 20 was formed, and phase shift mask blanks were manufactured.

[0050] [Manufacturing of Phase Shift Mask Blanks 200] For each example and comparative example, a DC magnetron sputtering apparatus was used to perform reactive sputtering on the phase-shift mask blanks 100, using a Cr target as the sputtering target. Reactive sputtering was performed while introducing an Ar-N2 mixed gas, followed by reactive sputtering while introducing an Ar-O2 mixed gas. This formed an etching mask layer 30 consisting of a chromium nitride layer 31 and a chromium oxide layer 32 on the phase-shift mask blanks 100, thereby manufacturing phase-shift mask blanks 200 (Figure 2). The thickness of the etching mask layer 30 was deposited to be within the range of 90 ± 7 nm (thickness of chromium nitride layer 31:thickness of chromium oxide layer 32 = 7:3). Next, a positive-type ultraviolet resist (Nagase ChemteX, GRX-M237) was applied to the phase-shift mask blanks 200 by spin coating to form a photoresist layer 40 (Figure 4(A)). The thickness of the photoresist layer 40 was 660 nm.

[0051] [Evaluation of physical properties of phase-shift layer 20] Measurement of refractive index and extinction coefficient, and simulation of transmittance. For each example and comparative example, the refractive index and extinction coefficient of the phase-shift layer 20 were measured by ellipsometry. The results are shown in Table 1 and Figures 10 and 12. Furthermore, for each example and comparative example, the film thickness that gives a 180° phase shift was determined for each wavelength (365 nm, 405 nm, and 436 nm) based on the refractive index measurement results, and the transmittance of the phase-shift layer 20 at that film thickness was calculated by simulation. The results are shown in Table 1 and Figures 7 and 8. The simulation was performed using the simulation software "TFCalc," and the transmittance of the phase-shift layer 20 at each of the three wavelengths (365 nm, 405 nm, and 436 nm) was calculated using the film thickness that gives a 180° phase shift based on the refractive index and extinction coefficient measurement results at the i-line (365 nm) obtained by ellipsometry. Here, transmittance refers to the external transmittance, taking reflection into consideration.

[0052] [Manufacturing of Phase Shift Mask 300] A pattern 50 was formed on the phase shift layer 20 of each example and comparative example to produce the phase shift mask 300 shown in Figure 3. First, reactive sputtering was performed using a DC magnetron sputtering apparatus with a Cr target as the sputtering target, while introducing an Ar-N2 mixed gas, and then reactive sputtering was performed while introducing an Ar-O2 mixed gas. This formed an etching mask layer 30 consisting of a chromium nitride layer 31 and a chromium oxide layer 32 on the phase shift mask blank 100, producing a phase shift mask blank 200 (Figure 2). The thickness of the etching mask layer 30 was deposited to be within the range of 90 ± 7 nm (thickness of chromium nitride layer 31:thickness of chromium oxide layer 32 = 7:3). Next, a positive-type ultraviolet resist (Nagase ChemteX, GRX-M237) was applied to the phase shift mask blank 200 by spin coating to form a photoresist layer 40 (Figure 4(A)). The thickness of the photoresist layer 40 was 660 nm.

[0053] Using a mask aligner with a high-pressure mercury lamp (Canon, PLA-501), the photoresist layer 40 was exposed using a light-shielding mask with an opening corresponding to pattern 50. This exposed the portion of the photoresist layer 40 corresponding to pattern 50. Next, the exposed phase-shift mask blanks 200 were immersed in an organic alkaline developer (Tama Chemical Industry, 1.83% tetramethylammonium hydroxide). This dissolved and removed the photosensitive portion of the photoresist layer 40, forming an opening corresponding to pattern 50 (Figure 4(B)).

[0054] Next, using the photoresist layer 40, which had an opening corresponding to pattern 50 formed on it, as a mask, the etching mask layer 30 was wet-etched using an etching solution containing cerium ammonium nitrate and nitric acid (PureEtchCR101, manufactured by Hayashi Pure Chemical Industries). The etching solution temperature was 23±3℃ and the etching time was 80 sec. This removed the portion of the etching mask layer 30 that was not covered by the photoresist layer 40 (Figure 4(C)).

[0055] Next, using the photoresist layer 40 and etching mask layer 30, which had openings corresponding to pattern 50 formed on them, as masks, the phase shift layer 20 was wet-etched using an etching solution containing ammonium fluoride (ADEKA WGM-155). The etching solution temperature was set to 23±3℃, and 20% over-etching was performed to uniformly and completely remove the exposed phase shift layer 20. Here, 20% over-etching means that the time until the phase shift film 20 can be penetrated is used as the reference time, and etching is performed for 120% of the reference time. As a result, pattern 50 was formed on the phase shift layer 20 (Figure 4(D)).

[0056] Finally, the photoresist layer 40 and the etching mask layer 30 were removed. Through these steps, a phase shift mask 300, as shown in Figure 4(E), was obtained from the phase shift mask blanks.

[0057] [Table 1]

[0058] As shown in Table 1 and Figure 12, even with the same nitrogen introduction ratio, the extinction coefficient of the ZrSi layer in Examples 1-5 was lower than that of the MoSi layer in Comparative Examples 1 and 2. A higher extinction coefficient correlates to lower transmittance. Therefore, as shown in Table 1, Figures 7 and 8, increasing the nitrogen introduction ratio of the ZrSi phase-shift layers in Examples 1-5 and the MoSi phase-shift layers in Comparative Examples 1 and 2 increased the transmittance (365nm) of all phase-shift layers. Furthermore, even with the same nitrogen introduction ratio, the ZrSi phase-shift layer in Example 4 had a higher transmittance (365nm) than the MoSi phase-shift layer in Comparative Example 1.

[0059] As shown in Table 1 and Figure 9, the etching rate of the ZrSi phase-shift layer in Examples 1-5 was faster than the etching rate of the MoSi phase-shift layer in Comparative Examples 1 and 2. Furthermore, since the refractive index of the ZrSi phase-shift layer in Examples 1-5 is higher than that of the MoSi phase-shift layer in Comparative Examples 1 and 2, the film thickness of the ZrSi phase-shift layer at a phase of 180° in Examples 1-5 was thinner than that of the MoSi phase-shift layer in Comparative Examples 1 and 2.

[0060] During the manufacturing process of the phase shift mask 300, cross-sectional observations were performed on the patterns 50 formed in each example and comparative example. The cross-sectional observations were performed before the etching mask layer 30 and the photoresist layer 40 were removed (as shown in Figure 4(D)). Figure 13 shows SEM images of the cross-sections perpendicular to the substrate surface 10a for each example and comparative example. From Figure 13, the inclination angle θ of the side surface 21 of the phase shift layer 20 from the substrate surface 10a was measured for each example and comparative example. The results are shown in Table 1 and Figure 13.

[0061] Table 1 and Figure 13 show that the tilt angle of the ZrSi layer in Examples 1-5 is greater than the tilt angle of the MoSi layer in Comparative Examples 1 and 2. Furthermore, in Comparative Example 2, it can be seen that the substrate 10 was also etched due to the longer etching time. Additionally, as shown in Table 1 and Figure 11, even with the same nitrogen introduction ratio, the tilt angle of the ZrSi layer in Example 4 was greater than the tilt angle of the MoSi layer in Comparative Example 1.

[0062] Furthermore, the inclination angle of the phase-shift layer 20 of this embodiment, which has been 20% over-etched under the conditions of an etching solution containing ammonium fluoride (ADEKA, ADEKA Cerumica WGM-155, etching solution temperature 23±3℃), is preferably 55° or more and 90° or less. The preferred lower limit is 58°, more preferably 60°, and even more preferably 65°.

[0063] During the manufacturing process of the phase shift mask 300, cross-sectional observations were performed on the patterns 50 formed on the ZrSiN phase shift layers 20, which were deposited in 4, 6, and 8 layers, respectively. The nitrogen introduction ratio during the deposition of the ZrSiN film was 28%, the same as in Example 3. Cross-sectional observations were performed before the etching mask layer 30 and the photoresist layer 40 were removed (as shown in Figure 4(D)). Figure 14 shows SEM images of cross-sections perpendicular to the substrate surface 10a, and sketches drawn based on the SEM images, for phase shift masks having (A) 4 layers, (B) 6 layers, and (C) 8 layers of shift layers 20. Figure 14(B) shows a film deposited under the same conditions as in Example 3, but with a longer etching time than in Example 3. From the side surfaces 21 of the phase shift layers 20 in Figures 14(A) to (C), it can be confirmed that the phase shift layers 20 are stacked. [Industrial applicability]

[0064] The phase-shift mask blanks according to this embodiment have a shorter etching time and a higher refractive index than MoSi phase-shift mask blanks, which allows for thinner film thickness when the phase shift is 180°, and improves pattern accuracy by reducing the amount of side etching. [Explanation of Symbols]

[0065] 10 circuit boards 20 Phase-shifted layers 30 Etching mask layer 31 Chromium nitride layer 32 Chromium oxide layer 40 Photoresist layer 50 patterns 100,200 Phase Shift Mask Blanks 300 Phase Shift Masks 500 exposure equipment LS light source 502 Illumination optical system 504 Projection optical system 503 Mask Stage 505 PCB Stage 600 Film deposition equipment 600 P Circuit Board Tray Q Solid arrow R (dotted arrow) 601 Loading Chamber 602 First sputtering chamber 603 Buffer Chamber 604 Second sputtering chamber 605 Exhaust Chamber 606 First target (ZrSi) 607 Second Target (Cr) 608 First gas inlet 609 Second gas inlet

Claims

1. Phase shift mask blanks, circuit board and It comprises a first layer formed on the substrate, The first layer comprises zirconium (Zr), silicon (Si), and nitrogen (N). The transmittance per unit thickness of the first layer that causes a 180° phase shift to light with a wavelength of 365 nm is 4% or more and 40% or less. Phase-shift mask blanks.

2. Phase shift mask blanks, circuit board and It comprises a first layer formed on the substrate, The first layer is a laminate having four or more layers of nitride of a metal silicide containing zirconium (Zr) and silicon (Si), The transmittance per unit thickness of the first layer that causes a 180° phase shift to light with a wavelength of 365 nm is 4% or more and 40% or less. Phase-shift mask blanks.

3. Phase shift mask blanks, circuit board and It comprises a first layer formed on the substrate, The first layer is a laminate having four or more layers of nitride of a metal silicide containing zirconium (Zr) and silicon (Si), The inclination angle of the first layer is 55° or more and 90° or less. Phase-shift mask blanks.

4. The phase-shift mask blank according to any one of claims 1 to 3, wherein the transmittance per unit thickness of the first layer that gives a phase shift of 180° to light with a wavelength of 365 nm is 4% or more and 40% or less.

5. The phase shift mask blank according to any one of claims 1 to 4, wherein the inclination angle is the angle when the first layer is over-etched by 20% under the condition that the etching solution is Adeka Cerumica WGM-155 and the temperature of the etching solution is 23±3°C.

6. The film thickness at which light with a wavelength of 365 nm in the first layer causes a 180° phase shift is the film thickness calculated by the following formula (1): d=365 / (2(n-1)) (d: film thickness, n: refractive index) A phase-shift mask blank according to claim 1 or 2.

7. A phase shift mask having a desired pattern formed on a phase shift mask blank as described in any one of claims 1 to 6.

8. A method for manufacturing phase-shift mask blanks, The process includes a film deposition step of forming a first layer on a substrate. A method for manufacturing phase-shift mask blanks, comprising the film formation step of forming a first layer by depositing a nitride layer of a metal silicide containing zirconium and silicon on the substrate four or more times.

9. The method for manufacturing a phase-shift mask blank according to claim 8, wherein in the film deposition step, a nitride layer of the metal silicide is deposited on the substrate six or more times.

10. A method for manufacturing a phase shift mask, The method for manufacturing a phase-shift mask blank according to claim 8 or claim 9 further comprises a pattern forming step of forming a desired pattern. A method for manufacturing a phase shift mask.

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