CN116830035A

CN116830035A - Phase shift mask, detection element, defocus amount detection method, focus adjustment method, and device manufacturing method

Info

Publication number: CN116830035A
Application number: CN202280014132.2A
Authority: CN
Inventors: 泷优介; 矢岛海都; 牛田正男; 冨冈贞祐; 原笃史; 铃木一弘; 樋口潔
Original assignee: Nikon Corp
Current assignee: Nikon Corp
Priority date: 2021-04-30
Filing date: 2022-04-22
Publication date: 2023-09-29
Also published as: TW202246884A; KR20240000446A; JPWO2022230772A1; WO2022230772A1

Abstract

The present invention relates to a phase shift mask (100, 200) comprising a substrate (10), a1 st semi-transparent layer (20), a2 nd semi-transparent layer (20), and a light shielding layer (30), wherein a measurement mark is formed on the surface of the substrate, the measurement mark having a pattern in which the following regions are provided adjacently along an arrangement direction parallel to the surface: a1 st region (A1) provided with A1 st semi-permeable layer; a2 nd region (B1) exposed on the surface of the substrate; a 3 rd region (C) in which the light shielding layer is disposed; a 4 th region (A2) provided with A2 nd semi-permeable layer; and a 5 th region (B2) where the surface of the base material is exposed.

Description

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

Technical Field

The 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

In a photolithography process, which is one of the processes for manufacturing devices such as a semiconductor device, a liquid crystal display device, an image pickup device (such as a CCD), and a thin film magnetic head, a projection exposure apparatus is used to transfer-expose a pattern of a reticle as a mask onto a wafer or a glass plate (hereinafter referred to as a photosensitive substrate) coated with a photoresist through a projection optical system. In the manufacture of devices, it is important to perform exposure without blurring of a pattern or color unevenness due to defocusing.

As a means for evaluating focusing performance in a projection exposure apparatus, PSFM (phase shift focus monitor ) is known (for example, patent literature 1). In the evaluation method described in patent document 1, exposure is first performed using a phase shift mask on which a measurement mark is formed. The following phenomena occur at this time: the image of the pattern formed when exposure is performed in a defocused state is shifted (shifted) in position in the lateral direction (in the direction in the plane perpendicular to the optical axis of the projection optical system) with respect to the image of the pattern formed when exposure is performed in a focused state. By utilizing this phenomenon, the position shift amount is converted into a defocus amount, and the focusing performance is evaluated.

Prior art literature

Patent literature

Patent document 1: U.S. Pat. No. 5300786 Specification

Disclosure of Invention

According to the 1 st aspect, there is provided a phase shift mask comprising a substrate, 1 st and 2 nd semi-transmissive layers (1 st and 2 nd phase shift films), and a light shielding layer (light shielding film), wherein a measurement mark having a pattern in which the following regions are provided adjacently along an arrangement direction parallel to the surface is formed on the surface of the substrate: a 1 st region provided with a 1 st semi-transmissive layer (1 st phase shift film); a 2 nd region exposed from the surface of the base material; a 3 rd region in which the light shielding layer (light shielding film) is disposed; a 4 th region provided with a 2 nd semi-transmissive layer (2 nd phase shift film); and a 5 th region exposed from the surface of the base material.

According to the 2 nd aspect, there is provided a detection element for detecting a defocus amount of light of a predetermined wavelength transmitted through a projection optical system, the detection element including: a substrate; 1 st and 2 nd semi-permeable layers (1 st and 2 nd phase shift films); and a light shielding layer (light shielding film) on the surface of the substrate, wherein the measurement mark has a pattern in which the following regions are adjacently arranged along an arrangement direction parallel to the surface: a 1 st region provided with a 1 st semi-transmissive layer (1 st phase shift film); a 2 nd region exposed from the surface of the base material; a 3 rd region in which the light shielding layer (light shielding film) is disposed; a 4 th region provided with a 2 nd semi-transmissive layer (2 nd phase shift film); and a 5 th region exposed from the surface of the base material.

According to the 3 rd aspect, there is provided a method of detecting a defocus amount of a projection optical system using the phase shift mask of the 1 st aspect or the detection element of the 2 nd aspect, comprising: irradiating the phase shift mask or the detection element with light having a predetermined wavelength, and forming a projection image of the measurement mark on a projection surface based on the projection optical system; measuring a positional deviation of a projection image of the measurement mark from a predetermined position on the projection surface; and calculating the defocus amount based on the measured positional deviation.

According to the 4 th aspect, there is provided a focus adjustment method of a projection optical system, comprising: detecting a defocus amount of the projection optical system by the defocus amount detection method of claim 3; and adjusting a focus of the projection optical system based on the detected defocus amount.

According to the 5 th aspect, there is provided a method for manufacturing a device, comprising exposing a photosensitive substrate in a predetermined pattern using the projection optical system adjusted by the focus adjustment method of the 4 th aspect.

Drawings

Fig. 1 (a) is a schematic view of the lower surface of a phase shift mask having a measurement mark (a view seen from a surface on which the measurement mark is formed) according to the embodiment, and fig. 1 (b) is a schematic view of a section of IB-IB line of fig. 1 (a).

Fig. 2 (a) is an enlarged view of the region IIA of fig. 1 (a), and fig. 2 (b) is a schematic view of a section of the IIB-IIB line of fig. 2 (a).

Fig. 3 (a) is a diagram showing a projection image of a measurement mark (a pattern of a box in box) in an embodiment of a state in which a focus is in focus (defocus amount is 0 (zero)), and fig. 3 (b) is a diagram showing a projection image of a measurement mark in a state in which a focus is out of focus (defocus amount is not 0 (zero)). Fig. 3 (c) is a diagram showing a relationship between the defocus amount and the offset amount in the embodiment.

Fig. 4 is a flowchart showing a defocus amount detection method and a focus adjustment method of the embodiment.

Fig. 5 is a schematic diagram of an exposure apparatus that performs defocus amount detection and focus adjustment of the embodiment.

Fig. 6 (a) is a schematic view of a phase shift mask provided with a plurality of measurement marks in a modification example, and fig. 6 (b) is a schematic view of a photosensitive substrate to which a plurality of measurement marks are exposed. Fig. 6 (c) is a diagram showing the defocus amount on the photosensitive substrate before focus adjustment in the modification example, and fig. 6 (d) is a diagram showing the defocus amount on the photosensitive substrate after focus adjustment.

Fig. 7 is a table showing the gas flow rates and composition ratios at the time of film formation of the phase shift films PS1 to PS 14.

FIG. 8 is a table showing the film thicknesses of the phase shift films PS1 to PS14 and the optical characteristics with respect to light having a wavelength of 302 nm.

FIG. 9 is a table showing the film thicknesses of the phase shift films PS1 to PS14 and the optical characteristics with respect to light having a wavelength of 313 nm.

FIG. 10 is a table showing the film thicknesses of the phase shift films PS1 to PS14 and the optical characteristics with respect to light having a wavelength of 334 nm.

FIG. 11 is a table showing the film thicknesses of the phase shift films PS1 to PS14 and the optical characteristics with respect to light having a wavelength of 365 nm.

FIG. 12 is a table showing the film thicknesses of the phase shift films PS1 to PS14 and the optical characteristics with respect to light having a wavelength of 405 nm.

FIG. 13 is a table showing the film thicknesses of the phase shift films PS1 to PS14 and the optical characteristics with respect to light having a wavelength of 436 nm.

Fig. 14 (a) to (f) are diagrams for explaining a method of manufacturing a phase shift mask having a measurement mark in the embodiment.

Fig. 15 (a) to (f) are diagrams for explaining a method of manufacturing a phase shift mask having a measurement mark in the embodiment.

Fig. 16 is a simulation result of the relationship between the offset amount and the defocus amount performed in the embodiment.

Fig. 17 (a) is a diagram showing a measurement mark of a cross pattern, fig. 17 (b) is a diagram showing a projection image of the measurement mark in a state where the focus is in focus (defocus amount is 0 (zero)), and fig. 17 (c) is a diagram showing a projection image of the measurement mark in a state where the focus is out of focus (defocus amount is not 0 (zero)).

Fig. 18 is a phase shift mask with measurement marks without a phase shift film.

Detailed Description

[ phase shift mask ]

A phase shift mask 100 with measurement marks 40 shown in fig. 1 is illustrated. The phase shift mask 100 is used as a detection element for detecting a defocus amount of light (exposure light) of a predetermined wavelength transmitted through a projection optical system mounted in a projection exposure apparatus, for example. The phase shift mask 100 includes 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-transmissive film/semi-transmissive layer) 20 formed on the substrate surface 10 a. The phase shift film 20 is formed in the vicinity of the light shielding film 30. The light shielding film 30 constitutes the measurement mark 40. In the present embodiment, as the measurement marks 40, a so-called box-in-box pattern composed of pairs of concentric squares (or rectangles) is used. The details of the measurement marks 40 used in the present embodiment are described below.

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, the region A1, the region B1, the region C, the region A2, and the region B2 are arranged in this order on the substrate surface 10a along the X direction intersecting the phase shift film 20 and the light shielding film 30. The phase shift film 20 is disposed in the regions A1 and A2. The phase shift film 20 is not present in the regions B1 and B2, and the substrate surface 10a is exposed. A light shielding film 30 is disposed in the region C. The measurement mark 40 includes at least a region C, and may include a region A1, a region A2, a region B1, and a region B2 in addition to the region C. When light of a predetermined wavelength (exposure light) is irradiated to the phase shift mask, the phases of the light (1 st light) transmitted through the regions A1 and A2 are the same, and the phases of the light (2 nd light) transmitted through the regions B1 and B2 are the same. On the other hand, since the phase shift film 20 is formed, the phase of the light transmitted through the regions A1 and A2 is shifted, unlike the phase of the light transmitted through the regions B1 and B2. The regions A1, B1, C, A2, and B2 of the present embodiment correspond to the "1 st region", "2 nd region", "3 rd region", "4 th region", and "5 th region" of the present invention, respectively. The "X direction" of the present embodiment corresponds to the "arrangement direction" of the present invention. The phase shift film 20 disposed in the region A1 corresponds to the "1 st phase shift film", "1 st semi-permeable layer", or "1 st semi-permeable film", and the phase shift film 20 disposed in the region A2 corresponds to the "2 nd phase shift film", "2 nd semi-permeable layer", or "2 nd semi-permeable film". The basic arrangement (regions A1, B1, C, A, B2) of the phase shift film 20 and the light shielding film 30 of the present embodiment corresponds to the "pattern" of the present invention.

When the phase change substance is disposed on the measurement mark, the projection image of the measurement mark on the projection surface via the projection optical system is shifted in position in the projection surface orthogonal to the optical axis of the projection optical system according to the defocus amount thereof. As described above, the phase shift mask 100 of the present embodiment adopts the basic arrangement (the regions A1, B1, C, A, and B2) unique to the light shielding film 30 and the phase shift film 20 forming the measurement mark 40. According to this specific basic configuration, the correlation between the defocus amount of the projection image of the measurement mark 40 and the positional shift amount on the projection surface is enhanced, and the defocus amount can be easily and accurately detected using the phase shift mask 100. As a result, the focus adjustment is easy. The reason for this is presumed that the interference between the light transmitted through the region A1 and the light transmitted through the region B1, which is generated on one side of the region C where the mark is formed, is correlated with the interference between the light transmitted through the region A2 and the light transmitted through the region B2, which is generated on the other side of the region C.

When light (exposure light) of a predetermined wavelength is irradiated to the phase shift mask, the phase difference between the 1 st light transmitted through the areas A1 and A2 where the phase shift film is arranged and the 2 nd light transmitted through the areas B1 and B2 where the substrate surface 10a is exposed is 90 ° ± 50 °, preferably 90 ° ± 20 °, more preferably 90 ° ± 5 °, and still more preferably 90 ° ± 3 °. If the phase difference is within the above range, it is easier to detect the defocus amount and adjust the focus 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 according to the wavelength of the light (exposure light) transmitted through the phase shift mask 100. That is, the phase shift film 20 is preferably configured such that the phase difference falls within the above range.

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 > Wa2 >). The ratio of the width Wb1 to the width Wc (Wb 1/Wc) is preferably 0.1 to 0.2, more preferably 0.1 to 0.15, and still more preferably 0.1 to 0.13. The ratio of the width Wa2 to the width Wc (Wa 2/Wc) is preferably 0.1 to 0.2, more preferably 0.1 to 0.15, and still more preferably 0.1 to 0.13. The width Wb1 and the width Wa2 may be substantially the same (Wb 1=wa2). The width Wb1 and the width Wa2 may be smaller than the width Wa1 of the area A1. Further, the width Wa1 is preferably 2 times or more the width Wc. By having the above-described relationship among the width Wa1, the width Wb1, the width Wc, and the width Wa2, it is easier to detect the defocus amount and adjust the focus.

The width Wa1, the width Wb1, the width Wc, the width Wa2 can be appropriately designed in consideration of the wavelength of exposure light and the like of the projection exposure apparatus using the phase shift mask 100.

The measurement mark 40 of the present embodiment is not limited in shape as long as it includes a portion where straight lines oppose each other. The measurement mark 40 (light shielding film 30) includes a straight line portion, and the X direction intersecting the pattern formed by the light shielding film 30 may be a direction orthogonal to the extending direction of the straight line portion. In this case, the width of each region is a width (length) in a direction orthogonal to the extending direction of the straight line portion.

The material of the substrate 10 is not particularly limited as long as the exposure light can sufficiently pass through the projection exposure apparatus using the phase shift mask 100. For example, quartz glass may be used. The thickness of the substrate 10 may be, for example, 5mm to 30mm, or 7mm to 20mm.

The material of the light shielding film 30 is not particularly limited as long as the exposure light of the projection exposure apparatus using the phase shift mask 100 can be sufficiently shielded. For example, a metal such as chromium may be used. Specifically, chromium oxide (CrO) and chromium nitride (CrN) may be mentioned. The thickness of the light shielding film 30 is, for example, 50nm to 300nm, preferably 80nm as a lower limit, more preferably 100nm as a lower limit, 200nm as an upper limit, and more preferably 150nm as an upper limit. In addition, as shown in fig. 2 (b), a phase shift film 20 may be present under the light shielding film 30. In the present embodiment, the phase shift film 20 is continuously formed over the region C and the region A2 of the base surface 10a, and the light shielding film 30 is laminated on the phase shift film 20 in the region C. That is, a laminated structure of the phase shift film 20 and the light shielding film 30 is formed in the region C. Even in the laminated structure, the region C can be sufficiently shielded from light by the light shielding film 30. In addition, in the case of such a laminated structure, the entire mark 40 can be easily formed by wet etching described later. In the region C, only the light shielding film 30 may be formed without forming the phase shift film 20.

The phase shift film 20 shifts (changes) the phase of the light transmitted through the phase shift film. 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, since the light transmitted through the regions A1 and A2 and the light transmitted through the regions B1 and B2 need to interfere with each other, the phase shift film 20 needs to transmit exposure light. The phase shift film 20 containing Zr, si and N is sufficiently transparent to light having a wavelength of 250nm to 440nm, for example. In addition, as described below, with respect to the measurement marks 40 in which the phase shift film 20 including Zr, si, and N is formed in the areas A1 and A2, the defocus amount and the shift amount show a linear relationship in a wide range (refer to fig. 3 (c)). As a result, the detection of the defocus amount and the focus adjustment can be performed more easily and accurately using the phase shift mask 100.

The phase shift film 20 may further contain oxygen (O) in addition to zirconium (Zr), silicon (Si), and nitrogen (N). By containing oxygen (O), the transmittance of the phase shift film 20 to light having a wavelength of 250nm to 440nm is further improved. As a result, in the measurement mark 40 described later, the defocus amount and the shift amount show a linear relationship in a wider range (see fig. 3 (c)), and as a result, the defocus amount can be further detected and focus adjusted more easily and accurately using the phase shift mask 100.

In order to make the transmittance of the phase shift film 20 to light having a wavelength of 250nm to 400nm 25% or more, a preferred composition of the phase shift film 20 will be described in 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. When the atomic ratio (O/Zr) of the phase shift film (ii) is 0.1 or more, the atomic ratio (N/Zr) is preferably in the range of 0 to 3.0. (i) In either case, the atomic ratio (Si/Zr) is preferably 0.5 to 2.0 or 0.8 to 1.2.

The phase shift film 20 may contain elements other than Zr, si, N, and O, or may be a film substantially containing only Zr, si, N, and O. The phase shift film 20 may contain no element other than Zr, si, N, and O or in the form of a small amount of impurities to such an extent that the effect is not affected. In the present specification, the atomic ratio of the phase shift film 20 can be measured by using X-ray photoelectron spectroscopy (XPS) described in examples described below.

The higher the refractive index of the phase shift film 20, the more preferable. The following reasons may be mentioned as the reasons. By increasing the refractive index, the thickness of the phase shift film 20 derived from the expression d=λ/(2 (n-1)) (d: the thickness of the phase shift film 20, λ: the wavelength of the exposure light, and n: the refractive index of the phase shift film 20 at the wavelength λ) can be reduced. By reducing the thickness required for film formation, a film can be formed more uniformly on the substrate 10. In addition, if the film thickness can be reduced, the so-called undercut amount can be reduced, and a pattern closer to the design size can be obtained.

The lower the extinction coefficient (attenuation coefficient) of the phase shift film 20, the more preferable. The reason for this is that by decreasing the extinction coefficient, the light absorption decreases and the transmittance of the phase shift film 20 increases.

The refractive index of the phase shift film 20 in light having a wavelength of 302nm is 1.7 to 3.0, preferably a lower limit value of 1.75, and preferably an upper limit value of 2.9. The attenuation coefficient of the phase shift film 20 in light having a wavelength of 302nm is 0.6 or less, preferably 10 as a lower limit value ^-6 The upper limit is preferably 0.55. Here, in the phase shift mask 100, the transmittance of the portion of the substrate 10 where the phase shift film 20 is formed is referred to as "element transmittance", and the "element transmittance" may be referred to as external transmittance in consideration of reflection. The "element transmittance" is the transmittance of the substrate 10 and the phase shift film 20. When the phase shift film 20 has a film thickness that imparts a 180 ° phase shift to light having a wavelength of 302nm, the element transmittance to light having a wavelength of 302nm is preferably 25% or more, more preferably 40%, and still more preferably 60% or more.

The refractive index of the phase shift film 20 in light having a wavelength of 313nm is 1.7 to 3.0, preferably a lower limit value of 1.75, and preferably an upper limit value of 2.9. The attenuation coefficient of the phase shift film 20 in light having a wavelength of 313nm is 0.5 or less, preferably a lower limit of 10 ^-6 The upper limit value is preferably 0.45. When the phase shift film 20 has a film thickness that imparts a 180 ° phase shift to light having a wavelength of 313nm, the element transmittance to light having a wavelength of 313nm is preferably 30% or more, more preferably 40%, and still more preferably 60% or more.

The refractive index of the phase shift film 20 in light having a wavelength of 334nm is 1.7 to 3.0, preferably a lower limit value of 1.75, and preferably an upper limit value of 2.9. The attenuation coefficient of the phase shift film 20 in light having a wavelength of 334nm is 0.4 or less, preferably 10 as a lower limit value ^-6 Preferably, go upThe limit is 0.35. When the phase shift film 20 has a film thickness that imparts a 180 ° phase shift to light having a wavelength of 334nm, the element transmittance to light having a wavelength of 334nm is preferably 40% or more, more preferably 50%, and still more preferably 70% or more.

The refractive index of the phase shift film 20 in light having a wavelength of 365nm is 1.7 to 3.0, preferably a lower limit value of 1.72, and preferably an upper limit value of 2.85. The attenuation coefficient of the phase shift film 20 in light having a wavelength of 365nm is 0.2 or less, preferably 10 as a lower limit value ^-6 The upper limit is preferably 0.18. When the phase shift film 20 has a film thickness that imparts a 180 ° phase shift to light having a wavelength of 365nm, the element transmittance to light having a wavelength of 365nm is preferably 50% or more, more preferably 60%, and still more preferably 70% or more.

As described above, the phase shift film 20 preferably has a high transmittance of light having a wavelength of 250nm to 440nm used as exposure light in a projection exposure apparatus. Typical exposure light includes, for example, deep ultraviolet (DUV, wavelength: 302nm, 313nm, 334 nm), i-line (wavelength: 365 nm), h-line (wavelength: 405 nm), g-line (wavelength: 436 nm), and the like. For example, in the 1 st region and the 4 th region where the phase shift film 20 is disposed, the transmittance of light having a wavelength of 250nm to 440nm is preferably 25% or more, more preferably 30% or more, and still more preferably 40% or more. The transmittance of the 1 st region and the 4 th region corresponds to the element transmittance.

The thickness of the phase shift film 20 may be designed so that the phase difference between the light transmitted through the regions A1 and A2 and the light transmitted through the regions B1 and B2 is in an appropriate range (for example, 90 ° ± 50 °) in consideration of the optical characteristics such as the refractive index of the phase shift film 20 and the wavelength of the transmitted light (exposure light). For example, the thickness of the phase shift film 20 may be 40nm to 150nm.

As described above, in the present embodiment, by providing the phase shift film 20 in the areas A1 and A2, a phase difference is generated between the 1 st light transmitted through the areas A1 and A2 and the 2 nd light transmitted through the areas B1 and B2. On the other hand, as shown in fig. 18, by reducing the thickness of the regions B1 and B2 of the substrate 10 and providing a level difference (step difference) on the substrate surface 10a instead of providing the phase shift film 20, the same phase difference can be generated. However, the level difference provided on the substrate surface 10a is determined by the wavelength of the exposure light. For example, when a 90 DEG phase difference is obtained by using exposure light having a wavelength of 365nm, the step difference provided on the substrate surface 10a made of quartz glass (refractive index: 1.47) is 192nm. The step of the substrate surface 10a is formed by etching, for example, but it is very difficult to uniformly etch the step of 192nm. The reduction in the accuracy of the step processing may result in a reduction in the accuracy of defocus detection of the phase shift mask. In particular, the problem becomes more pronounced the larger the etched area, i.e. the larger the area of the phase shift mask, and the number of measurement marks 40.

In the phase shift mask 100 of the present embodiment, the phase shift film 20 is formed without forming a step on the substrate surface 10 a. The phase shift film 20 is relatively easy to form a uniform film thickness over a large area. Therefore, even in the case of increasing the area of the phase shift mask 100 to increase the number of measurement marks 40, the accuracy of defocus detection can be improved. For example, in the manufacture of large-area devices such as Flat Panel Displays (FPDs), large phase shift masks are required. The phase shift mask 100 of the present embodiment can be suitably used for manufacturing a large-area device such as an FPD.

[ method of manufacturing phase Shift mask ]

The method for manufacturing the phase shift mask 100 having the measurement marks 40 is not particularly limited, and a general method may be used. For example, the phase shift mask 100 may be manufactured using reactive sputtering and wet etching (refer to fig. 14 and 15) to form the measurement marks 40.

An example of a method for manufacturing the phase shift mask shown in fig. 14 and 15 will be described. First, a phase shift mask blank 150 having a base material 10 and a phase shift film 20 formed on the base material surface 10a is prepared (fig. 14 (a)). The phase shift mask blank 150 can be produced, for example, by forming the phase shift film 20 on the substrate surface 10a by reactive sputtering.

Measurement marks 40 are then formed (patterned). The formation of the measurement marks 40 may be formed using, for example, wet etching. First, a Cr film as the light shielding film 30 is formed 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 by spin coating on the light shielding film 30 to form a 1 st photoresist layer 51 (fig. 14 (b)). In fig. 14, an embodiment using a positive resist is shown, but a negative resist may be used.

The 1 st photo-resist layer 51 is exposed to light of a predetermined wavelength using the 1 st light-shielding mask. The light of a predetermined wavelength is not particularly limited, and light of a wavelength to which the resist is exposed may be, for example, 365nm light. The 1 st light shielding mask is patterned to cover the regions A1, A2, and C on the substrate surface 10a and expose the regions B1 and B2. Thus, the 1 st photoresist layer 51 on the areas B1 and B2 is exposed to light, thereby forming a1 st exposure portion 51E (fig. 14 (c)).

The 1 st photosensitive portion 51E is dissolved and removed by immersing the exposed substrate 10 in a developer (fig. 14 (d)). Next, the substrate 10 is immersed in an etching solution for the light shielding film 30. The light shielding film 30 on the regions B1 and B2 not covered with the 1 st photoresist layer 51 is thereby removed, exposing the phase shift film 20 (fig. 14 (e)).

The substrate 10 is immersed in an etching solution for the phase shift film 20. The phase shift film 20 on the areas B1 and B2 not covered with the 1 st photoresist layer 51 is thereby removed, exposing the substrate surface 10a (fig. 14 (f)).

Next, the substrate 10 is immersed in a resist stripping liquid. Thereby, the 1 st photoresist layer 51 remaining on the substrate 10 is dissolved and removed (fig. 15 (a)). After removing the 1 st photoresist layer 51, a2 nd photoresist layer 52 is formed over the entire substrate surface 10a (fig. 15 (b)). The 2 nd photoresist layer 52 may be formed using the same material as the 1 st photoresist layer 51 by the same method and may be made to have the same thickness.

The 2 nd photoresist layer 52 is exposed to light of a predetermined wavelength using the 2 nd light shielding mask. The 2 nd shadow mask forms a pattern in which the areas A1 and A2 on the substrate surface 10a are exposed. Thus, the 2 nd photoresist layer 52 on the areas A1, A2 is exposed to light, forming A2 nd exposure portion 52E (fig. 15 (c)).

The exposed substrate 10 is immersed in a developing solution. Thereby, the 2 nd exposure portion 52E is dissolved and removed (fig. 15 (d)). Next, the substrate 10 is immersed in an etching solution for the light shielding film 30. Thereby, the light shielding film 30 on the areas A1, A2 is removed, exposing the phase shift film 20 (fig. 15 (e)). Next, the substrate 10 is immersed in a resist stripping liquid. Thereby, the 2 nd photoresist layer 52 remaining on the substrate 10 is completely dissolved and removed (fig. 15 (f)). The phase shift mask 100 having the measurement marks 40 formed thereon as shown in fig. 15 (f) can be obtained by the above steps. Note that, although the wet etching shown in fig. 14 and 15 is described as the patterning method of the measurement mark 40, the present embodiment is not limited to this, and the measurement mark 40 may be patterned by a known method.

[ Structure and principle of action of measurement marker ]

The structure of the measurement mark 40 used in the present embodiment shown in fig. 1 will be described. As shown in fig. 1 (a), the measurement mark 40 is a "box-in-box" pattern composed of 2 substantially quadrangles. The measurement mark 40 is composed of an outer quadrangle (1 st mark) 41, and an inner quadrangle (2 nd mark) 42 concentric with the outer quadrangle 41 and disposed in the outer quadrangle 41. The outer quadrangle 41 is larger than the inner quadrangle 42. The outer quadrangle 41 includes, on the substrate surface 10a, lateral sides 411X and 412X extending in an X direction (an example of the "1 st arrangement direction") parallel to the substrate surface 10a, and longitudinal sides 411Y and 412Y extending in a Y direction (an example of the "2 nd arrangement direction") parallel to the substrate surface 10a and orthogonal to the X direction. The lateral sides 411x and 412x and the longitudinal sides 411y and 412y may be combined to form a complete quadrangle, or may be partially or completely separated to form a incomplete quadrangle. In the present embodiment, as shown in fig. 1 (a), the outer quadrangle 41 is a incomplete quadrangle.

The inner quadrangle 42 includes, on the substrate surface 10a, lateral sides 421X and 422X extending in the X direction, and longitudinal sides 421Y and 422Y extending in the Y direction. The lateral sides 421x and 422x and the longitudinal sides 421y and 422y may be combined to form a complete quadrangle, or may be partially or completely separated to form a partial quadrangle. In the present embodiment, as shown in fig. 1 (a), the inner quadrangle 42 is a incomplete quadrangle.

As shown in fig. 1 (B), the areas A1, B1, C, A2, and B2 are disposed adjacent to each other in this order along the X direction intersecting the phase shift film 20 and the light shielding film 30 in the vicinity of the longitudinal sides 411y and 412y of the outer quadrangle 41 and the longitudinal sides 421y and 422y of the inner quadrangle 42. That is, the measurement mark 40 has the basic configuration of the phase shift film 20 and the light shielding film 30 described above. However, the basic arrangement is oriented in the same direction near vertical edge 411y and near vertical edge 412y, and the basic arrangement is oriented in the opposite direction near vertical edge 412y and near vertical edge 422y. The basic arrangement is reversed in the vicinity of the longitudinal edge 411y and the vicinity of the longitudinal edge 421 y. On each of the vertical sides 411y and 412y (outer quadrangle 41), the region A1, the region B1, the region C, the region A2, and the region B2 are arranged adjacently in this order along the direction X1 (the direction from left to right in fig. 1B) from one side to the other side in the X direction. On the other hand, on the vertical sides 421y and 422y (inner quadrangle 42), the region A1, the region B1, the region C, the region A2, and the region B2 are arranged adjacently in this order along the direction X2 (the direction from right to left in fig. 1B) from the other side in the X direction.

In the vicinity of the lateral sides 411x and 412x of the outer quadrangle 41 and the lateral sides 421x and 422x of the inner quadrangle 42, the areas A1, B1, C, A2, and B2 are disposed adjacently in this order along the direction Y intersecting the phase shift film 20 and the light shielding film 30, but the disposed orientations are opposite. On each of the lateral sides 411x and 412x (outer quadrangle 41), the region A1, the region B1, the region C, the region A2, and the region B2 are arranged adjacently in this order along the direction Y1 (downward direction in fig. 1B) from one side to the other side in the Y direction. On the other hand, on the lateral sides 421x and 422x (inner quadrangle 42), the region A1, the region B1, the region C, the region A2, and the region B2 are arranged adjacently in this order along the direction Y2 (the direction from top to bottom in fig. 1B) from the other side in the Y direction.

In the present embodiment, as shown in fig. 1B, the outer side 41 (vertical side 411 y) and the inner side 42 (vertical side 421 y) share the region B2 existing therebetween as B2 of the respective basic arrangement. The outer side 41 (vertical side 412 y) and the inner side 42 (vertical side 422 y) share the area A1 existing therebetween as A1 of the respective basic configurations. Thereby enabling space saving of the mark 40. In addition, the width Wb2 of the region B2 existing between the outer quadrangle 41 and the inner quadrangle 42 needs to be a width that decomposes the aerial image of the region C contained in the outer quadrangle 41 and the inner quadrangle 42, respectively, as much as possible when projecting the exposure light to the measurement mark 40 (the phase shift mask 200). Therefore, the width Wb2 of the region B2 is preferably 2 times or more the width Wc of the region C of the outer quadrangle 41 or 2 times or more the width Wc of the region C of the inner quadrangle 42. The vertical sides 411y (pattern 1), 421y (pattern 2), 422y (pattern 3), and 412y (pattern 4) are referred to as "1 st portion", and the horizontal sides 411x (pattern 5), 421x (pattern 6), 422x (pattern 7), and 412x (pattern 8) are referred to as "2 nd portion".

As described above, in the outer quadrangle 41 and the inner quadrangle 42, the orientations of the arrangement of the region A1, the region B1, the region C, the region A2, and the region B2 in the X direction are opposite, and the orientations of the arrangement of the regions in the Y direction are also opposite. For the projection image passing through the projection optical system of the outer quadrangle 41 and the inner quadrangle 42, positional displacement occurs in mutually opposite directions on the same straight line in the projection plane according to the defocus amount.

For example, as shown in fig. 3 (a), when the focal point of the projection optical system is in focus, that is, when the defocus amount is 0 (zero), the center 41C of the projected image 41P of the outer quadrangle 41 coincides with the center 42C of the projected image 42P of the inner quadrangle 42 in the projected image 40P on the projection surface of the measurement mark 40 passing through the projection optical system. On the other hand, as shown in fig. 3 (b), in the projected image 40P, when the focus of the projection optical system is not in focus, that is, when defocus occurs, positional displacement occurs in the centers 41C and 42C.

On the premise that the reason for the occurrence of the positional shift is that, when the substrate is exposed to an arbitrary pattern through the photomask, when the emission angle (emission angle) of the light emitted from the photomask is perpendicular, the center position of the projected image of the pattern formed on the substrate at the time of defocusing is formed at substantially the same position as the center position of the projected image of the pattern formed on the substrate at the time of focusing. On the other hand, in the case where the emission angle of the light emitted from the photomask is an angle other than the vertical (90++α: α is an arbitrary angle), the center position of the projected image of the pattern formed on the substrate at the time of defocusing is formed at a position different from the center position of the projected image formed on the substrate at the time of focusing. The emission angle corresponds to the incidence angle of light incident on the substrate.

By forming the measurement mark 40, the formation region A1 and the formation region B1, and the formation region A2 and the formation region B2, the emission angle of the light emitted from the photomask can be made different from the vertical (90 ° ± α: α is an arbitrary angle). More specifically, the emission angle can be set to an angle different from the vertical by measuring the phase difference between the area A1 and the area B1 and the phase difference between the area A2 and the area B2 of the mark 40.

In the configuration 1 formed by the vicinity of the vertical side 411y and the vicinity of the vertical side 421y, since the arrangement of the marks in the vicinity of the vertical side 411y is opposite to that in the vicinity of the vertical side 421y, the emission angles of the light emitted through the areas A1 and B1, the areas A2 and B2 in the vicinity of the vertical side 411y and the emission angles of the light emitted through the areas A1 and B1, the areas A2 and B2 in the vicinity of the vertical side 421y are opposite to each other. As a result, when the projected images of the vertical sides 411y and 421y are formed at positions above the focal position in the Z-axis direction (direction opposite to the gravitational direction) with respect to the pattern images of the vertical sides 411y and 421y formed on the substrate (referred to as positive defocus), the projected images of the vertical sides 411y and 421y come close to each other; when the pattern of the vertical side 411y and the vertical side 421y is formed at a position lower than the focal position in the Z-axis direction (referred to as negative defocus), the vertical side 412y is separated from the projected image of the vertical side 421 y.

In the configuration 2 including the vicinity of the vertical side 412y and the vicinity of the vertical side 422y, the arrangement of the marks in the vicinity of the vertical side 412y and the vicinity of the vertical side 422y is different from that in the configuration 1. Thus, the pattern images of the vertical sides 412y and 422y formed on the substrate show a behavior opposite to that of the constitution 1. That is, with respect to the projected images of the vertical side 412y and the vertical side 422y formed on the substrate, the vertical side 412y is separated from the projected image of the vertical side 422y in the positive defocus, and the vertical side 412y is close to the projected image of the vertical side 422y in the negative defocus.

Using the principles described above, the projected images 40P of the outer quadrangle 41 and the inner quadrangle 42 are obtained. On the diagonal line L of the projection image 40P, the positional shift amount of the center 42C with respect to the center 41C is defined as "shift amount". When the offset is "positive", it means positive defocus, and when the offset is "negative", it means negative defocus. Fig. 3 (c) shows the relationship between the defocus amount and the offset amount of the projection image 40P of the measurement mark 40. The solid line represents a linear approximation of a straight line and the broken line represents an analog value. As can be seen from this, in the projection image 40P of the measurement mark 40, the defocus amount and the shift amount have a strong correlation, and a linear relationship is shown in a wide range. Therefore, the offset is measured, and the defocus amount is easily and accurately detected and the focus is adjusted based on the offset. Specifically, as shown in fig. 3 (a), when the center 41C coincides with the center 42C, the offset amount is 0 (zero). For example, as shown in fig. 3 (b), when the center 42C is shifted in the right-up direction with respect to the center 41C, the shift amount is "negative", and it is known that the defocus is negative. The offset amount may be calculated by the shortest distance between the center 41C and the center 42C, or the shortest distance may be decomposed into 2 components (X component, Y component) in the two-dimensional direction (X direction, Y direction) of the substrate.

In addition, for example, as shown in fig. 17 (a), the measurement mark 80 may be made in a substantially cross-shaped pattern. The measurement mark 80 is formed of 4 substantially L-shaped portions constituting an outer cross (1 st mark) 81, and 4 substantially L-shaped portions constituting an inner cross (2 nd mark) 82 concentric with the outer cross 81. In the vicinity of the outer cross 81 and the inner cross 82, the region A1, the region B1, the region C, the region A2, and the region B2 are arranged adjacently in this order along the X direction intersecting the light shielding film 30. For example, the X direction may be a direction orthogonal to the straight line portion of the measurement mark 80. As shown in fig. 17 (b) and (c), for projection images 81P, 82P passing through the projection optical system of the outer cross 81 and the inner cross 82, positional displacement occurs in mutually opposite directions on the same straight line L80 in the projection plane according to the defocus amount. Here, in the projection image 80P of the measurement mark 80, the positional shift amount of the center 82C with respect to the center 81C is defined as "shift amount". In the projection image 80P, the defocus amount and the shift amount also show a linear relationship. Therefore, the offset amount can be measured, and the defocus amount can be detected and the focus adjusted based on the offset amount.

In addition, the measurement indicia 40 may not be the only in-box structure of fig. 1. For example, the outer structure may be a quadrangle (the corners may not be connected), and the inner structure may be a cross. With this configuration, in fig. 3, the offset is calculated by measuring the distance between 2 reference positions with reference to the position of the center 41C of the outer quadrangle and the position of the center 42C of the inner quadrangle. Similarly, the offset can be calculated by determining the reference position in the outer pattern and the reference position in the inner pattern, and measuring the distance between the 2 reference positions. Therefore, the shape of the outside-inside measurement mark 40 can be appropriately designed.

[ defocus amount detection method and Focus adjustment method ]

The method of detecting the defocus amount and the method of adjusting the focus in the projection exposure apparatus using the phase shift mask 100 having the measurement marks 40 will be described with reference to the flowchart shown in fig. 4.

First, an exposure apparatus 500 shown in fig. 5 for performing 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 holding the phase shift mask 100, a mask stage driving mechanism 507, a substrate stage 505 holding a photosensitive substrate 515 as an exposure target, and a substrate stage driving mechanism 506. The exposure apparatus 500 further includes a main controller 509 for controlling the entire exposure apparatus 500 including the mask stage driving mechanism 507, the projection optical system controller 508, and the substrate stage driving mechanism 506. The projection optical system controller 508 controls driving elements corresponding to the respective lens elements constituting the projection optical system 504, and can adjust the positions and angles of the respective lens elements. The mask stage driving mechanism 507 can move the mask stage 503 in the horizontal plane and in the optical axis direction of the projection optical system 504. The substrate stage driving mechanism 506 can move the substrate stage 505 in the horizontal plane and the optical axis direction.

The mask stage driving mechanism 507 and the substrate stage driving mechanism 506 can also adjust the slopes 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 can finely adjust the interval between the phase shift mask 100 and the photosensitive substrate 515 in the optical axis direction, that is, can perform focus adjustment. In addition, the projection optical system controller 508 can perform focus adjustment by fine adjustment of at least one position and/or slope of a lens constituting 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 are focus adjusting mechanisms in the exposure apparatus 500. The focus adjustment mechanism is controlled by the main controller 509.

A method of detecting the defocus amount in the exposure apparatus 500 (steps S1 to S3 in fig. 4) will be described. First, in the exposure apparatus 500 shown in fig. 5, the phase shift mask 100 is arranged on the mask stage 503. A photosensitive substrate 515 coated with a photoresist is disposed on the substrate stage 505.

Next, the measurement mark 40 of the phase shift mask 100 is projected onto the photosensitive substrate 515 and exposed (step S1 in fig. 4). First, exposure light is emitted from a light source LS of the exposure apparatus 500. As the illumination light, for example, deep ultraviolet (DUV, 302nm, 313nm, 334 nm), i-line (365 nm), h-line (405 nm), g-line (436 nm), and the like are used. The emitted exposure light enters the illumination optical system 502, is adjusted to a predetermined beam, and irradiates the phase shift mask 100 held on the mask stage 503. The light passing through the phase shift mask 100 has a pattern of the measurement mark 40 drawn on the phase shift mask 100, and the pattern is irradiated to a predetermined position on the surface (projection surface) of the photosensitive substrate 515 held on the substrate stage 505 by the projection optical system 504. Thus, the measurement mark 40 of the phase shift mask 100 is imagewise exposed on the photosensitive substrate 515 at a predetermined magnification.

Next, the positional shift amount (offset amount) of the center 42C with respect to the center 41C is measured in the projection image 40P of the measurement mark 40 exposed on the photosensitive substrate 515 (see fig. 3 b) (step S2 of fig. 4). The offset amount can be measured by observing the projection image 40P of the measurement mark 40 with an optical microscope, for example.

Then, the defocus amount is calculated from the measured offset amount (step S3 of fig. 4). As described above, since the defocus amount and the offset amount show a linear relationship (see fig. 3 (c)), the defocus amount can be easily and accurately calculated from the measured offset amount. Regarding the relationship between the defocus amount and the offset amount shown in fig. 3 (c), for example, the data may be obtained by performing simulation, experiment, or the like before the detection of the defocus amount described above (steps S1 to S3 in fig. 4).

Next, a focus adjustment method in the exposure apparatus 500 (steps S1 to S4 in fig. 4) will be described. First, the defocus amount is detected by the above method (steps S1 to S3 of fig. 4). Next, based on the detected defocus amount, focus adjustment is performed by the focus adjustment mechanism (506, 507, 508) of the exposure apparatus 500 in such a manner that the defocus amount is corrected (eliminated) (step S4 of fig. 4). Specifically, for example, fine adjustment of the slope of the mask stage 503 and/or the substrate stage 505 and the position in the optical axis direction may be performed by the mask stage driving mechanism 507 and/or the substrate stage driving mechanism 506, fine adjustment of the interval between the phase shift mask 100 and the photosensitive substrate 515 in the optical axis direction may be performed, and focus may be adjusted. In addition to or instead of this, the focus adjustment may be performed by fine adjustment of at least one position and/or gradient of a lens constituting the projection optical system 504 by the projection optical system controller 508.

The detection of the defocus amount and the focus adjustment described above may be performed before a photolithography process using an exposure apparatus in manufacturing devices such as semiconductors and liquid crystal panels. That is, the device can be manufactured by performing exposure using the projection optical system adjusted by the above-described focus adjustment method. By using the projection optical system with the focus adjusted, the circuit pattern defect in the exposure process can be reduced, and the device can be manufactured efficiently.

Modification example

In the above embodiment, the defocus amount detection method and the focus adjustment using 1 measurement mark 40 have been described, but the present embodiment is not limited to this. For example, in the phase shift mask 100 of the present embodiment, only 1 measurement mark 40 may be provided, or a plurality of measurement marks 40 may be provided. In addition, only 1 measurement mark 40 may be exposed on the photosensitive substrate 515, or a plurality of measurement marks 40 may be exposed.

In the above-described embodiment, the projection exposure apparatus 500 shown in fig. 5 in which only 1 projection optical system is mounted is used, but the present embodiment is not limited to this. For example, even in a projection exposure apparatus equipped with a plurality of projection optical systems, or a so-called multi-lens exposure apparatus disclosed in japanese patent application laid-open No. 2018-54847, the defocus amount detection and focus adjustment can be performed similarly using the phase shift mask 100. In this case, as described below, the detection of the defocus amount and the focus adjustment of each projection optical system can be performed simultaneously using a plurality of measurement marks. The multi-lens exposure apparatus is suitable for exposure of a large area, and is used for exposure of a Thin Film Transistor (TFT) circuit pattern in the manufacture of Flat Panel Displays (FPDs) such as liquid crystal/organic EL displays.

In this modification, an example of a defocus amount detection method and a focus adjustment method in a multi-lens exposure apparatus using the phase shift mask 200 provided with the plurality of measurement marks 40 shown in fig. 6 (a) will be described. The multi-lens exposure apparatus used in the present modification example has 3 projection optical systems PL1 to PL3. The multi-lens exposure apparatus used in this modification is a step scanner (scanner). That is, the measurement marks 40 formed on the phase shift mask 200 are exposed on the photosensitive substrate by driving the phase shift mask 200 and the photosensitive substrate in the same direction (X direction) with respect to the projection optical systems PL1 to PL3 at the same speed. The other basic configuration is the same as the exposure apparatus 500 shown in fig. 5.

An example of a defocus amount detection method (steps S1 to S3 in fig. 4) will be described. First, a phase shift mask 200 shown in fig. 6 (a) is arranged in a multi-lens exposure apparatus. The phase shift mask 200 is provided with a plurality of measurement marks 40 on the substrate surface 10a of the substrate 10. The other structures are the same as the phase shift mask 100 shown in fig. 1. On the substrate surface 10a of the phase shift mask 200, three columns M1, M2, M3 constituted by a plurality of measurement marks 40 arranged in the X direction are arranged in the Y direction orthogonal to the X direction. In addition, a photosensitive substrate 215 is also provided in the multi-lens exposure apparatus.

Next, the measurement mark 40 of the phase shift mask 200 is projected onto the photosensitive substrate 215, and exposure is performed (step S1 in fig. 4). First, the mask stage and the substrate stage are driven synchronously in the X direction according to an instruction from a control device of the multi-lens exposure apparatus, and scanning exposure is performed on the 1 st irradiation region 215A and the 2 nd irradiation region 215B on the photosensitive substrate 215. Thereby, the columns M1P, M2P, M P of the 3 measurement mark images shown in fig. 6 (b) are formed on the substrate 215. The column M1P, M2P, M P is constituted by the images 40P of the plurality of measurement marks 40 arranged in the X direction. At the end of the scanning exposure for the 1 st irradiation region 215A and the 2 nd irradiation region 215B, the control device moves the substrate stage 505 to a position (step) corresponding to the 3 rd irradiation region 215C and the 4 th irradiation region 215D. Thereafter, scanning exposure is performed on the 3 rd irradiation region 215C and the 4 th irradiation region 215D. Thereby, 3 columns M11P, M12P, M P of measurement mark images are further formed on the substrate 215. In this way, the photosensitive substrate 215 is exposed by the projection images 41P of the plurality of measurement marks 40. The line M1P, M P of the measurement marker image is formed by the projection optical system PL1, the line M2P, M P of the measurement marker image is formed by the projection optical system PL2, and the line M3P, M13P of the measurement marker image is formed by the projection optical system PL 3.

Next, the amount of shift of the projected image 40P of the measurement mark 40 exposed to the photosensitive substrate 215 is detected (step S2 of fig. 4), and the defocus amount is calculated based on the detected amount of shift (step S3 of fig. 4). In this modification, the defocus amount may be detected for each projection image of the plurality of marks 40 formed on the photosensitive substrate 215. In fig. 6 (c), the relationship between the position (position in the X direction) of the projection image 40P on the photosensitive substrate 215 and the defocus amount (Z direction) at that position is shown with respect to the line M1P, M2P, M P of the 3 measurement mark images, with the center of the figure being the intersection of the center of the X axis and the center of the Y axis of the photosensitive substrate 215. As described above, in this modification, the defocus amount on the entire surface of the photosensitive substrate 215 can be detected at the same time. It should be noted that the phase shift mask 200 may have more than 1 measurement mark 40 and a pattern for manufacturing the device.

Next, an example of the 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 on the entire surface of the photosensitive substrate 215 by the above method (steps S1 to S3 in fig. 4). Next, focus adjustment of each projection optical system is performed based on the detected defocus amount (step S4 of fig. 4). As for the focus adjustment, based on the detected defocus amount, the focus adjustment is performed by the focus adjustment mechanism of each projection optical system in such a manner that the defocus amount is corrected (eliminated) independently, similarly to the projection exposure apparatus 500 (step S4 of fig. 4).

In this modification, since the defocus amount can be detected simultaneously on the entire surface of the photosensitive substrate 215, the focus adjustment can be effectively performed. Fig. 6 d shows the detection result of detecting the same defocus amount again after focus adjustment (steps S1 to S3 in fig. 4). As can be seen from fig. 6 (c) and (d), the focus is optimized over a wide range of the surface of the photosensitive substrate 615.

According to the defocus amount detection method and the focus adjustment method of the present modification, the defocus amount detection and the focus adjustment can be effectively performed in a wide range on the surface of the photosensitive substrate 215. Therefore, the defocus amount detection method and the focus adjustment method according to the present modification can be suitably used in the manufacture of the FPD for performing large-area exposure. In the manufacture of FPDs, if defocus occurs during exposure of TFT circuit patterns, line width errors affecting the electrical characteristics of the TFT circuit patterns may occur, and the quality of the display panel as a finished product may deteriorate. The defocus amount detection method and focus adjustment method according to the present modification can easily and accurately optimize the focus on the entire photosensitive substrate, and thus can suppress quality degradation of such a finished product (display panel).

In addition, a resolution map 45 may be provided together with the measurement marks 40. By providing the resolution map 45, the line width that can be exposed by the projection exposure apparatus can be confirmed. The resolution map 45 may have only 1 line width, or may have 2 or more different line widths. The resolution map may be disposed on the entire substrate in the same manner as the measurement mark 40 in fig. 6. This allows the line width of the projection exposure apparatus that can be exposed at each position on the entire substrate to be checked.

In the above embodiment and modification, the phase shift mask 100 for defocus inspection in which the measurement mark 40 is formed was described as an example, but other patterns such as a circuit pattern (device pattern) for exposing a photosensitive substrate and an alignment mark required for alignment may be formed on the mask. In this case, the phase shift film 20 may be formed at both the detection mark and the device pattern. The phase shift film 20 may be a phase shift mask having a device pattern without the detection mark 40. In this case, the phase shift film 20 may form a device pattern.

Examples

The phase shift mask (detection element), defocus amount detection method, and focus adjustment method are specifically described below by examples and comparative examples, but the present invention is not limited to these examples and comparative examples.

Formation of phase shift film

[ phase-shift film PS1]

The phase shift film PS1 is formed by reactive sputtering. First, a circular parallel flat plate (size: diameter 3 inches, thickness 0.5 mm) of quartz glass was prepared as the base material 10. Ar-N was introduced while using a DC magnetron sputtering apparatus and a ZrSi alloy target as a sputtering target ₂ The mixed gas was subjected to reactive sputtering by the capacitive coupling magnetron DC plasma method to form a phase shift film PS1 having a thickness of 100 nm. The composition (atomic ratio) of the ZrSi alloy target is Zr: si=1:2. Regarding the film forming conditions, the total pressure of the mixed gas was set to 0.3Pa, the Ar flow rate was set to 47.5sccm, and N ₂ The flow rate was 2.5sccm and the DC output power was 1.5kw.

[ phase shift films PS2 to PS5]

Except for changing Ar-N as shown in FIG. 7 ₂ Ar flow and N of the mixed gas ₂ Except for the ratio of the flow rates, phase shift films PS2 to PS5 are formed on the substrate 10 by the same method as the phase shift film PS1.

[ phase-shift film PS11]

Using Ar-N ₂ -O ₂ Mixed gas to replace Ar-N ₂ The phase shift film PS11 is formed on the substrate 10 by the same method as the phase shift film PS1 except that the gas is mixed. Regarding the film forming conditions, the total pressure of the mixed gas was set to 0.3Pa, the Ar flow rate was set to 30sccm, and N ₂ The flow rate is 19sccm, O ₂ The flow rate was 1sccm and the DC output power was 1.5kw.

[ phase-shift films PS12 to PS14]

Except that the Ar flow rate, N of the mixed gas was changed as shown in FIG. 7 ₂ Flow rate, O ₂ Except for the ratio of the flow rates, phase shift films PS12 to PS14 are formed on the substrate 10 by the same method as the phase shift film PS 11.

Evaluation of physical Properties of phase Shifting film

(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 is through Ar ⁺ The surface of each phase shift film was etched by ion sputtering to about 10nm, and then measured.

(2) Simulation of refractive index, attenuation coefficient, film thickness, and element transmittance

The refractive indices and attenuation coefficients of the phase shift films PS1 to PS5 and PS11 to PS14 were measured by ellipsometry at 6 wavelengths (DUV (wavelengths 302nm, 313nm, 334 nm), i-line (365 nm), h-line (405 nm), g-line (436 nm)). From the measurement results of the refractive index, the film thicknesses of the phase shift films PS1 to PS5 and PS11 to PS14 to which the 90 degree phase shift was applied were calculated at 6 wavelengths, respectively. Further, the transmittance (element transmittance) of the elements (base material and phase shift film) on which the phase shift films PS1 to PS5 and PS11 to PS14 having the calculated film thicknesses were formed was calculated by simulation. The simulation was performed using simulation software "TFCalc", and based on the measurement results of refractive index and extinction coefficient at 6 wavelengths obtained by ellipsometry, the transmission rates of the phase shift films PS1 to PS5 and PS11 to PS14 at the film thicknesses were calculated using film thicknesses at which a phase shift of 90 ° was applied at each wavelength. Here, the transmittance is an external transmittance (element transmittance) taking reflection into consideration. Fig. 8 to 13 show the measured refractive index and attenuation coefficient, and the calculated film thickness and element transmittance.

Fabrication of phase shift mask blank 150

To simulate the measurement marks 40 of the box-in-box pattern provided on the phase shift mask 100 shown in fig. 1, two kinds of phase shift mask blanks 150a and 150b were fabricated, and physical property values of the phase shift film 20 were obtained. The phase shift mask blank 150a uses the phase shift film PS4 described above. The phase shift mask blank 150b uses the phase shift film PS13 described above.

< production of phase-shift mask blank 150a >

First, a square parallel flat plate (size: 6 inches on one side, thickness 0.25 inches) of quartz glass was prepared as a base material 10. A phase shift film PS4 having the composition shown in fig. 7 was formed as the phase shift film 20 on the base material 10 by the reactive sputtering described above. The film thickness of the phase shift film PS4 was set to be 51.6nm (fig. 14 (a)) which shows a phase shift of 90 ° with respect to light having a wavelength of 365nm as shown in fig. 11.

< production of phase-shift mask blank 150b >

A phase shift mask 150b was fabricated in the same manner as the phase shift 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 120.7nm, which showed a phase shift of 90℃with respect to light having a wavelength of 365nm as shown in FIG. 11.

< design of phase shift masks 100A and 100B >

For the fabricated phase shift mask blanks 150A and 150B, phase shift masks 100A and 100B are designed, which phase shift masks 100A and 100B are provided with measurement marks 40 of the box-in-box pattern shown in fig. 1. The dimensions (design values) of the measurement marks 40 formed on the phase shift masks 100A and 100B are as follows.

Width of the outer quadrangle 41 in the X direction and width in the Y direction: x:90 μm, Y:90 μm

Width of the inner quadrangle 42 in the X direction and width in the Y direction: x:46 μm, Y:46 μm

Width (Wc) of transverse edges 411x, 412x, 421x, 422x and longitudinal edges 411y, 412y, 421y, 422 y: width of 8 μm region A1 (Wa 1): 16 μm

Width of area A2 (Wa 2): 1 μm

Width (Wb 1) of region B1: 1 μm

Width (Wb 2) of the region B2 existing between the outer quadrangle 41 and the inner quadrangle 42: 16 μm

Here, the width of the outer quadrangle 41 in the X direction means the length from one end to the other end of the outer quadrangle 41 in the X direction, and the width in the Y direction means the length from one end to the other end of the outer quadrangle 41 in the Y direction. Similarly, the width of the inner quadrangle 42 in the X direction means the length from one end to the other end of the inner quadrangle 42 in the X direction, and the width in the Y direction means the length from one end to the other end of the inner quadrangle 42 in the Y direction.

< simulation of relation of offset to defocus amount >

Using the refractive index, attenuation coefficient, film thickness, element transmittance, and design value of the measurement mark measured by the fabricated phase shift mask blank 150A, the phase shift mask 100A was placed in a projection exposure apparatus, light having a wavelength of 365nm was projected via a projection optical system, and the relationship between the offset amount and defocus amount was simulated for the obtained projection image 40P (see fig. 3 (a) and (b)). The results are shown in FIG. 16. Similarly, the relationship between the shift amount and the defocus amount was also simulated for the phase shift mask 100B. The results are shown together in fig. 16.

As shown in fig. 16, in the measurement marks 40 of the phase shift masks 100A and 100B, the offset amount and the defocus amount show a linear relationship in a wide range. In the region where the offset amount and the defocus amount show a linear relationship, for example, the offset amount of the measurement mark 40 can be measured by an optical microscope and the defocus amount can be easily and accurately calculated based on the measurement mark. And focus adjustment can be easily performed in the projection exposure apparatus to correct (eliminate) the defocus amount. In this way, the phase shift masks 100A and 100B function as detection elements for detecting the defocus amount of the light transmitted through the projection optical system.

In fig. 16, simulation results of the phase shift masks 100A and 100B are compared. The shift amount and defocus amount of the phase shift mask 100B using the phase shift film PS13 show a linear relationship in a wider range than the phase shift mask 100A using the phase shift film PS 4. Therefore, the shift mask 100B can detect a larger defocus amount. The phase shift mask 100A can detect a defocus amount in the range of-30 μm to +15 μm, whereas the phase shift mask 100B can detect a defocus amount in the wider range of-30 μm to +25 μm. As one of the reasons for this, as shown in fig. 11, it is presumed that the element transmittance (94.08%) of the phase shift film PS13 used in the phase shift mask 100B is higher than the element transmittance (56.94%) of the phase shift film PS4 used in the phase shift mask 100A for 365nm light. The element transmittance corresponds to the transmittance in the areas A1 and A2 of the phase shift masks 100A, 100B. The reason why the element transmittance (94.08%) of the phase shift film PS13 is higher than the element transmittance (56.94%) of the phase shift film PS4 is that the atomic ratio (O/Zr) of oxygen (O) to zirconium (Zr) in the phase shift film PS13 is higher than in the phase shift film PS 4. If the atomic ratio (O/Zr) is increased, the band gap of the film material becomes large, and the attenuation coefficient decreases. Thus, the transmittance is improved.

As shown in fig. 7, the phase shift films PS1 to PS5 do not introduce oxygen during film formation. Therefore, in the phase shift films PS1 to PS5, the atomic ratio (O/Zr) of oxygen (O) to zirconium (Zr) is less than 0.1. The oxygen contained in the phase shift films PS1 to PS5 is not actively introduced, but is oxygen in the air taken in by oxidation. On the other hand, the phase shift films PS11 to 14 actively introduce oxygen during film formation. Therefore, in the phase shift films PS11 to PS14, the atomic ratio (O/Zr) of oxygen (O) to zirconium (Zr) is 0.1 or more.

The physical properties of the phase shift films PS1 to PS5 and PS11 to PS14 shown in FIG. 11 in 365nm light (i-line) were compared. The element transmittance of the phase shift films PS11 to PS14 having an atomic ratio (O/Zr) of 0.1 or more is higher than that of the phase shift films PS1 to PS5 having an atomic ratio (O/Zr) of less than 0.1. The phase shift films PS11 to PS14 having an atomic ratio (O/Zr) of 0.1 or more exhibit sufficiently high transmittance for 365nm light (i-line). From the result, it was estimated that the phase shift mask 100 using the phase shift films PS11 to PS14 having an atomic ratio (O/Zr) of 0.1 or more was excellent as a detection element for the defocus amount of the projection optical system when 365nm light (i-line) was used. 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.

In addition, among the phase shift films PS1 to PS5 having an atomic ratio (O/Zr) of less than 0.1, for example, the element transmittance is higher for the phase shift films PS3 to PS5 having an atomic ratio (Si/Zr) of 1.00 to 1.20 and an atomic ratio (N/Zr) of 2.1 to 2.6 than for the phase shift films PS1 and PS2 having an atomic ratio (Si/Zr) and an atomic ratio (N/Zr) out of the above ranges. From the results, it was estimated that the phase shift mask 100 using the phase shift films PS3 to PS5 having 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 used sufficiently as a detection element for the defocus amount of the projection optical system when 365nm light (i-line) is used.

The phase shift films PS1 to PS5 and PS11 to PS14 show the same tendency as the element transmittance for 365nm light shown in fig. 11 even for light of wavelengths other than 365nm shown in fig. 8 to 10 and 12 to 13. Therefore, it is assumed that the phase shift films PS3 to PS5 and PS11 to PS14 can be sufficiently used for detection elements of defocus amounts of projection optical systems in the case of using light of wavelengths 302nm (DUV, fig. 8), 313nm (DUV, fig. 9), 334nm (DUV, fig. 10), 405nm (h-line, fig. 12) and 436nm (g-line, fig. 13).

The phase shift films PS3 to PS5 and the phase shift films PS11 to PS14 used in the present embodiment can be used for a phase shift mask having both a detection mark and a device pattern, and in this case, both a detection mark and a device pattern can be formed. In addition, the phase shift films PS3 to PS5 and the phase shift films PS11 to PS14 can be used also for a phase shift mask having a device pattern without a detection mark, and in this case, a device pattern can be formed.

Industrial applicability

The phase shift mask 100 of the present embodiment can be used as a detection element of the defocus amount of the projection optical system. The phase shift mask 100 of the present embodiment is not limited to an exposure apparatus, and may be used as a detection element for a defocus amount of an optical measuring machine, a laser processing machine, or the like.

Symbol description

10 substrate

20 phase shift film

30 shading film

40 measurement indicia

100. 200 phase shift mask

500 exposure device

LS light source

502 illumination optical system

504 projection optical system

508 projection optical system controller

503 mask carrier

507 mask stage driving mechanism

505 substrate carrier

506 substrate carrier driving mechanism

509 main controller

A1 Area of the substrate surface (area 1)

A2 Area of the substrate surface (area 4)

B1 Area of the substrate surface (area 2)

B2 Area of the substrate surface (5 th area)

C area of the substrate surface (area 3)

Claims

1. A phase shift mask, having:

a substrate;

a1 st semi-permeable layer and a2 nd semi-permeable layer; and

the light-shielding layer is arranged on the surface of the substrate,

a measurement mark having a pattern in which the following regions are adjacently arranged along an arrangement direction parallel to the surface is formed on the surface of the base material:

a1 st region provided with a1 st semi-permeable layer;

a2 nd region of the substrate surface exposed;

A 3 rd region in which the light shielding layer is disposed;

a 4 th region provided with a 2 nd semi-permeable layer; and

and the 5 th area of the surface of the substrate is exposed.

2. The phase shift mask of claim 1, wherein,

the measuring mark has a 1 st part in which the 1 st pattern, the 2 nd pattern, the 3 rd pattern, and the 4 th pattern are arranged in order along the 1 st arrangement direction,

in the pattern 1 and the pattern 4, the 1 st region, the 2 nd region, the 3 rd region, the 4 th region, and the 5 th region are arranged in order from one side toward the other side in the arrangement direction 1 st,

in the pattern 2 and the pattern 3, the 1 st region, the 2 nd region, the 3 rd region, the 4 th region, and the 5 th region are arranged in order from the other side toward one side of the arrangement direction 1 st.

3. The phase shift mask of claim 2, wherein,

the measurement mark has a 5 th pattern, a 6 th pattern, a 7 th pattern, and a 2 nd portion of the 8 th pattern arranged in order along a 2 nd alignment direction different from the 1 st alignment direction,

in the 5 th and 8 th patterns, the 1 st, 2 nd, 3 rd, 4 th, and 5 th regions are arranged in order from one side toward the other side of the arrangement direction of the 2 nd,

In the pattern 6 and the pattern 7, the 1 st region, the 2 nd region, the 3 rd region, the 4 th region, and the 5 th region are arranged in order from the other side toward one side of the arrangement direction 2 nd.

4. A phase shift mask as claimed in claim 3, wherein the measurement mark has the 1 st and 2 nd portions.

5. The phase shift mask according to any one of claims 1 to 4, wherein a width of the 2 nd region and a width of the 4 th region are smaller than a width of the 3 rd region in the arrangement direction.

6. The phase shift mask according to any one of claims 1 to 5, wherein,

the measurement mark has a 1 st mark formed by the pattern and a 2 nd mark formed by the pattern,

the 1 st mark is larger than the 2 nd mark.

7. The phase shift mask of claim 6, wherein the 1 st mark or the 2 nd mark is substantially quadrilateral.

8. The phase shift mask of claim 6 or 7, wherein the 1 st mark or the 2 nd mark is substantially cross-shaped.

9. The phase shift mask according to any one of claims 1 to 8, wherein a phase difference between the 1 st light transmitted through the 1 st and 4 th regions and the 2 nd light transmitted through the 2 nd and 5 th regions is 90 ° ± 50 ° when the measurement mark is irradiated with light of a predetermined wavelength.

10. The phase shift mask of claim 9, wherein the 1 st light and the 2 nd light have a phase difference of 90 ° ± 20 °.

11. The phase shift mask of claim 10, wherein the 1 st light and the 2 nd light have a phase difference of 90 ° ± 5 °.

12. The phase shift mask of any of claims 1 to 11, wherein the 1 st and 2 nd semi-permeable layers comprise zirconium (Zr), silicon (Si), and nitrogen (N).

13. The phase shift mask of claim 12, wherein the 1 st semi-transmissive layer and the 2 nd semi-transmissive layer further comprise oxygen (O).

14. The phase shift mask according to claim 13, wherein an atomic ratio O/Zr of the oxygen to the zirconium is 0.1 or more in the 1 st semi-transmissive layer and the 2 nd semi-transmissive layer.

15. The phase shift mask of claim 14, wherein,

in the 1 st semi-permeable layer and the 2 nd semi-permeable layer,

the atomic ratio Si/Zr of the silicon relative to the zirconium is 0.8-1.2,

the atomic ratio N/Zr of the nitrogen to the zirconium is 0.04-2.3,

the atomic ratio O/Zr of oxygen to zirconium is 0.1-3.4.

16. The phase shift mask of claim 12, wherein,

in the 1 st semi-permeable layer and the 2 nd semi-permeable layer,

The atomic ratio Si/Zr of the silicon relative to the zirconium is 1.00-1.20,

the atomic ratio N/Zr of the nitrogen to the zirconium is 2.1-2.6.

17. The phase shift mask of claim 16, wherein,

in the 1 st semi-permeable layer and the 2 nd semi-permeable layer,

the atomic ratio O/Zr of oxygen with respect to the zirconium is less than 0.1.

18. The phase shift mask of any of claims 1 to 17, wherein the refractive index of the 1 st and 2 nd semi-transmissive layers in light of wavelength 365nm is 1.7-3.0.

19. The phase shift mask according to any one of claims 1 to 18, wherein the attenuation coefficient of the 1 st and 2 nd semi-transmissive layers in light having a wavelength of 365nm is 0.2 or less.

20. The phase shift mask of any one of claims 1 to 19, wherein the phase shift mask has a resolution map.

21. The phase shift mask of any one of claims 1 to 20, wherein the measurement mark has a plurality.

22. The phase shift mask according to any one of claims 1 to 21, wherein transmittance of the 1 st region and the 4 th region with respect to light having a wavelength of 250nm to 440nm is 25% or more.

23. The phase shift mask according to any one of claims 1 to 22, wherein,

The 2 nd semi-permeable layer is continuously formed throughout the 3 rd and 4 th regions of the substrate surface,

in the 3 rd region, the light shielding layer is laminated on the 2 nd semi-transmissive layer.

24. A detection element for detecting a defocus amount of light of a predetermined wavelength transmitted through a projection optical system, the detection element comprising:

a substrate;

a 1 st semi-permeable layer and a 2 nd semi-permeable layer; and

the light-shielding layer is arranged on the surface of the substrate,

a 1 st region provided with a 1 st semi-permeable layer;

a 2 nd region of the substrate surface exposed;

a 3 rd region in which the light shielding layer is disposed;

a 4 th region provided with a 2 nd semi-permeable layer; and

and the 5 th area of the surface of the substrate is exposed.

25. The detecting element of claim 24, wherein,

26. The detecting element of claim 25, wherein,

27. The test element of claim 26, wherein the measurement indicia has the 1 st and 2 nd portions.

28. The detecting element according to any one of claims 24 to 27, wherein a width of the 2 nd region and a width of the 4 th region are smaller than a width of the 3 rd region in the arrangement direction.

29. The detecting element according to any one of claims 24 to 28, wherein,

the 1 st mark is larger than the 2 nd mark.

30. The detector element of claim 29 wherein the 1 st or 2 nd indicia is generally quadrilateral.

31. The test element of claim 29 or 30, wherein the 1 st mark or the 2 nd mark is substantially cross-shaped.

32. The detecting element according to any one of claims 24 to 31, wherein a phase difference between the 1 st light transmitted through the 1 st and 4 th regions and the 2 nd light transmitted through the 2 nd and 5 th regions is 90 ° ± 50 ° when the light of a predetermined wavelength is irradiated to the measurement mark.

33. The detecting element of claim 32, wherein the phase difference of the 1 st light and the 2 nd light is 90 ° ± 20 °.

34. The detecting element of claim 33, wherein the phase difference of the 1 st light and the 2 nd light is 90 ° ± 5 °.

35. The detection element according to any one of claims 24 to 34, wherein transmittance of the 1 st region and the 4 th region with respect to light having a wavelength of 250nm to 440nm is 25% or more.

36. A defocus amount detection method, which is a method of detecting a defocus amount of a projection optical system using the phase shift mask according to any one of claims 1 to 23 or the detection element according to any one of claims 24 to 35, comprising:

irradiating the phase shift mask or the detection element with light having a predetermined wavelength, and forming a projection image based on the measurement mark of the projection optical system on a projection surface;

measuring the position offset of the projection image of the measurement mark from a prescribed position in the projection surface; and

the defocus amount is calculated from the measured positional deviation amount.

37. The method of detecting a defocus amount according to claim 36, wherein a photosensitive substrate is provided on the projection surface, and the photosensitive substrate is exposed by using the pattern of the measurement mark.

38. A focus adjustment method of a projection optical system, comprising:

detecting a defocus amount of the projection optical system by the defocus amount detection method of claim 36 or 37; and

the focus of the projection optical system is adjusted based on the detected defocus amount.

39. A device manufacturing method comprising exposing a photosensitive substrate in a prescribed pattern using the projection optical system adjusted by the focus adjustment method of claim 38.