Phase shift mask, detection element, defocus amount detection method, focus adjustment method, and device manufacturing method

Abstract

Provided is a phase shift mask (100, 200) comprising: a substrate (10); a first semitransparent layer (20); a second semitransparent layer (20); and a light-shielding layer (30), wherein, on the surface of the substrate, a measurement mark is formed having a pattern in which a first region (A1) having the first semitransparent layer disposed therein, a second region (B1) having the surface of the substrate exposed therein, a third region (C) having the light-shielding layer disposed therein, a fourth region (A2) having the second semitransparent layer disposed therein, and a fifth region (B2) having the surface of the substrate exposed therein are provided adjacent to each other along an arrangement direction parallel to the surface of the substrate.

Description

[Technical Field]

[0001] The present invention relates to a phase shift mask, a detection element, a defocus amount detection method, a focus adjustment method, and a device manufacturing method. [Background technology]

[0002] In the lithography process, which is one of the manufacturing processes for devices such as semiconductor elements, liquid crystal display elements, imaging devices (CCD, etc.), and thin-film magnetic heads, a projection exposure apparatus is used to transfer the pattern of a reticle (mask) onto a wafer or glass plate (hereinafter referred to as a photosensitive substrate) coated with photoresist via a projection optical system. In device manufacturing, it is important to perform exposure without image blurring or color unevenness of the pattern due to defocus.

[0003] A PSFM (Phase Shift Focus Monitor) is known as a means for evaluating the focus performance of a projection exposure apparatus (see, for example, Patent Document 1). In the evaluation method described in Patent Document 1, exposure is first performed using a phase shift mask on which measurement marks are formed. At this time, a phenomenon occurs in which a pattern image formed when exposure is performed in a defocused state is displaced (moved) laterally (in a plane perpendicular to the optical axis of the projection optical system) relative to the pattern image formed when exposure is performed in a focused state. This phenomenon is utilized to convert the amount of displacement into a defocus amount and evaluate the focus performance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 5,300,786 Summary of the Invention

[0005] According to a first aspect, there is provided a phase shift mask having a substrate, first and second semi-transmitting layers (first and second phase shift films), and a light-shielding layer (light-shielding film), and on the surface of the substrate, along an arrangement direction parallel to the surface, a measurement mark having a pattern in which a first region in which the first semi-transmitting layer (first phase shift film) is arranged, a second region in which the substrate surface is exposed, a third region in which the light-shielding layer (light-shielding film) is arranged, a fourth region in which the second semi-transmitting layer (second phase shift film) is arranged, and a fifth region in which the substrate surface is exposed are arranged adjacent to each other.

[0006] According to a second aspect, there is provided a detection element for detecting the defocus amount of light of a predetermined wavelength that passes through a projection optical system, the detection element having a substrate, first and second semi-transparent layers (first and second phase shift films), and a light-shielding layer (light-shielding film), and on the surface of the substrate, along an arrangement direction parallel to the surface, a measurement mark having a pattern in which a first region in which the first semi-transparent layer (first phase shift film) is arranged, a second region in which the substrate surface is exposed, a third region in which the light-shielding layer (light-shielding film) is arranged, a fourth region in which the second semi-transparent layer (second phase shift film) is arranged, and a fifth region in which the substrate surface is exposed are arranged adjacent to each other.

[0007] According to a third aspect, there is provided a method for detecting a defocus amount of a projection optical system using the phase shift mask of the first aspect or the detection element of the second aspect, the method including: irradiating the phase shift mask or the detection element with light of a predetermined wavelength to form a projected image of the measurement mark by the projection optical system on a projection surface; measuring a positional deviation amount of the projected image of the measurement mark from a predetermined position on the projection surface; and calculating the defocus amount from the measured positional deviation amount.

[0008] According to a fourth aspect, there is provided a focus adjustment method for a projection optical system, which includes detecting a defocus amount of the projection optical system by the defocus amount detection method of the third aspect, and adjusting the focus of the projection optical system based on the detected defocus amount.

[0009] According to a fifth aspect, there is provided a method for manufacturing a device, which includes exposing a photosensitive substrate with a predetermined pattern using the projection optical system adjusted by the focus adjustment method of the fourth aspect. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1(a) is a schematic diagram of the underside of a phase shift mask having measurement marks according to an embodiment (as viewed from the surface on which the measurement marks are formed), and FIG. 1(b) is a schematic diagram of a cross section taken along line IB-IB in FIG. 1(a). [Figure 2] FIG. 2(a) is an enlarged view of the IIA area in FIG. 1(a), and FIG. 2(b) is a schematic view of the cross section taken along line IIB-IIB in FIG. 2(a). [Figure 3] Fig. 3(a) is a diagram showing a projected image of a measurement mark (box-in-box pattern) in an embodiment when in focus (defocus amount is 0 (zero)), Fig. 3(b) is a diagram showing a projected image of a measurement mark when out of focus (defocus amount is not 0 (zero)), and Fig. 3(c) is a diagram showing the relationship between the defocus amount and the shift amount in an embodiment. [Figure 4] FIG. 4 is a flowchart showing a defocus amount detection method and a focus adjustment method according to the embodiment. [Figure 5] FIG. 5 is a schematic diagram of an exposure apparatus that performs defocus amount detection and focus adjustment according to an embodiment. [Figure 6]Fig. 6(a) is a schematic diagram of a phase shift mask provided with a plurality of measurement marks in a modified example, Fig. 6(b) is a schematic diagram of a photosensitive substrate on which the plurality of measurement marks are exposed, Fig. 6(c) is a diagram showing the amount of defocus on the photosensitive substrate before focus adjustment in a modified example, and Fig. 6(d) is a diagram showing the amount of defocus on the photosensitive substrate after focus adjustment. [Figure 7] FIG. 7 is a table showing gas flow rates and composition ratios during deposition of the phase shift films PS1 to PS14. [Figure 8] FIG. 8 is a table showing the film thicknesses of the phase shift films PS1 to PS14 and their optical characteristics with respect to light having a wavelength of 302 nm. [Figure 9] FIG. 9 is a table showing the film thicknesses of the phase shift films PS1 to PS14 and their optical characteristics with respect to light having a wavelength of 313 nm. [Figure 10] FIG. 10 is a table showing the film thicknesses of the phase shift films PS1 to PS14 and their optical characteristics with respect to light having a wavelength of 334 nm. [Figure 11] FIG. 11 is a table showing the film thicknesses of the phase shift films PS1 to PS14 and their optical characteristics with respect to light having a wavelength of 365 nm. [Figure 12] FIG. 12 is a table showing the film thicknesses of the phase shift films PS1 to PS14 and their optical characteristics with respect to light having a wavelength of 405 nm. [Figure 13] FIG. 13 is a table showing the film thicknesses of the phase shift films PS1 to PS14 and their optical characteristics with respect to light having a wavelength of 436 nm. [Figure 14] 14(a) to 14(f) are diagrams illustrating a method for manufacturing a phase shift mask having measurement marks according to an embodiment. [Figure 15] 15(a) to 15(f) are diagrams illustrating a method for manufacturing a phase shift mask having measurement marks according to an embodiment. [Figure 16] FIG. 16 shows the results of a simulation of the relationship between the shift amount and the defocus amount performed in the example. [Figure 17]Figure 17(a) is a diagram showing a cross pattern measurement mark, Figure 17(b) is a diagram showing a projected image of the measurement mark when in focus (defocus amount is 0 (zero)), and Figure 17(c) is a diagram showing a projected image of the measurement mark when out of focus (defocus amount is not 0 (zero)). [Figure 18] FIG. 18 shows a phase shift mask with measurement marks that does not have a phase shift film. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Phase shift mask] A phase shift mask 100 having a measurement mark 40 shown in FIG. 1 will be described. The phase shift mask 100 is used, for example, as a detection element for detecting the defocus amount of light (exposure light) of a predetermined wavelength that passes through a projection optical system mounted in a projection exposure apparatus. The phase shift mask 100 has a substrate 10, a light-shielding film (light-shielding layer) 30 formed on a surface (substrate surface) 10a of the substrate 10, and a phase shift film (semi-transmitting film / semi-transmitting layer) 20 formed on the substrate surface 10a. The phase shift film 20 is formed near the light-shielding film 30. The light-shielding film 30 constitutes the measurement mark 40. In this embodiment, a so-called box-in-box pattern consisting of a pair of concentric squares (or rectangles) is used as the measurement mark 40. Details of the measurement mark 40 used in this embodiment will be described later.

[0012] The basic arrangement of the phase shift film 20 and the light-shielding film 30 on the substrate surface 10a will be described. As shown in FIG. 2, along the X direction that intersects the phase shift film 20 and the light-shielding film 30, regions A1, B1, C, A2, and B2 are arranged adjacent to each other on the substrate surface 10a. The phase shift film 20 is arranged in regions A1 and A2. The phase shift film 20 is not present in regions B1 and B2, and the substrate surface 10a is exposed. The light-shielding film 30 is arranged in region C. The measurement mark 40 includes at least region C and may also include regions A1, A2, B1, and B2 in addition to region C. When light (exposure light) of a predetermined wavelength is irradiated onto the phase shift mask, the phases of the light (first light) transmitted through regions A1 and A2 are the same, and the phases of the light (second light) transmitted through regions B1 and B2 are the same. On the other hand, because the phase shift film 20 is formed, the phase of light transmitted through regions A1 and A2 is shifted and differs from the phase of light transmitted through regions B1 and B2. Regions A1, B1, C, A2, and B2 in this embodiment correspond to the "first region," "second region," "third region," "fourth region," and "fifth region" of the present invention, respectively. The "X direction" in this embodiment corresponds to the "arrangement direction" of the present invention. The phase shift film 20 arranged in region A1 corresponds to the "first phase shift film," "first semi-transmitting layer," or "first semi-transmitting film," while the phase shift film 20 arranged in region A2 corresponds to the "second phase shift film," "second semi-transmitting layer," or "second semi-transmitting film." Furthermore, the basic arrangement of the phase shift film 20 and the light-shielding film 30 in this embodiment (regions A1, B1, C, A2, and B2) corresponds to the "pattern" of the present invention.

[0013] When a phase-shifting material is placed on the measurement mark, the projected image of the measurement mark on the projection surface via the projection optical system shifts in position within the projection plane perpendicular to the optical axis of the projection optical system according to the amount of defocus. In the phase shift mask 100 of this embodiment, the light-shielding film 30 forming the measurement mark 40 and the phase shift film 20 have a unique basic arrangement (areas A1, B1, C, A2, B2) as described above. This unique basic arrangement strengthens the correlation between the amount of defocus of the projected image of the measurement mark 40 and the amount of misalignment on the projection surface, enabling easy and accurate detection of the amount of defocus using the phase shift mask 100. As a result, focus adjustment is simplified. The reason for this is presumably related to interference between light transmitted through area A1 and light transmitted through area B1 on one side of the mark-forming area C, and interference between light transmitted through area A2 and light transmitted through area B2 on the other side of area C.

[0014] When the phase shift mask is irradiated with light (exposure light) of a predetermined wavelength, the phase difference between the first light transmitted through regions A1 and A2 where the phase shift film is disposed and the second light transmitted through regions B1 and B2 where the substrate surface 10a is exposed is 90°±50°, preferably 90°±20°, more preferably 90°±5°, and even more preferably 90°±3°. A phase difference within this range facilitates detection of the defocus amount and focus adjustment using the phase shift mask 100. The phase difference can be adjusted by changing the refractive index, film thickness, etc. of the phase shift film to match the wavelength of the light (exposure light) transmitted through the phase shift mask 100. That is, the phase shift film 20 is preferably configured so that the phase difference is within the above range.

[0015] In the phase shift mask 100, the width Wb1 of the region B1 and the width Wa2 of the region A2 in the X direction are smaller than the width Wc of the region C (Wc>Wb1, Wc>Wa 2)The ratio (Wb1 / Wc) of width Wb1 to width Wc is preferably 0.1 to 0.2, more preferably 0.1 to 0.15, and even more preferably 0.1 to 0.13. The ratio (Wa2 / Wc) of width Wa2 to width Wc is preferably 0.1 to 0.2, more preferably 0.1 to 0.15, and even more preferably 0.1 to 0.13. Widths Wb1 and Wa2 may be approximately the same (Wb1=Wa2). Widths Wb1 and Wa2 may be smaller than width Wa1 of region A1. Furthermore, width Wa1 is preferably at least twice width Wc. When widths Wa1, Wb1, Wc, and Wa2 have the above-mentioned relationship, detection of the defocus amount and focus adjustment become easier.

[0016] The widths Wa1, Wb1, Wc, and Wa2 can be appropriately designed taking into consideration the wavelength of the exposure light of the projection exposure tool in which the phase shift mask 100 is used.

[0017] The measurement mark 40 of this embodiment may have any shape as long as it includes a portion where straight lines face each other. Furthermore, the measurement mark 40 (light-shielding film 30) may include a straight line portion, and the X direction crossing the pattern formed by the light-shielding film 30 may be a direction perpendicular to the direction in which the straight line portion extends. In this case, the width of each region is the width (length) in the direction perpendicular to the direction in which the straight line portion extends.

[0018] The material of the substrate 10 is not particularly limited as long as it sufficiently transmits the exposure light of the projection exposure apparatus in which the phase shift mask 100 is used. For example, quartz glass may be used. The thickness of the substrate 10 may be, for example, 5 mm to 30 mm, or 7 mm to 20 mm.

[0019] The material of the light-shielding film 30 is not particularly limited as long as it sufficiently blocks exposure light from a projection exposure apparatus in which the phase shift mask 100 is used. For example, a metal such as chromium may be used. Specific examples include chromium oxide (CrO) and chromium nitride (CrN). The thickness of the light-shielding film 30 is, for example, 50 nm to 300 nm, with a preferred lower limit of 80 nm, a more preferred lower limit of 100 nm, and a preferred upper limit of 200 nm, and a more preferred upper limit of 150 nm. Furthermore, as shown in FIG. 2(b), a phase shift film 20 may be present below the light-shielding film 30. In this embodiment, the phase shift film 20 is continuously formed over the regions C and A2 on the substrate surface 10a, and the light-shielding film 30 is stacked on the phase shift film 20 in the region C. That is, a layered structure of the phase shift film 20 and the light-shielding film 30 is formed in the region C. Even with this layered structure, the light-shielding film 30 sufficiently blocks light from the region C. Furthermore, with such a laminated structure, the entire formation mark 40 can be easily formed by wet etching, which will be described later. Note that, in the region C, the phase shift film 20 may not be formed, and only the light-shielding film 30 may be formed.

[0020] The phase shift film 20 shifts (changes) the phase of light transmitted through it. The phase shift film 20 may be, for example, a film containing zirconium (Zr), silicon (Si), and nitrogen (N). In the phase shift mask 100, interference between light transmitted through regions A1 and A2 and light transmitted through regions B1 and B2 is required, so the phase shift film 20 must transmit the exposure light. The phase shift film 20 containing Zr, Si, and N sufficiently transmits light with wavelengths of, for example, 250 nm to 440 nm. Furthermore, as will be described later, the measurement marks 40 formed in regions A1 and A2 by the phase shift film 20 containing Zr, Si, and N exhibit a linear relationship between the defocus amount and the shift amount over a wide range (see FIG. 3(c)). As a result, detection of the defocus amount and focus adjustment using the phase shift mask 100 can be performed more easily and accurately.

[0021] Furthermore, the phase shift film 20 may further contain oxygen (O) in addition to zirconium (Zr), silicon (Si), and nitrogen (N). By including oxygen (O), the phase shift film 20 has a higher transmittance for light with wavelengths of 250 nm to 440 nm. As a result, the defocus amount and shift amount in the measurement marks 40 (described later) exhibit a linear relationship over a wider range (see FIG. 3(c)). As a result, detection of the defocus amount and focus adjustment using the phase shift mask 100 can be performed more easily and accurately.

[0022] To achieve a transmittance of 25% or more for light with wavelengths of 250 nm to 400 nm through the phase shift film 20, the preferred compositions of the phase shift film 20 are described below for the following two cases (i) and (ii). (i) When the atomic ratio (O / Zr) of the phase shift film 20 is less than 0.1, the atomic ratio (N / Zr) is preferably 2.0 or more. (ii) When the atomic ratio (O / Zr) of the phase shift film is 0.1 or more, the atomic ratio (N / Zr) is preferably in the range of 0 to 3.0. In both cases (i) and (ii), the atomic ratio (Si / Zr) is preferably 0.5 to 2.0 or 0.8 to 1.2.

[0023] The phase shift film 20 may contain elements other than Zr, Si, N, and O, or may be a film containing substantially only Zr, Si, N, and O. The phase shift film 20 may contain no elements other than Zr, Si, N, and O, or may contain small amounts of impurities that do not affect the effect. In this specification, the atomic ratio of the phase shift film 20 can be measured using X-ray photoelectron spectroscopy (XPS), which will be described in the examples below.

[0024] The higher the refractive index of the phase shift film 20, the more preferable. The reasons for this are as follows: A higher refractive index allows the thickness of the phase shift film 20, calculated by the formula d=λ / (2(n-1)) (d: thickness of the phase shift film 20, λ: wavelength of the exposure light, n: refractive index of the phase shift film 20 at wavelength λ), to be reduced. Reducing the thickness required for film formation allows the film to be formed more uniformly on the substrate 10. Furthermore, if the film thickness can be reduced, the amount of so-called side etching can be reduced, resulting in a pattern closer to the design dimensions.

[0025] The lower the extinction coefficient (attenuation coefficient) of the phase shift film 20, the more preferable it is. The reason for this is that a lower extinction coefficient reduces light absorption, and the transmittance of the phase shift film 20 improves.

[0026] The refractive index of the phase shift film 20 for light with a wavelength of 302 nm is 1.7 to 3.0, with a preferred lower limit of 1.75 and a preferred upper limit of 2.9. The attenuation coefficient of the phase shift film 20 for light with a wavelength of 302 nm is 0.6 or less, with a preferred lower limit of 10 -6 and the preferred upper limit is 0.55. Here, the transmittance of the portion of the phase shift mask 100 where the phase shift film 20 is formed on the substrate 10 is referred to as the "element transmittance," which is also referred to as the external transmittance taking reflection into consideration. The "element transmittance" is the transmittance of the substrate 10 and the phase shift film 20. When the phase shift film 20 has a thickness that imparts a phase shift of 180° to light with a wavelength of 302 nm, the element transmittance for light with a wavelength of 302 nm is preferably 25% or more, and more preferably 40% or more. End is preferable, and 60% or more is more preferable.

[0027] The refractive index of the phase shift film 20 for light with a wavelength of 313 nm is 1.7 to 3.0, with a preferred lower limit of 1.75 and a preferred upper limit of 2.9. The attenuation coefficient of the phase shift film 20 for light with a wavelength of 313 nm is 0.5 or less, with a preferred lower limit of 10 -6The upper limit is preferably 0.45. Furthermore, when the phase shift film 20 has a thickness that gives a phase shift of 180° to light with a wavelength of 313 nm, the element transmittance for light with a wavelength of 313 nm is preferably 30% or more, and more preferably 40% or more. End is preferable, and 60% or more is more preferable.

[0028] The refractive index of the phase shift film 20 for light with a wavelength of 334 nm is 1.7 to 3.0, with a preferred lower limit of 1.75 and a preferred upper limit of 2.9. The attenuation coefficient of the phase shift film 20 for light with a wavelength of 334 nm is 0.4 or less, with a preferred lower limit of 10 -6 The upper limit is preferably 0.35. Furthermore, when the phase shift film 20 has a thickness that gives a phase shift of 180° to light with a wavelength of 334 nm, the element transmittance for light with a wavelength of 334 nm is preferably 40% or more, and more preferably 50% or more. End is preferable, and 70% or more is more preferable.

[0029] The refractive index of the phase shift film 20 for light with a wavelength of 365 nm is 1.7 to 3.0, with a preferred lower limit of 1.72 and a preferred upper limit of 2.85. The attenuation coefficient of the phase shift film 20 for light with a wavelength of 365 nm is 0.2 or less, with a preferred lower limit of 10 -6 The upper limit is preferably 0.18. Furthermore, when the phase shift film 20 has a thickness that gives a phase shift of 180° to light with a wavelength of 365 nm, the element transmittance for light with a wavelength of 365 nm is preferably 50% or more, and more preferably 60% or more. End is preferable, and 70% or more is more preferable.

[0030] As described above, the phase shift film 20 preferably has a high transmittance for light with a wavelength of 250 nm to 440 nm, which is used as exposure light in a projection exposure apparatus. Typical examples of exposure light include deep ultraviolet (DUV, wavelengths: 302 nm, 313 nm, 334 nm), i-line (wavelength: 365 nm), h-line (wavelength: 405 nm), and g-line (wavelength: 436 nm). For example, the transmittance for light with a wavelength of 250 nm to 440 nm in the first and fourth regions where the phase shift film 20 is disposed is preferably 25% or higher, more preferably 30% or higher, and even more preferably 40% or higher. The transmittances for the first and fourth regions correspond to the aforementioned element transmittance.

[0031] The thickness of the phase shift film 20 can be designed so that the phase difference between the light transmitted through regions A1 and A2 and the light transmitted through regions B1 and B2 falls within an appropriate range (e.g., 90°±50°) in consideration of the optical properties of the phase shift film 20, such as the refractive index, and the wavelength of the light (exposure light) transmitted through it. For example, the thickness of the phase shift film 20 may be 40 nm to 150 nm.

[0032] As described above, in this embodiment, the phase shift film 20 is provided in the regions A1 and A2, thereby generating a phase difference between the first light beam passing through the regions A1 and A2 and the second light beam passing through the regions B1 and B2. Alternatively, instead of providing the phase shift film 20, a similar phase difference can be generated by thinning the regions B1 and B2 of the substrate 10 and providing a height difference (step) on the substrate surface 10a, as shown in FIG. 18 . However, the step provided on the substrate surface 10a is determined by the wavelength of the exposure light. For example, to obtain a phase difference of 90° using exposure light with a wavelength of 365 nm, the step provided on the substrate surface 10a made of quartz glass (refractive index: 1.47) is 192 nm. The step on the substrate surface 10a is formed, for example, by etching, but it is very difficult to uniformly etch a 192 nm step. A decrease in the accuracy of the step processing leads to a decrease in the accuracy of defocus detection for the phase shift mask. In particular, the larger the area to be etched, that is, the larger the area of ​​the phase shift mask and the greater the number of measurement marks 40, the more pronounced this problem becomes.

[0033] In the phase shift mask 100 of this embodiment, the phase shift film 20 is formed without forming steps on the substrate surface 10a. It is relatively easy to form the phase shift film 20 with a uniform thickness over a large area. Therefore, even if the phase shift mask 100 is enlarged and the number of measurement marks 40 increases, the accuracy of defocus detection can be improved. For example, large phase shift masks are required for the manufacture of large-area devices such as flat panel displays (FPDs). The phase shift mask 100 of this embodiment can be suitably used in the manufacture of large-area devices such as FPDs.

[0034] [Method of manufacturing phase shift masks] There are no particular limitations on the method for manufacturing phase shift mask 100 having measurement marks 40, and a general-purpose method can be used. For example, phase shift mask 100 may be manufactured by forming measurement marks 40 using reactive sputtering and wet etching (see FIGS. 14 and 15).

[0035] An example of a method for manufacturing a phase shift mask shown in Figures 14 and 15 will be described. First, a phase shift mask blank 150 is prepared, which has a substrate 10 and a phase shift film 20 formed on a substrate surface 10a (Figure 14(a)). The phase shift mask blank 150 may be manufactured, for example, by forming the phase shift film 20 on the substrate surface 10a by reactive sputtering.

[0036] Next, the measurement marks 40 are formed (patterned). The measurement marks 40 may be formed by, for example, wet etching. First, a Cr film is formed as the light-shielding film 30 on the phase shift film 20 by reactive sputtering. Here, the light-shielding film 30 may be formed by laminating a chromium nitride layer 31 and a chromium oxide layer 32 (not shown). A resist is applied onto the light-shielding film 30 by spin coating to form a first photoresist layer 51 (FIG. 14(b)). Note that although FIG. 14 shows an embodiment using a positive resist, a negative resist may also be used.

[0037] Using a first light-shielding mask, the first photoresist layer 51 is exposed to light of a predetermined wavelength. The predetermined wavelength of light is not particularly limited, and may be light of a wavelength to which the resist is sensitive, such as light of 365 nm. The first light-shielding mask has a pattern formed thereon that covers areas A1, A2, and C on the substrate surface 10a and exposes areas B1 and B2. As a result, the first photoresist layer 51 in areas B1 and B2 is exposed, forming first exposed portions 51E (FIG. 14(c)).

[0038] The exposed substrate 10 is immersed in a developer, which dissolves and removes the first photosensitive portion 51E (FIG. 14(d)). Next, the substrate 10 is immersed in an etching solution for the light-shielding film 30. This removes the light-shielding film 30 on the regions B1 and B2 that are not covered with the first photoresist layer 51, exposing the phase shift film 20 (FIG. 14(e)).

[0039] The substrate 10 is immersed in an etching solution for the phase shift film 20. This removes the phase shift film 20 on the regions B1 and B2 that are not covered with the first photoresist layer 51, exposing the substrate surface 10a (FIG. 14(f)).

[0040] Next, the substrate 10 is immersed in a resist remover. This dissolves and removes all of the first photoresist layer 51 remaining on the substrate 10 (FIG. 15(a)). After the first photoresist layer 51 is removed, a second photoresist layer 52 is formed on the entire substrate surface 10a (FIG. 15(b)). The second photoresist layer 52 may be formed using the same material and method as the first photoresist layer 51, and may have the same thickness.

[0041] Using a second light-shielding mask, the second photoresist layer 52 is exposed to light of a predetermined wavelength. The second light-shielding mask has a pattern formed thereon that exposes the regions A1 and A2 on the substrate surface 10a. As a result, the second photoresist layer 52 in the regions A1 and A2 is exposed, and second exposed portions 52E are formed (FIG. 15(c)).

[0042] The exposed substrate 10 is immersed in a developer, thereby dissolving and removing the second exposed portion 52E (FIG. 15(d)). Next, the substrate 10 is immersed in an etching solution for the light-shielding film 30, thereby removing the light-shielding film 30 on the regions A1 and A2, and exposing the phase shift film 20 (FIG. 15(e)). Next, the substrate 10 is immersed in a resist stripper, thereby dissolving and removing all of the second photoresist layer 52 remaining on the substrate 10 (FIG. 15(f)). Through the above steps, a phase shift mask 100 can be obtained, on which the measurement marks 40 shown in FIG. 15(f) are formed. Note that, although wet etching shown in FIGS. 14 and 15 has been described as a method for patterning the measurement marks 40, this embodiment is not limited to this, and the measurement marks 40 may be patterned using a known method.

[0043] [Measurement mark structure and operating principle] The structure of the measurement mark 40 used in this embodiment, shown in FIG. 1, will be described. As shown in FIG. 1(a), the measurement mark 40 is a "box-in-box" pattern consisting of two approximately rectangular shapes. The measurement mark 40 is composed of an outer rectangle (first mark) 41 and an inner rectangle (second mark) 42 arranged within and concentric with the outer rectangle 41. The outer rectangle 41 is larger than the inner rectangle 42. The outer rectangle 41 includes, on the substrate surface 10a, horizontal sides 411x and 412x extending in the X direction (an example of a "first arrangement direction") parallel to the substrate surface 10a, and vertical sides 411y and 412y extending in the Y direction (an example of a "second arrangement direction") parallel to the substrate surface 10a and perpendicular to the X direction. The horizontal sides 411x and 412x and the vertical sides 411y and 412y may be joined to form a complete rectangle, or may be separated in part or in whole to form an incomplete rectangle. In this embodiment, as shown in FIG. 1(a), the outer rectangle 41 is an incomplete rectangle.

[0044] On the substrate surface 10a, the inner rectangle 42 includes horizontal sides 421x and 422x extending in the X direction and vertical sides 421y and 422y extending in the Y direction. The horizontal sides 421x and 422x and the vertical sides 421y and 422y may be joined to form a complete rectangle, or may be partially or entirely spaced apart to form an incomplete rectangle. In this embodiment, as shown in FIG. 1(a), the inner rectangle 42 is an incomplete rectangle.

[0045] 1(b), near the vertical sides 411y and 412y of the outer rectangle 41 and near the vertical sides 421y and 422y of the inner rectangle 42, regions A1, B1, C, A2, and B2 are arranged adjacent to each other in this order along the X direction crossing the phase shift film 20 and the light-shielding film 30. That is, the measurement mark 40 has the basic arrangement of the phase shift film 20 and the light-shielding film 30 described above. However, the orientation of the basic arrangement is the same near the vertical side 411y and near the vertical side 412y, but is opposite near the vertical side 412y and near the vertical side 422y. The orientation of the basic arrangement is opposite near the vertical side 411y and near the vertical side 421y. On vertical sides 411y and 412y (outer rectangle 41), regions A1, B1, C, A2, and B2 are arranged adjacent to each other in this order in a direction X1 from one side to the other in the X direction (from left to right in FIG. 1(b)). On the other hand, on vertical sides 421y and 422y (inner rectangle 42), regions A1, B1, C, A2, and B2 are arranged adjacent to each other in this order in a direction X2 from the other side to one side in the X direction (from right to left in FIG. 1(b)).

[0046] Near the horizontal sides 411x and 412x of the outer rectangle 41 and the horizontal sides 421x and 422x of the inner rectangle 42, regions A1, B1, C, A2, and B2 are arranged adjacent to each other in this order along the direction Y that crosses the phase shift film 20 and the light-shielding film 30, but the arrangement directions are reversed. On the horizontal sides 411x and 412x (outer rectangle 41), regions A1, B1, C, A2, and B2 are arranged adjacent to each other in this order in the direction Y1 from one side to the other in the Y direction (the direction from bottom to top in FIG. 1(b)). On the other hand, in horizontal sides 421x and 422x (inner rectangle 42), regions A1, B1, C, A2, and B2 are arranged adjacent to each other in this order in the direction Y2 from the other side to the one side of the Y direction (from top to bottom in Figure 1(b)).

[0047] In this embodiment, as shown in FIG. 1B, the outer rectangle 41 (vertical side 411y) and the inner rectangle 42 (vertical side 421y) share the region B2 between them as the B2 of their respective basic arrangements. The outer rectangle 41 (vertical side 412y) and the inner rectangle 42 (vertical side 422y) share the region A1 between them as the A1 of their respective basic arrangements. This reduces the space required for the mark 40. The width Wb2 of the region B2 between the outer rectangle 41 and the inner rectangle 42 must be large enough to resolve the aerial images of the regions C included in the outer rectangle 41 and the inner rectangle 42 when projecting exposure light onto the measurement mark 40 (phase shift mask 200). Therefore, it is preferable that the width Wb2 of the region B2 be at least twice the width Wc of the region C of the outer rectangle 41 or at least twice the width Wc of the region C of the inner rectangle 42. Note that vertical side 411y (first pattern), vertical side 421y (second pattern), vertical side 422y (third pattern), and vertical side 412y (fourth pattern) are referred to as the first part, and horizontal side 411x (fifth pattern), horizontal side 421x (sixth pattern), horizontal side 422x (seventh pattern), and horizontal side 412x (eighth pattern) are referred to as the second part.

[0048] In this way, the arrangement directions of regions A1, B1, C, A2, and B2 in the X direction are opposite to those of the inner rectangle 41 and the inner rectangle 42, and the arrangement directions of the same regions in the Y direction are also opposite to those of the outer rectangle 41 and the inner rectangle 42. Projected images of the outer rectangle 41 and the inner rectangle 42 via the projection optical system are shifted in opposite directions on the same straight line within the projection plane depending on the defocus amount.

[0049] For example, as shown in Fig. 3(a), when the projection optical system is in focus, that is, when the defocus amount is 0 (zero), in a projected image 40P on the projection surface of the measurement mark 40 via the projection optical system, a center 41C of a projected image 41P of an outer rectangle 41 coincides with a center 42C of a projected image 42P of an inner rectangle 42. On the other hand, as shown in Fig. 3(b), when the projection optical system is out of focus, that is, when defocus occurs, a positional deviation occurs between the centers 41C and 42C in the projected image 40P.

[0050] The premise for the reason for misalignment is that when exposing an arbitrary pattern onto a substrate through a photomask, if the exit angle (emission angle) of the light beams emitted from the photomask is perpendicular, the center position of the projected image of the pattern formed on the substrate when defocused is approximately the same as the center position of the projected image of the pattern formed on the substrate when focused. On the other hand, if the exit angle of the light beams emitted from the photomask is an angle other than perpendicular (90°±α: α is arbitrary), the center position of the projected image of the pattern formed on the substrate when defocused is different from the center position of the projected image formed on the substrate when focused. Furthermore, the exit angle corresponds to the angle of incidence of the light incident on the substrate.

[0051] By forming the measurement mark 40 described above and forming the regions A1 and B1, and the regions A2 and B2, the emission angle of the light beam emitted from the photomask can be set to an angle different from the vertical (90°±α: α is arbitrary). More specifically, the phase difference between the regions A1 and B1 of the measurement mark 40 and the phase difference between the regions A2 and B2 can make the emission angle different from the vertical.

[0052] Furthermore, in configuration 1 consisting of the vicinity of vertical side 411y and the vicinity of vertical side 421y, the arrangement of the marks near vertical side 411y and the vicinity of vertical side 421y is opposite, so the emission angles of the emitted light that has passed through areas A1 and B1, and areas A2 and B2 near vertical side 411y and the emitted light that has passed through areas A1 and B1, and areas A2 and B2 near vertical side 421y are opposite. As a result, when the pattern images of vertical sides 411y and 421y formed on the substrate are formed at a position higher in the Z-axis direction (opposite the direction of gravity) than the focus position (this is called positive defocus), the projected images of vertical sides 411y and 421y are closer to each other, and when the pattern of vertical sides 411y and 421y is formed at a position lower in the Z-axis direction than the focus position (this is called negative defocus), the projected images of vertical sides 412y and 421y are farther apart.

[0053] Furthermore, in configuration 2 configured near the vertical side 412y and near the vertical side 422y, the arrangement of the marks near the vertical side 412y and near the vertical side 422y is different from configuration 1. As a result, the pattern images of the vertical side 412y and the vertical side 422y formed on the substrate behave in the opposite manner to configuration 1. That is, when there is a positive defocus, the projected images of the vertical side 412y and the vertical side 422y formed on the substrate move apart, and when there is a negative defocus, the projected images of the vertical side 412y and the vertical side 422y move closer to each other.

[0054] Using the principles described above, a projected image 40P of the outer rectangle 41 and the inner rectangle 42 is obtained. The amount of positional deviation of the center 42C from the center 41C on the diagonal line L of the projected image 40P is defined as the "shift amount." A "positive" shift amount indicates positive defocus, and a "negative" shift amount indicates negative defocus. Figure 3(c) shows the relationship between the defocus amount and shift amount of the projected image 40P of the measurement mark 40. The solid line indicates a linear approximation, and the dotted line indicates a simulation value. This shows that the defocus amount and shift amount in the projected image 40P of the measurement mark 40 are strongly correlated and exhibit a linear relationship over a wide range. Therefore, by measuring the shift amount, it is possible to easily and accurately detect the defocus amount and adjust the focus from the measured shift amount. Specifically, when the centers 41C and 42C are aligned as shown in Figure 3(a), the shift amount is 0 (zero). 3(b), when the center 42C is shifted to the upper right direction with respect to the center 41C, the shift amount is "negative," indicating negative defocus. The shift amount may be calculated from the shortest distance between the centers 41C and 42C, or the shortest distance may be resolved into two components (X component and Y component) in two-dimensional directions (X direction and Y direction) of the substrate.

[0055] 17(a), the measurement mark may be a measurement mark 80 having a substantially cross-shaped pattern. The measurement mark 80 includes four substantially L-shaped portions constituting an outer cross (first mark) 81 and four substantially L-shaped portions constituting an inner cross (second mark) 82 concentric with the outer cross 81. Regions A1, B1, C, A2, and B2 are arranged adjacent to each other in this order near the outer cross 81 and the inner cross 82 along the X direction across the light-shielding film 30. For example, the X direction may be perpendicular to the linear portion of the measurement mark 80. As shown in FIGS. 17(b) and 17(c), projected images 81P and 82P of the outer cross 81 and the inner cross 82 projected through the projection optical system are shifted in opposite directions on the same straight line L80 within the projection plane depending on the defocus amount. Here, the amount of positional shift of the center 82C relative to the center 81C in the projected image 80P of the measurement mark 80 is defined as the "shift amount." The defocus amount and the shift amount also show a linear relationship in the projected image 80P, so that it is possible to measure the shift amount, detect the defocus amount from the shift amount, and perform focus adjustment.

[0056] Furthermore, the measurement mark 40 does not have to have only a box-in-box structure as shown in FIG. 1. For example, the outer structure may be a rectangle (the corners may not be connected) and the inner structure may be a cross. In FIG. 3, the position of the center 41C of the outer rectangle is used as a reference, and the position of the center 42C of the inner rectangle is used as a reference, and the distance between the two reference positions is measured to calculate the shift amount. Similarly, a reference position on the outer figure and a reference position on the inner figure can be determined, and the shift amount can be calculated by measuring the distance between the two reference positions. Therefore, the shapes of the outer and inner measurement marks 40 can be designed as appropriate.

[0057] [Method for detecting defocus amount and method for adjusting focus] A method for detecting the amount of defocus and a method for adjusting focus in a projection exposure apparatus using a phase shift mask 100 having measurement marks 40 will be described with reference to the flowchart shown in FIG.

[0058] First, an exposure apparatus 500 shown in FIG. 5 that performs defocus amount detection and focus adjustment will be described. The exposure apparatus 500 includes a light source LS, an illumination optical system 502, a projection optical system 504, a projection optical system controller 508, a mask stage 503 that holds a phase shift mask 100, a mask stage drive mechanism 507, a substrate stage 505 that holds a photosensitive substrate 515, which is an exposure target, and a substrate stage drive mechanism 506. The exposure apparatus 500 also includes a main controller 509 that controls the entire exposure apparatus 500, including the mask stage drive mechanism 507, the projection optical system controller 508, and the substrate stage drive mechanism 506. The projection optical system controller 508 controls drive elements corresponding to each lens element that constitutes the projection optical system 504, and can adjust the position and angle of each lens element. The mask stage drive mechanism 507 can move the mask stage 503 in a horizontal plane and in the optical axis direction of the projection optical system 504. The substrate stage drive mechanism 506 can move the substrate stage 505 in a horizontal plane and in the optical axis direction.

[0059] The mask stage driving mechanism 507 and the substrate stage driving mechanism 506 are also capable of adjusting the tilt of the mask stage 503 and the substrate stage 505, respectively. The mask stage driving mechanism 507 and / or the substrate stage driving mechanism 506 are capable of fine-tuning the distance in the optical axis direction between the phase shift mask 100 and the photosensitive substrate 515, i.e., focus adjustment. The projection optical system controller 508 is also capable of focus adjustment by fine-tuning the position and / or tilt of at least one of the lenses that make up the projection optical system 504. In this way, the mask stage driving mechanism 507, the projection optical system controller 508, and the substrate stage driving mechanism 506 constitute a focus adjustment mechanism in the exposure apparatus 500. The focus adjustment mechanism is controlled by the main controller 509.

[0060] A method for detecting the defocus amount in exposure apparatus 500 (steps S1 to S3 in FIG. 4) will be described. First, in exposure apparatus 500 shown in FIG. 5, phase shift mask 100 is placed on mask stage 503. Also, photosensitive substrate 515 coated with photoresist is placed on substrate stage 505.

[0061] Next, the measurement marks 40 of the phase shift mask 100 are projected onto a photosensitive substrate 515 for exposure (step S1 in FIG. 4). First, exposure light is emitted from a light source LS of the exposure apparatus 500. Examples of illumination light include deep ultraviolet (DUV, 302 nm, 313 nm, and 334 nm), i-line (365 nm), h-line (405 nm), and g-line (436 nm). The emitted exposure light enters an illumination optical system 502, where it is adjusted to a predetermined luminous flux, and is then irradiated onto the phase shift mask 100 held on a mask stage 503. The light that passes through the phase shift mask 100 carries the pattern of the measurement marks 40 drawn on the phase shift mask 100, and this pattern is irradiated via a projection optical system 504 onto a predetermined position on the surface (projection surface) of a photosensitive substrate 515 held on a substrate stage 505. As a result, the measurement marks 40 of the phase shift mask 100 are imaged and exposed onto the photosensitive substrate 515 at a predetermined magnification.

[0062] Next, the positional deviation (shift amount) of the center 42C from the center 41C is measured (see FIG. 3(b)) (step S2 in FIG. 4) in the projected image 40P of the measurement mark 40 exposed on the photosensitive substrate 515. The shift amount can be measured, for example, by observing the projected image 40P of the measurement mark 40 with an optical microscope.

[0063] Next, the defocus amount is calculated from the measured shift amount (step S3 in FIG. 4). As described above, the defocus amount and the shift amount show a linear relationship (see FIG. 3(c)), so the defocus amount can be easily and accurately calculated from the measured shift amount. Note that, regarding the relationship between the defocus amount and the shift amount as shown in FIG. 3(c), data may be obtained, for example, by performing a simulation, an experiment, or the like, prior to the detection of the defocus amount described above (steps S1 to S3 in FIG. 4).

[0064] Next, the focus adjustment method in the exposure apparatus 500 (steps S1 to S4 in FIG. 4) will be described. First, the defocus amount is detected using the method described above (steps S1 to S3 in FIG. 4). Next, based on the detected defocus amount, the focus adjustment mechanism (506, 507, 508) of the exposure apparatus 500 performs focus adjustment to correct (cancel) the defocus amount (step S4 in FIG. 4). Specifically, for example, the mask stage drive mechanism 507 and / or the substrate stage drive mechanism 506 may fine-tune the tilt and position in the optical axis direction of the mask stage 503 and / or the substrate stage 505, thereby fine-tuning the spacing in the optical axis direction between the phase shift mask 100 and the photosensitive substrate 515, thereby adjusting the focus. Additionally or alternatively, the projection optical system controller 508 may fine-tune the position and / or tilt of at least one of the lenses constituting the projection optical system 504, thereby adjusting the focus.

[0065] The detection of the defocus amount and focus adjustment described above may be performed prior to a photolithography process using an exposure apparatus, for example, in the manufacture of devices such as semiconductors and liquid crystal panels. That is, exposure may be performed using a projection optical system adjusted by the above-described focus adjustment method to manufacture devices. By using a projection optical system with adjusted focus, circuit pattern defects in the exposure process can be reduced, allowing devices to be manufactured efficiently.

[0066] [Variations] In the above embodiment, a defocus amount detection method and focus adjustment using one measurement mark 40 have been described, but this embodiment is not limited to this. For example, the phase shift mask 100 of this embodiment may be provided with only one measurement mark 40, or may be provided with multiple measurement marks 40. Furthermore, only one measurement mark 40 or multiple measurement marks 40 may be exposed onto the photosensitive substrate 515.

[0067] Although the above embodiment uses the projection exposure apparatus 500 shown in FIG. 5 , which is equipped with only one projection optical system, this embodiment is not limited to this. For example, a projection exposure apparatus equipped with multiple projection optical systems, such as that disclosed in Japanese Patent Application Laid-Open No. 2018-54847, a so-called multi-lens type exposure apparatus, can also use the phase shift mask 100 to similarly detect the defocus amount and adjust the focus. In this case, as described below, multiple measurement marks can be used to simultaneously detect the defocus amount and adjust the focus of each projection optical system. Note that multi-lens type exposure apparatuses are suitable for large-area exposure and are used, for example, to expose thin-film transistor (TFT) circuit patterns in the manufacture of flat panel displays (FPDs) such as liquid crystal displays (LCDs) and organic electroluminescent (EL) displays.

[0068] In this modified example, an example of a method for detecting a defocus amount and a method for adjusting a focus in a multi-lens exposure apparatus using a phase shift mask 200 provided with multiple measurement marks 40 as shown in FIG. 6(a) will be described. The multi-lens exposure apparatus used in this modified example has three projection optical systems PL1 to PL3. The multi-lens exposure apparatus used in this modified example is a scanning stepper (scanner). That is, the phase shift mask 200 and the photosensitive substrate are driven in the same direction (X direction) at the same speed relative to the projection optical systems PL1 to PL3, thereby exposing the measurement marks 40 formed on the phase shift mask 200 onto the photosensitive substrate. The other basic structure is the same as that of the exposure apparatus 500 shown in FIG. 5.

[0069] An example of a method for detecting the defocus amount (steps S1 to S3 in FIG. 4) will be described. First, phase shift mask 200 shown in FIG. 6(a) is placed in a multi-lens exposure tool. Phase shift mask 200 has a plurality of measurement marks 40 provided on substrate surface 10a of substrate 10. The structure is otherwise the same as phase shift mask 100 shown in FIG. 1. On substrate surface 10a of phase shift mask 200, three rows M1, M2, and M3, each consisting of a plurality of measurement marks 40 aligned in the X direction, are aligned in the Y direction perpendicular to the X direction. In addition, photosensitive substrate 215 is also set in the multi-lens exposure tool.

[0070] Next, the measurement marks 40 of the phase shift mask 200 are projected onto the photosensitive substrate 215 and exposed (step S1 in FIG. 4). First, in accordance with instructions from the control device of the multi-lens exposure apparatus, the mask stage and the substrate stage are synchronously driven in the X direction to perform scanning exposure on the first shot area 215A and the second shot area 215B on the photosensitive substrate 215. As a result, three rows of measurement mark images M1P, M2P, and M3P are formed on the substrate 215, as shown in FIG. 6(b). The rows M1P, M2P, and M3P are made up of images 40P of multiple measurement marks 40 lined up in the X direction. After the scanning exposure on the first shot area 215A and the second shot area 215B is completed, the control device moves (steps) the substrate stage 505 to positions corresponding to the third shot area 215C and the fourth shot area 215D. Then, scanning exposure is performed on the third shot area 215C and the fourth shot area 215D. As a result, three more measurement mark image rows M11P, M12P, and M13P are formed on the substrate 215. In this way, the photosensitive substrate 215 is exposed to the projected images 41P of the multiple measurement marks 40. Note that the measurement mark image rows M1P and M11P are formed by the projection optical system PL1, the measurement mark image rows M2P and M12P are formed by the projection optical system PL2, and the measurement mark image rows M3P and M13P are formed by the projection optical system PL3.

[0071] Next, the shift amount of the projected image 40P of the measurement mark 40 exposed on the photosensitive substrate 215 is detected (step S2 in FIG. 4), and the defocus amount is calculated based on the detected shift amount (step S3 in FIG. 4). In this modification, the defocus amount can be detected for each projected image of the multiple marks 40 formed on the photosensitive substrate 215. FIG. 6(c) shows the relationship between the position (position in the X direction) of the projected image 40P on the photosensitive substrate 215 and the defocus amount (position in the Z direction) at that position for three measurement mark image rows M1P, M2P, and M3P, with the graph centered at the intersection of the center of the X axis and the center of the Y axis of the photosensitive substrate 215. In this way, in this modification, the defocus amount across the entire surface of the photosensitive substrate 215 can be detected simultaneously. Note that the phase shift mask 200 may have one or more measurement marks 40 and patterns for manufacturing devices.

[0072] Next, an example of a focus adjustment method (steps S1 to S4 in FIG. 4) will be described. First, the defocus amount in the multi-lens exposure apparatus is detected over the entire surface of the photosensitive substrate 215 using the method described above (steps S1 to S3 in FIG. 4). Next, focus adjustment is performed for each projection optical system based on the detected defocus amount (step S4 in FIG. 4). As with the projection exposure apparatus 500, focus adjustment is performed by the focus adjustment mechanism of each projection optical system based on the detected defocus amount so as to independently correct (cancel) the defocus amount (step S4 in FIG. 4).

[0073] In this modification, the defocus amount can be detected simultaneously over the entire surface of the photosensitive substrate 215, allowing for efficient focus adjustment. FIG. 6(d) shows the detection results obtained by performing the same defocus amount detection (steps S1 to S3 in FIG. 4) again after focus adjustment. From FIGS. 6(c) and (d), it can be seen that the defocus amount of the photosensitive substrate 215 is 2 15It can be seen that the focus is optimized over a wide range of the surface.

[0074] The defocus amount detection method and focus adjustment method of this modified example enable efficient defocus amount detection and focus adjustment over a wide range on the surface of the photosensitive substrate 215. Therefore, the defocus amount detection method and focus adjustment method of this modified example are suitable for use in the manufacture of FPDs, which involve large-area exposure. In FPD manufacture, if defocus occurs in the exposure of a TFT circuit pattern, it can cause linewidth errors that affect the electrical characteristics of the TFT circuit pattern, potentially degrading the quality of the finished display. The defocus amount detection method and focus adjustment method of this modified example can easily and accurately optimize focus over the entire photosensitive substrate, thereby preventing such degradation in the quality of the finished display.

[0075] A resolution chart 45 can also be provided together with the measurement marks 40. By providing the resolution chart 45, it is possible to check the line width that can be exposed by the projection exposure apparatus. The resolution chart 45 may have only one line width, or may have two or more different line widths. The resolution chart may also be arranged over the entire substrate, similar to the measurement marks 40 in FIG. 6. This allows the projection exposure apparatus to check the line width that can be exposed at each position over the entire substrate.

[0076] In the above embodiment and modified examples, the phase shift mask 100 for defocus inspection on which the measurement marks 40 are formed has been described as an example. However, the mask may also have other patterns formed thereon, such as a circuit pattern (device pattern) for exposing a photosensitive substrate or an alignment mark required for alignment. In this case, the phase shift film 20 may form both a detection mark and a device pattern. Furthermore, the phase shift film 20 may also be used for a phase shift mask having a device pattern but no detection mark 40. In this case, the phase shift film 20 may form a device pattern. [Example]

[0077] The phase shift mask (detection element), the defocus amount detection method, and the focus adjustment method will be specifically described below using examples and comparative examples, but the present invention is not limited to these examples and comparative examples.

[0078] Formation of phase shift film [Phase shift film PS1] The phase shift film PS1 was formed by reactive sputtering. First, a circular parallel plate made of quartz glass was prepared as the substrate 10 (size: 3 inches in diameter, 0.5 mm thick). Using a DC magnetron sputtering system, a ZrSi alloy target was used as the sputtering target. While introducing an Ar-N2 mixed gas, reactive sputtering was performed using a capacitively coupled magnetron direct current plasma method to form a 100 nm thick phase shift film PS1. The composition (atomic ratio) of the ZrSi alloy target was Zr:Si = 1:2. The deposition conditions were a mixed gas total pressure of 0.3 Pa, an Ar flow rate of 47.5 sccm, an N2 flow rate of 2.5 sccm, and a DC power of 1.5 kW.

[0079] [Phase shift film PS2~PS5] Phase shift films PS2 to PS5 were formed on substrate 10 in the same manner as for phase shift film PS1, except that the ratio of the Ar flow rate to the N2 flow rate in the Ar-N2 mixed gas was changed as shown in FIG.

[0080] [Phase shift film PS11] A phase shift film PS11 was formed on the substrate 10 in the same manner as for the phase shift film PS1, except that an Ar-N2-O2 mixed gas was used instead of the Ar-N2 mixed gas. The film formation conditions were a mixed gas total pressure of 0.3 Pa, an Ar flow rate of 30 sccm, an N2 flow rate of 19 sccm, an O2 flow rate of 1 sccm, and a DC output of 1.5 kW.

[0081] [Phase shift film PS12~PS14] Phase shift films PS12 to PS14 were formed on substrate 10 in the same manner as phase shift film PS11, except that the ratios of the Ar flow rate, N2 flow rate, and O2 flow rate of the mixed gas were changed as shown in FIG.

[0082] Evaluation of physical properties of phase shift films (1) Composition analysis The phase shift films PS1 to PS5 and PS11 to PS14 were subjected to composition analysis by X-ray photoelectron spectroscopy (XPS). The results are shown in FIG. 7. XPS was performed using Ar + The surface of each phase shift film was dug by about 10 nm by ion sputtering, and then the measurement was carried out.

[0083] (2) Simulation of refractive index, attenuation coefficient, film thickness and element transmittance The refractive indexes and extinction coefficients of the phase shift films PS1 to PS5 and PS11 to PS14 were measured by ellipsometry at six wavelengths (DUV (wavelengths 302 nm, 313 nm, and 334 nm), i-line (365 nm), h-line (405 nm), and g-line (436 nm)). From the refractive index measurements, the film thicknesses of the phase shift films PS1 to PS5 and PS11 to PS14 that would provide a 90-degree phase shift at each of the six wavelengths were calculated. Furthermore, the transmittance (device transmittance) of the devices (substrate and phase shift film) on which the phase shift films PS1 to PS5 and PS11 to PS14 were formed at the calculated film thicknesses was calculated by simulation. The simulation was performed using the simulation software "TFCalc." Based on the refractive index and extinction coefficient measurements at each of the six wavelengths obtained by ellipsometry, the transmittance of the phase shift films PS1 to PS5 and PS11 to PS14 at each film thickness that would provide a 90-degree phase shift at each wavelength was calculated. Here, the transmittance refers to the external transmittance (device transmittance) that also takes reflection into consideration. The measured refractive index and attenuation coefficient, as well as the calculated film thickness and device transmittance, are shown in Figures 8 to 13.

[0084] Fabrication of phase shift mask blanks 150 To simulate measurement mark 40 of a box-in-box pattern provided on phase shift mask 100 shown in Figure 1, two types of phase shift mask blanks 150a and 150b were fabricated and the physical properties of phase shift film 20 were obtained. Phase shift mask blank 150a used the phase shift film PS4 described above. Phase shift mask blank 150b used the phase shift film PS13 described above.

[0085] <Fabrication of Phase Shift Mask Blank 150a> First, a square parallel plate made of quartz glass was prepared as substrate 10 (size: 6 inches on a side, 0.25 inches thick). Phase shift film PS4 having the composition shown in FIG. 7 was formed on substrate 10 as phase shift film 20 by the reactive sputtering described above. The thickness of phase shift film PS4 was set to 51.6 nm, which corresponds to a phase shift of 90° for light with a wavelength of 365 nm as shown in FIG. 11 (FIG. 14(a)).

[0086] <Fabrication of Phase Shift Mask Blank 150b> A phase shift mask 150b was fabricated in the same manner as the phase mask blank 150a, except that a phase shift film PS13 was formed on the substrate 10 instead of the phase shift film PS4. The film thickness was set to 120.7 nm, which gives a phase shift of 90° for light with a wavelength of 365 nm as shown in FIG.

[0087] <Design of Phase Shift Masks 100A and 100B> Phase shift masks 100A and 100B were designed on the fabricated phase shift mask blanks 150a and 150b, with measurement marks 40 of the box-in-box pattern shown in Fig. 1. The sizes (design values) of measurement marks 40 formed on phase shift masks 100A and 100B are as follows: Width in the X direction and width in the Y direction of the outer rectangle 41: X: 90 μm, Y: 90 μm Width in the X direction and width in the Y direction of the inner rectangle 42: X: 46 μm, Y: 46 μm Width (Wc) of horizontal sides 411x, 412x, 421x, 422x and vertical sides 411y, 412y, 421y, 422y: 8 μm Width of area A1 (Wa1): 16 μm Width of area A2 (Wa2): 1 μm Width of region B1 (Wb1): 1 μm Width (Wb2) of the region B2 between the outer rectangle 41 and the inner rectangle 42: 16 μm Here, the width of the outer rectangle 41 in the X direction is the length from one end to the other end of the outer rectangle 41 in the X direction, and the width in the Y direction is the length from one end to the other end of the outer rectangle 41 in the Y direction. Similarly, the width of the inner rectangle 42 in the X direction is the length from one end to the other end of the inner rectangle 42 in the X direction, and the width in the Y direction is the length from one end to the other end of the inner rectangle 42 in the Y direction.

[0088] <Simulation of the relationship between shift amount and defocus amount> Using the refractive index, attenuation coefficient, film thickness, and element transmittance measured from the manufactured phase shift mask blank 150a and the design values ​​of the measurement marks, phase shift mask 100A was placed in a projection exposure tool, and the relationship between the shift amount and the defocus amount was simulated for projected image 40P (see Figures 3(a) and (b)) projected through a projection optical system with light of a wavelength of 365 nm. The results are shown in Figure 16. Similarly, the relationship between the shift amount and the defocus amount was simulated for phase shift mask 100B. The results are also shown in Figure 16.

[0089] As shown in FIG. 16, the shift amount and defocus amount for the measurement marks 40 of the phase shift masks 100A and 100B exhibit a linear relationship over a wide range. In the region where the shift amount and defocus amount exhibit a linear relationship, for example, the shift amount of the measurement marks 40 can be measured using an optical microscope, and the defocus amount can be easily and accurately calculated based on the measurement results. Then, focus adjustment can be easily performed in the projection exposure apparatus to correct (cancel) this defocus amount. In this way, the phase shift masks 100A and 100B function as detection elements for detecting the defocus amount of light passing through the projection optical system.

[0090] FIG. 16 compares the simulation results for phase shift masks 100A and 100B. Compared with phase shift mask 100A employing phase shift film PS4, phase shift mask 100B employing phase shift film PS13 exhibits a linear relationship between shift amount and defocus amount over a wider range. Therefore, shift mask 100B can detect larger defocus amounts. While phase shift mask 100A can detect defocus amounts in the range of −30 μm to +15 μm, phase shift mask 100B can detect defocus amounts in the wider range of −30 μm to +25 μm. One possible reason for this is presumably that, as shown in FIG. 11, the element transmittance (94.08%) of phase shift film PS13 employed in phase shift mask 100B for 365 nm light is higher than the element transmittance (56.94%) of phase shift film PS4 employed in phase shift mask 100A. The element transmittance corresponds to the transmittance in regions A1 and A2 of phase shift masks 100A and 100B. The element transmittance of phase shift film PS13 (94.08%) is higher than that of phase shift film PS4 (56.94%) because the atomic ratio of oxygen (O) to zirconium (Zr) (O / Zr) is higher in phase shift film PS13 than in phase shift film PS4. As the atomic ratio (O / Zr) increases, the band gap of the film material increases and the attenuation coefficient decreases. This results in higher transmittance.

[0091] As shown in FIG. 7, oxygen gas is not introduced into the phase shift films PS1 to PS5 during deposition. Therefore, the atomic ratio (O / Zr) of oxygen (O) to zirconium (Zr) in the phase shift films PS1 to PS5 is less than 0.1. The oxygen contained in the phase shift films PS1 to PS5 is not intentionally introduced, but is oxygen taken in from the air by oxidation. On the other hand, oxygen gas is actively introduced into the phase shift films PS11 to PS14 during deposition. Therefore, the atomic ratio (O / Zr) of oxygen (O) to zirconium (Zr) in the phase shift films PS11 to PS14 is 0.1 or greater.

[0092] The physical properties of phase shift films PS1 to PS5 and PS11 to PS14 for 365 nm light (i-line) are compared in Figure 11. Phase shift films PS11 to PS14 with an atomic ratio (O / Zr) of 0.1 or greater have higher element transmittance than phase shift films PS1 to PS5 with an atomic ratio (O / Zr) of less than 0.1. Phase shift films PS11 to PS14 with an atomic ratio (O / Zr) of 0.1 or greater exhibit sufficiently high transmittance for 365 nm light (i-line). From these results, it is inferred that phase shift mask 100 using phase shift films PS11 to PS14 with an atomic ratio (O / Zr) of 0.1 or greater is excellent as a detection element for the defocus amount of a projection optical system when using 365 nm light (i-line). In the phase shift films PS11 to PS14, the atomic ratio (Si / Zr) was 0.8 to 1.2, the atomic ratio (N / Zr) was 0.04 to 2.3, and the atomic ratio (O / Zr) was 0.1 to 3.4.

[0093] Furthermore, even among the phase shift films PS1 to PS5 with an atomic ratio (O / Zr) of less than 0.1, for example, phase shift films PS3 to PS5 with an atomic ratio (Si / Zr) of 1.00 to 1.20 and an atomic ratio (N / Zr) of 2.1 to 2.6 have higher element transmittance than phase shift films PS1 and PS2 with atomic ratios (Si / Zr) and (N / Zr) outside the above ranges. From these results, it is inferred that phase shift mask 100 using phase shift films PS3 to PS5 with an atomic ratio (Si / Zr) of 1.00 to 1.20 and an atomic ratio (N / Zr) of 2.1 to 2.6 can be fully used as a detection element for the defocus amount of a projection optical system when using 365 nm light (i-line).

[0094] 8 to 10 and 12 to 13, the phase shift films PS1 to PS5 and PS11 to PS14 exhibit the same tendency as the element transmittance for 365 nm light shown in Fig. 11. Therefore, it is presumed that the phase shift films PS3 to PS5 and PS11 to PS14 are fully usable as elements for detecting the defocus amount of a projection optical system when using light with wavelengths of 302 nm (DUV, Fig. 8), 313 nm (DUV, Fig. 9), 334 nm (DUV, Fig. 10), 405 nm (h-line, Fig. 12), and 436 nm (g-line, Fig. 13).

[0095] The phase shift films PS3 to PS5 and PS11 to PS14 used in this example can be used for a phase shift mask having both a detection mark and a device pattern, in which case both the detection mark and the device pattern may be formed.Furthermore, the phase shift films PS3 to PS5 and PS11 to PS14 can be used for a phase shift mask having a device pattern but no detection mark, in which case the device pattern may be formed. [Industrial Applicability]

[0096] The phase shift mask 100 of this embodiment can be used as a detection element for the defocus amount of a projection optical system. The phase shift mask 100 of this embodiment can be used not only in an exposure apparatus but also as a detection element for the defocus amount of an optical measuring instrument, a laser processing machine, etc. [Explanation of symbols]

[0097] 10 Base material 20 Phase shift film 30 Light-shielding film 40 Measurement Mark 100,200 Phase Shift Mask 500 exposure equipment LS light source 502 Illumination optical system 504 Projection optical system 508 Projection Optical System Controller 503 Mask Stage 507 Mask stage drive mechanism 505 Substrate Stage 506 Substrate stage driving mechanism 509 Main Controller A1: Area on the substrate surface (first area) A2 Base material surface area (4th area) B1: Substrate surface area (second area) B2 Base material surface area (5th area) C. Substrate surface region (third region)

Claims

1. A substrate; a first semi-transparent layer and a second semi-transparent layer; a light-shielding layer; On the surface of the substrate, along an arrangement direction parallel to the surface, a first region in which a first semi-transparent layer is disposed; a second region in which the surface of the substrate is exposed; a third region in which the light-shielding layer is disposed; and a fourth region in which the second semi-transparent layer is disposed; and a fifth region in which the surface of the substrate is exposed, and a measurement mark having a pattern provided adjacent to the fifth region is formed; when light of a predetermined wavelength is irradiated onto the measurement mark, a phase difference between a first light transmitted through the first region and the fourth region and a second light transmitted through the second region and the fifth region is 90°±50°, the first semi-transparent layer and the second semi-transparent layer contain zirconium (Zr) and silicon (Si); A detection element, wherein the first semi-transparent layer and the second semi-transparent layer have a transmittance of 40% or more for light with a wavelength of 250 nm to 440 nm.

2. the measurement mark has a first portion in which the first pattern, the second pattern, the third pattern, and the fourth pattern are arranged in this order along the first arrangement direction, In the first pattern and the fourth pattern, a first region, a second region, a third region, a fourth region, and a fifth region are arranged in this order from one side to the other side in the first arrangement direction, 2. The detection element of claim 1, wherein in the second pattern and the third pattern, a first region, a second region, a third region, a fourth region, and a fifth region are arranged in this order from the other side to one side of the first arrangement direction.

3. the measurement mark has a second portion in which the fifth pattern, the sixth pattern, the seventh pattern, and the eighth pattern are arranged in this order along a second arrangement direction different from the first arrangement direction, and In the fifth pattern and the eighth pattern, a first region, a second region, a third region, a fourth region, and a fifth region are arranged in this order from one side to the other side in the second arrangement direction, 3. The detection element of claim 2, wherein in the sixth pattern and the seventh pattern, a first region, a second region, a third region, a fourth region, and a fifth region are arranged in this order from the other side to one side of the second array direction.

4. The sensing element of claim 3 , wherein the measurement mark has the first portion and the second portion.

5. The detection element according to claim 1 , wherein the width of the second region and the width of the fourth region are smaller than the width of the third region in the arrangement direction.

6. the measurement mark has a first mark formed by the pattern and a second mark formed by the pattern, The detection element of claim 1 , wherein the first mark is larger than the second mark.

7. The detection element according to claim 6 , wherein the first mark or the second mark is substantially rectangular.

8. The detection element according to claim 6 , wherein the first mark or the second mark is substantially cross-shaped.

9. The detection element according to claim 1 , wherein the phase difference between the first light and the second light is 90°±20°.

10. The detection element according to claim 9 , wherein the phase difference between the first light and the second light is 90°±5°.

11. The detection element of claim 1 , wherein the first semi-transparent layer and the second semi-transparent layer contain zirconium (Zr), silicon (Si), and nitrogen (N).

12. The detection element according to claim 11 , wherein the first semi-transparent layer and the second semi-transparent layer further contain oxygen (O).

13. 13. The detection element according to claim 12, wherein the atomic ratio of oxygen to zirconium (O / Zr) in the first semi-transparent layer and the second semi-transparent layer is 0.1 or more.

14. In the first semi-transparent layer and the second semi-transparent layer, an atomic ratio of the silicon to the zirconium (Si / Zr) of 0.8 to 1.2; the atomic ratio of the nitrogen to the zirconium (N / Zr) is 0.04 to 2.3; 14. The detection element according to claim 13, wherein an atomic ratio of said oxygen to said zirconium (O / Zr) is 0.1 to 3.

4.

15. In the first semi-transparent layer and the second semi-transparent layer, an atomic ratio of the silicon to the zirconium (Si / Zr) of 1.00 to 1.20; 12. The detection element according to claim 11, wherein the atomic ratio of nitrogen to zirconium (N / Zr) is 2.1 to 2.

6.

16. In the first semi-transparent layer and the second semi-transparent layer, 16. The sensing element of claim 15, wherein the atomic ratio of oxygen to zirconium (O / Zr) is less than 0.

1.

17. 2. The detection element according to claim 1, wherein the refractive index of the first semi-transparent layer and the second semi-transparent layer for light with a wavelength of 365 nm is 1.7 to 3.

0.

18. 2. The detection element according to claim 1, wherein the first semi-transparent layer and the second semi-transparent layer have an attenuation coefficient of 0.2 or less for light with a wavelength of 365 nm.

19. A phase shift mask comprising the detection element according to claim 1.

20. 20. The phase shift mask of claim 19, wherein the phase shift mask comprises a resolution chart.

21. 20. The phase shift mask of claim 19, comprising a plurality of said measurement marks.

22. the second semi-transparent layer is formed continuously over a third region and a fourth region on the surface of the substrate, 20. The phase shift mask according to claim 19, wherein in the third region, the light-shielding layer is disposed on the second semi-transmitting layer.

23. 20. A method for detecting a defocus amount of a projection optical system using the phase shift mask according to claim 19, comprising: irradiating the phase shift mask with light of a predetermined wavelength to form a projected image of the measurement mark on a projection surface by the projection optical system; measuring a positional deviation amount of the projected image of the measurement mark from a predetermined position on the projection plane; a defocus amount detecting method including calculating the defocus amount from the measured positional deviation amount;

24. 24. The method for detecting a defocus amount according to claim 23, further comprising the steps of: placing a photosensitive substrate on the projection plane; and exposing the photosensitive substrate to the pattern of the measurement marks.

25. Detecting the defocus amount of the projection optical system by the defocus amount detection method according to claim 23; A focus adjustment method for a projection optical system, comprising adjusting the focus of the projection optical system based on the detected defocus amount.

26. 26. A device manufacturing method, comprising: exposing a photosensitive substrate with a predetermined pattern using the projection optical system adjusted by the focus adjustment method according to claim 25.

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