Phase-shift masks for extreme ultraviolet lithography

Abstract

A phase shift mask for an extreme ultraviolet lithography process comprises a substrate, a reflective layer on the substrate, a cover layer on the reflective layer, and a phase shift pattern on the cover layer. Each of the phase shift patterns may include a lower absorption pattern on the cover layer and an upper absorption pattern on the lower absorption pattern. The refractive index of the upper absorption pattern may be higher than the refractive index of the lower absorption pattern, and the thickness of the upper absorption pattern may be less than the thickness of the lower absorption pattern.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims the priority benefit of Korean Patent Application No. 10-2020-0045379 filed on April 14, 2020 in the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to a mask for an extreme ultraviolet lithography process, and more particularly to a phase-shift mask for an extreme ultraviolet lithography process. Background Art

[0004] The reduction in the size and design rules of semiconductor devices has increased the demand for technology to reduce the size of patterns (e.g., elements in semiconductor devices). In order to meet this demand, light sources configured to emit shorter wavelengths of light have been used in lithography processes. For example, light with wavelengths of about 436 nm ("g-line"), 365 nm ("i-line"), 248 nm (e.g., KrF lasers), and 193 nm (e.g., ArF lasers) have been used as light sources in lithography processes. Recently, it has been proposed to use extreme ultraviolet (EUV) light with a wavelength of about 13.5 nm as a light source for EUV lithography.

[0005] Because most of EUV light is absorbed by refractive optical materials, reflective optics are used instead of refractive optics in EUV lithography. Summary of the invention

[0006] Example embodiments of the inventive concepts provide a phase-shift mask for an extreme ultraviolet lithography process and having an improved contrast property.

[0007] Example embodiments of the inventive concepts provide a phase-shift mask capable of realizing a high-resolution image in an extreme ultraviolet lithography process.

[0008] According to some embodiments of the present invention, a phase shift mask for an extreme ultraviolet lithography process may include a substrate, a reflective layer located on the substrate, a cover layer located on the reflective layer, and a phase shift pattern located on the cover layer. Each of the phase shift patterns may include a lower absorption pattern located on the cover layer and an upper absorption pattern located on the lower absorption pattern. The refractive index of the upper absorption pattern may be higher than the refractive index of the lower absorption pattern, and the thickness of the upper absorption pattern may be less than the thickness of the lower absorption pattern. The cover layer, the lower absorption pattern, and the upper absorption pattern may be stacked sequentially on the substrate.

[0009] According to some embodiments of the present invention, a phase-shift mask for an extreme ultraviolet lithography process may include a substrate, a reflective layer located on the substrate, a covering layer located on the reflective layer, a buffer pattern located on the covering layer, and phase-shift patterns located on the buffer patterns, respectively. Each of the phase-shift patterns may include an upper absorption pattern located on a corresponding buffer pattern among the buffer patterns and a lower absorption pattern located between the corresponding buffer pattern among the buffer patterns and the upper absorption pattern. The lower absorption pattern and the covering layer may contain the same metal element. The refractive index of the upper absorption pattern may be higher than the refractive index of the lower absorption pattern. The thickness of the upper absorption pattern may be less than the thickness of the lower absorption pattern.

[0010] According to some embodiments of the present inventive concept, a phase shift mask for an extreme ultraviolet lithography process may include a substrate, a reflective layer on the substrate, a cover layer on the reflective layer, and a phase shift pattern on the cover layer. Each of the phase shift patterns may include a lower absorption pattern on the cover layer and an upper absorption pattern on the lower absorption pattern. The lower absorption pattern may contain ruthenium (Ru), and the upper absorption pattern may contain tantalum (Ta). The thickness of the upper absorption pattern may be less than the thickness of the lower absorption pattern. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Example embodiments will be more clearly understood from the following brief description taken in conjunction with the accompanying drawings, which illustrate non-limiting example embodiments described herein.

[0012] Figure 1 is a conceptual diagram illustrating an extreme ultraviolet (EUV) lithography system using a phase-shift mask according to some embodiments of the inventive concept.

[0013] Figure 2 is a top view schematically illustrating a phase-shift mask according to some embodiments of the inventive concept.

[0014] Figure 3 is a cross-sectional view schematically illustrating a phase-shift mask according to some embodiments of the inventive concept.

[0015] Figure 4 It is shown Figure 3 A magnified view of a portion of the phase-shift mask.

[0016] Figure 5 is a graph illustrating an amount of phase shift of incident light with respect to a thickness of a phase shift pattern of a phase shift mask according to some embodiments of the inventive concept.

[0017] Figure 6 and Figure 72 are graphs each showing an optical density (OD) property with respect to a thickness of an upper absorption pattern of a phase shift mask according to some embodiments of the present invention.

[0018] Figure 8 is a graph showing a Normalized Image Log Slope (NISL) property of a phase shift mask according to some embodiments of the inventive concept with respect to the thickness of a lower absorption pattern.

[0019] Figures 9 to 12 is a cross-sectional view illustrating a method of manufacturing a phase-shift mask according to some embodiments of the inventive concept. DETAILED DESCRIPTION

[0020] Example embodiments of the inventive concepts will now be described more fully with reference to the accompanying drawings, in which example embodiments are shown.

[0021] Figure 1 is a conceptual diagram illustrating an extreme ultraviolet (EUV) lithography system using a phase-shift mask according to some embodiments of the inventive concept.

[0022] Reference Figure 1 The EUV lithography system 1000 may include a light source unit 10 , a condenser unit 20 , a projection unit 40 , and a control unit 90 .

[0023] The light source unit 10 may generate extreme ultraviolet light 11 (e.g., having a wavelength of about 13.5 nm). The condenser unit 20 may guide the extreme ultraviolet light 11 generated by the light source unit 10 so that the extreme ultraviolet light 11 is incident on the phase-shift mask 500. The condenser unit 20 may include a condenser optical device 22 (e.g., a lens and / or a mirror). The condenser optical device 22 may converge and reflect the extreme ultraviolet light 11 to guide the extreme ultraviolet light 11 to the phase-shift mask 500. The extreme ultraviolet light 11 may be obliquely incident on the phase-shift mask 500 through the condenser unit 20.

[0024] The phase shift mask 500 may be disposed on the mask stage 32, and the mask stage 32 may be configured to move the phase shift mask 500. The light source unit 10 and the mask stage 32 may be controlled by the control unit 90.

[0025] The extreme ultraviolet light 11 incident on the phase shift mask 500 may be reflected by the phase shift mask 500 and then may be incident on the projection unit 40. The projection unit 40 may be configured to project the mask pattern image of the phase shift mask 500 onto the wafer 50. The projection unit 40 may include a projection optical device 42 (e.g., a lens and / or a mirror). The projection optical device 42 may be configured to project the mask pattern image of the phase shift mask 500 onto the wafer 50 in a reduction projection manner (e.g., reduction 4 times, 6 times, or 8 times) using the extreme ultraviolet light 11 reflected by the phase shift mask 500. Since the extreme ultraviolet light 11 is irradiated onto the wafer 50 through the projection unit 40, a pattern corresponding to the mask pattern image of the phase shift mask 500 may be printed on the wafer 50. The wafer 50 may be loaded on the wafer stage 52, and the wafer stage 52 may be configured to move the wafer 50 (e.g., place a desired area of ​​the wafer 50 at an exposure area). As used herein, the term "pattern" refers to a portion of a layer or stacked layers formed on a substrate (e.g., a wafer) by a patterning process that may include a photolithography process and / or an etching process. In addition, the term "and / or" as used herein includes any and all combinations of one or more associated listed items.

[0026] Figure 2 is a top view schematically illustrating a phase shift mask according to some embodiments of the inventive concept, and Figure 3 is a cross-sectional view schematically illustrating a phase-shift mask according to some embodiments of the inventive concept. Figure 4 It is shown Figure 3 A magnified view of a portion of the phase-shift mask.

[0027] Reference Figure 2 and Figure 3 , the phase-shift mask 500 may include a substrate 100, a reflective layer 120, a capping layer 130, a buffer pattern 140, a phase-shift pattern 150, and a lower conductive layer 110. The phase-shift mask 500 may be a reflective phase-shift mask.

[0028] The substrate 100 may be formed of or include a material having a low thermal expansion coefficient. As an example, the substrate 100 may be formed of or include glass or silicon (Si). The substrate 100 may include a pattern area PA and a black border area BA surrounding the pattern area PA, in which a pattern to be transcribed onto a wafer is disposed. The pattern area PA may include a main pattern area 102 and a sub-pattern area 104. The main pattern area 102 may be a main pattern for transcribe a main pattern constituting an integrated circuit onto a wafer (e.g., Figure 1 The sub-pattern area 104 may be an area on a chip area of ​​the wafer 50), and the sub-pattern area 104 may be an area for transcribing an auxiliary pattern to the wafer (eg, Figure 1 The black border area BA may be adjacent to the pattern area PA. For example, when viewed in a top view, the black border area BA may be configured to surround or enclose (eg, partially surround) the pattern area PA. Figure 2 As shown, the black border area BA may completely surround the pattern area PA in a top view. Although not shown, a plurality of alignment and / or identification elements may be provided on the black border area BA. Figure 1 Alignment and / or identification marks of the phase-shift mask 500 in the lithography system 1000 .

[0029] The reflective layer 120 may be disposed on the first surface 100a of the substrate 100. The reflective layer 120 may be disposed on the pattern area PA and may extend onto the black boundary area BA. The reflective layer 120 may reflect light (eg, Figure 1 Extreme ultraviolet light 11). The reflective layer 120 may be configured to function as a Bragg reflector. As an example, the reflective layer 120 may include a multilayer structure in which low refractive index layers 122 and high refractive index layers 124 are alternately and repeatedly stacked. As an example, the number of low refractive index layers 122 and high refractive index layers 124 stacked in the reflective layer 120 may be about 40 to about 60. The low refractive index layer 122 may be formed of, for example, molybdenum (Mo) or include, for example, molybdenum (Mo), and the high refractive index layer 124 may be formed of, for example, silicon (Si) or include, for example, silicon (Si). In some embodiments, the lowest low refractive index layer in the low refractive index layer 122 may be disposed at the lowest layer of the reflective layer 120, and the highest high refractive index layer in the high refractive index layer 124 may be disposed at the highest layer of the reflective layer 120. The layer of the reflective layer 120 closest to the substrate 100 may be one of the low refractive index layers 122 , and the layer of the reflective layer 120 farthest from the substrate 100 may be one of the high refractive index layers 124 .

[0030] In some embodiments, the reflective layer 120 may have a multilayer structure S1 located on the pattern area PA, in which the low refractive index layer 122 and the high refractive index layer 124 are alternately stacked, and a mixed structure S2 located on the black boundary area BA. In this case, the light to be incident on the black boundary area BA (for example, Figure 1 The reflectivity of extreme ultraviolet light 11).

[0031] The cover layer 130 may be disposed on the first surface 100a of the substrate 100 and on the reflective layer 120. The reflective layer 120 may be interposed between the cover layer 130 and the substrate 100. The cover layer 130 may be disposed on the pattern area PA and may extend onto the black boundary area BA. The cover layer 130 may protect the reflective layer 120 and may reduce or prevent surface oxidation of the reflective layer 120. The cover layer 130 may be formed of a metal element (e.g., ruthenium (Ru)) or include a metal element (e.g., ruthenium (Ru)).

[0032] The phase shift pattern 150 may be disposed on the first surface 100a of the substrate 100 and on the cover layer 130. The cover layer 130 may be interposed between the phase shift pattern 150 and the reflective layer 120. The phase shift pattern 150 may be disposed on the pattern area PA and the black boundary area BA, and an opening 150P between the phase shift patterns 150 may be provided to expose a top surface of the cover layer 130.

[0033] The buffer pattern 140 may be disposed on the first surface 100a of the substrate 100 and between the phase-shift pattern 150 and the cover layer 130. Each buffer pattern 140 may be interposed between each phase-shift pattern 150 and the cover layer 130. The opening 150P may extend into a region between the buffer patterns 140 to expose a top surface of the cover layer 130. In some embodiments, the buffer pattern 140 (e.g., a lower surface of the buffer pattern 140) may directly contact the cover layer 130 (e.g., an upper surface of the cover layer 130), such as Figure 3 shown.

[0034] Each phase shift pattern 150 may include a lower absorption pattern 152 and an upper absorption pattern 154 located on the lower absorption pattern 152. The lower absorption pattern 152 may be disposed between each buffer pattern 140 and the upper absorption pattern. In some embodiments, the lower absorption pattern 152 may directly contact both the upper absorption pattern 154 and the buffer pattern 140, such as Figure 3As shown. The upper absorption pattern 154 may be formed of a material having a higher refractive index (n) than the lower absorption pattern 152 or include a material having a higher refractive index (n) than the lower absorption pattern 152. In other words, the refractive index of the upper absorption pattern 154 may be greater than the refractive index of the lower absorption pattern 154. In addition, the upper absorption pattern 154 may be formed of a material having an extinction coefficient (k) higher than the extinction coefficient (k) of the lower absorption pattern 152 or include a material having an extinction coefficient (k) higher than the extinction coefficient (k) of the lower absorption pattern 152. In other words, the extinction coefficient of the upper absorption pattern 154 may be greater than the extinction coefficient of the lower absorption pattern 152. The upper absorption pattern 154 may be formed of or include a tantalum alloy and / or tantalum nitride. As an example, the upper absorption pattern 154 may be formed of or include TaN, TaBN and / or TaSi. The lower absorption pattern 152 may be formed of or include ruthenium (Ru). As an example, the lower absorption pattern 152 may be formed of or contain ruthenium, a ruthenium alloy, ruthenium oxide, ruthenium nitride, and / or ruthenium oxynitride.

[0035] The upper absorption pattern 154 and the lower absorption pattern 152 may each have a thickness measured in a direction perpendicular to the first surface 100a of the substrate 100. The thickness 154T of the upper absorption pattern 154 may be smaller than the thickness 152T of the lower absorption pattern 152.

[0036] The capping layer 130 may be formed of or include the same metal element as the lower absorption pattern 152 (e.g., ruthenium (Ru)), and the buffer pattern 140 may be formed of or include a material different from the capping layer 130 and the lower absorption pattern 152. The buffer pattern 140 may include a material having an etching selectivity relative to the capping layer 130 and the lower absorption pattern 152. The buffer pattern 140 may be formed of or include, for example, silicon, silicon oxide, silicon nitride, silicon oxynitride, tantalum oxide, and / or tantalum oxynitride. In some embodiments, the buffer pattern 140 may be formed of or include SiN, SiO, SiON, TaO, TaON, TaBO, and / or TaBON. Each buffer pattern 140 may have a thickness 140T measured in a direction perpendicular to the first surface 100 a of the substrate 100 , and the thickness 140T of each buffer pattern 140 may be smaller than a thickness 152T of the lower absorption pattern 152 .

[0037] The lower conductive layer 110 may be disposed on a second surface 100b of the substrate 100 opposite to the first surface 100a of the substrate 100. The lower conductive layer 110 may be spaced apart from the reflective layer 120, with the substrate 100 interposed therebetween. The lower conductive layer 110 may be formed of or include a conductive material (e.g., CrN).

[0038] Reference Figure 3 and Figure 4 , the phase shift pattern 150 may absorb a portion of the extreme ultraviolet light IL1 incident to the first surface 100a of the substrate 100. Therefore, the reflectivity of the extreme ultraviolet light IL1 incident to the phase shift pattern 150 may be lower than the reflectivity of the extreme ultraviolet light IL2 incident to the opening 150P. The reflectivity of the extreme ultraviolet light IL1 incident to the phase shift pattern 150 may depend on the extinction coefficient (k) of the material constituting the phase shift pattern 150 and the thickness of the phase shift pattern 150. For example, the smaller the extinction coefficient (k) of the material constituting the phase shift pattern 150 and the smaller the thickness of the phase shift pattern 150, the higher the reflectivity of the extreme ultraviolet light IL1 incident to the phase shift pattern 150.

[0039] The phase shift pattern 150 may be configured to cause a phase shift of the extreme ultraviolet light RL1 that passes through the phase shift pattern 150 and is reflected by the reflective layer 120. Therefore, the phase of the extreme ultraviolet light RL1 that passes through the phase shift pattern 150 and is reflected by the reflective layer 120 may be different from the phase of the extreme ultraviolet light RL2 that passes through the opening 150P and is reflected by the reflective layer 120. The amount of phase shift of the extreme ultraviolet light RL1 that passes through the phase shift pattern 150 and is reflected by the reflective layer 120 may be changed according to the refractive index (n) of the material constituting the phase shift pattern 150 and the thickness of the phase shift pattern 150. As an example, the smaller the refractive index of the material constituting the phase shift pattern 150 and the greater the thickness of the phase shift pattern 150, the greater the amount of phase shift of the extreme ultraviolet light RL1 that passes through the phase shift pattern 150 and is reflected by the reflective layer 120.

[0040] The smaller the refractive index (n) of the material constituting the phase shift pattern 150, the greater the amount of extreme ultraviolet light IL1 incident to the phase shift pattern 150 and reflected from the surface of the phase shift pattern 150. In this case, the phase shift mask 500 may have degraded mask contrast properties.

[0041] According to some embodiments of the inventive concept, the refractive index (n) of the lower absorption pattern 152 may be smaller than the refractive index (n) of the upper absorption pattern 154, and the thickness 152T of the lower absorption pattern 152 may be greater than the thickness 154T of the upper absorption pattern 154. Therefore, the phase shift amount of the extreme ultraviolet light RL1 that passes through the phase shift pattern 150 and is reflected by the reflective layer 120 may be increased, and in this case, a high-resolution image may be easily realized using the phase shift mask 500.

[0042] In addition, the refractive index (n) of the upper absorption pattern 154 may be greater than the refractive index (n) of the lower absorption pattern 152, and thus, the amount of extreme ultraviolet light IL1 incident to the phase shift pattern 150 and reflected from the surface of the phase shift pattern 150 may be reduced. In some embodiments, the extinction coefficient (k) of the upper absorption pattern 154 may be greater than the extinction coefficient (k) of the lower absorption pattern 152, and thus, the reflectivity of the extreme ultraviolet light IL1 incident to the phase shift pattern 150 may be reduced. In this case, the mask contrast property of the phase shift mask 500 may be improved.

[0043] Figure 5 is a graph illustrating an amount of phase shift of incident light with respect to a thickness of a phase shift pattern of a phase shift mask according to some embodiments of the inventive concept.

[0044] Reference Figure 4 and Figure 5 , the phase shift pattern 150 may be configured to change the extreme ultraviolet light RL1 passing through the phase shift pattern 150 and reflected by the reflective layer 120 to have a phase difference of about 180° to about 250° relative to the extreme ultraviolet light RL2 passing through the opening 150P and reflected by the reflective layer 120 (hereinafter, referred to as a phase difference condition). The thickness 154T of the upper absorption pattern 154 and the thickness 152T of the lower absorption pattern 152 may be adjusted to satisfy the phase difference condition. As an example, the thickness 154T of the upper absorption pattern 154 may be in a range of about 8 nm to about 35 nm, and the thickness 152T of the lower absorption pattern 152 may be in a range of about 10 nm to about 40 nm.

[0045] Because the phase shift pattern 150 is configured to satisfy the phase difference condition, the extreme ultraviolet light RL1 passing through the phase shift pattern 150 and reflected by the reflective layer 120 may destructively interfere with the extreme ultraviolet light RL2 passing through the opening 150P and reflected by the reflective layer 120. Figure 1 In the case of performing an exposure process using the phase shift mask 500 on the photoresist layer on the wafer 50, the intensity of the extreme ultraviolet light incident on the region of the photoresist layer corresponding to the phase shift pattern 150 can be reduced due to destructive interference between the extreme ultraviolet light RL1 and the extreme ultraviolet light RL2. In other words, the image projected on the photoresist layer can have a high normalized image logarithmic slope (NISL), and this can easily realize a high-resolution image on the photoresist layer.

[0046] Figure 6 and Figure 7 1 and 2 are graphs showing optical density (OD) properties relative to an upper absorption pattern of a phase shift mask (eg, Figure 4 A graph of the thickness of the upper absorption pattern 154) in FIG.

[0047] Reference Figure 4 , Figure 6 and Figure 7 , the mask contrast property of the phase-shift mask 500 can be evaluated by the following equation 1:

[0048] [Formula 1]

[0049] OD=-log(Ra / Rb)

[0050] Here, Ra is the reflectivity of the extreme ultraviolet light IL1 incident to the phase shift pattern 150 , Rb is the reflectivity of the extreme ultraviolet light IL2 incident to the opening 150P, and OD is the optical density indicating the degree of light blocking property.

[0051] In some embodiments, the black border area BA is required to have an optical density (OD) of 2.8 or higher. Hereinafter, this condition (OD ≥ 2.8) will be referred to as an optical density condition.

[0052] Figure 6 The optical density (OD) property and the reflectivity ratio (Ra / Rb) property of the black boundary area BA in relation to the thickness 154T of the upper absorption pattern 154 are shown when the thickness 152T of the lower absorption pattern 152 is 32 nm. Figure 6 It is shown that when the thickness 152T of the lower absorption pattern 152 is 32 nm and the thickness 154T of the upper absorption pattern 154 has values ​​close to 9.5 nm, 16.5 nm, 24 nm, 31 nm, and 38 nm, the optical density (OD) condition of the black boundary area BA (ie, OD ≥ 2.8) can be satisfied.

[0053] Figure 7 It is shown that when the thickness 152T of the lower absorption pattern 152 is 30 nm, the optical density (OD) and reflectivity ratio (Ra / Rb) properties of the black boundary area BA relative to the thickness 154T of the upper absorption pattern 154 . Figure 7 It is shown that when the thickness 152T of the lower absorption pattern 152 is 30 nm and the thickness 154T of the upper absorption pattern 154 has values ​​close to 9.5 nm, 16.5 nm, 24 nm, 31 nm, and 38 nm, the optical density (OD) condition (OD ≥ 2.8) of the black boundary area BA can be satisfied.

[0054] According to some embodiments of the present inventive concept, the thickness 154T of the upper absorption pattern 154 may be adjusted to satisfy the phase difference condition (about 180° to about 250°) and the optical density condition (OD ≥ 2.8) of the black boundary area BA. As an example, the thickness 154T of the upper absorption pattern 154 may be adjusted to have a value satisfying the optical density condition in the range of about 8 nm to about 35 nm. Since the phase shift pattern 150 is configured to satisfy the optical density condition, the mask contrast property of the phase shift mask 500 may be improved.

[0055] Figure 8 is a graph showing the normalized image logarithmic slope (NISL) property of a phase shift mask according to some embodiments of the inventive concept with respect to the thickness of a lower absorption pattern. Figure 8 , i) the solid line represents the change in NISL properties caused by the change in the thickness 152T of the lower absorption pattern 152 when the thickness 154T of the upper absorption pattern 154 is 9.5 nm, and ii) the dotted line represents the change in NISL properties caused by the change in the thickness 152T of the lower absorption pattern 152 when the upper absorption pattern 154 is not set.

[0056] Reference Figure 4 and Figure 8 , the refractive index (n) of the lower absorption pattern 152 may be less than the refractive index (n) of the upper absorption pattern 154, and the thickness 152T of the lower absorption pattern 152 may be greater than the thickness 154T of the upper absorption pattern 154. In other words, the lower absorption pattern 152 having a relatively low refractive index (n) may be provided to be thicker than the upper absorption pattern 154 having a relatively high refractive index (n).

[0057] According to some embodiments of the inventive concept, the thickness 152T of the lower absorption pattern 152 may be adjusted to satisfy the phase difference condition (about 180° to about 250°) and change the phase shift mask 500 to have the desired NISL properties. As an example, the thickness 152T of the lower absorption pattern 152 may be in the range of about 10 nm to about 40 nm. Figure 8 , when the thickness 152T of the lower absorption pattern 152 is less than or equal to about 40 nm, the phase-shift mask 500 according to some embodiments of the inventive concept may have an improved (or higher) or equivalent NILS property compared to the NILS property of a phase-shift mask in which the upper absorption pattern 154 is not provided on the lower absorption pattern 152. Since the phase-shift pattern 150 is configured to satisfy the desired (higher) NILS property, a phase-shift mask 500 capable of easily realizing a high-resolution image may be provided.

[0058] Figures 9 to 12 2 is a cross-sectional view showing a method of manufacturing a phase shift mask according to some embodiments of the present invention. Figures 2 to 4 Elements of the described phase-shift mask may be identified by the same reference numerals without repeating a repeated description thereof.

[0059] Reference Fig. 9 , a substrate 100 may be provided. The substrate 100 may be formed of or include a material having a low thermal expansion coefficient. As an example, the substrate 100 may be formed of or include glass or silicon. The substrate 100 may include a reference Figure 1 and Figure 2 Described is the pattern area PA and the black border area BA.

[0060] A lower conductive layer 110 may be formed on the second surface 100b of the substrate 100. The lower conductive layer 110 may include, for example, a CrN layer formed by a sputtering deposition process.

[0061] A reflective layer 120 may be formed on the first surface 100a of the substrate 100. The formation of the reflective layer 120 may include alternately and repeatedly forming a low refractive index layer 122 and a high refractive index layer 124 on the first surface 100a of the substrate 100. The reflective layer 120 may be formed to have 40-60 low refractive index layers 122 and 40-60 high refractive index layers 124, which are alternately stacked by, for example, a sputtering deposition process. In some embodiments, the formation of the reflective layer 120 may include performing a laser annealing process on the black border area BA. In this case, the low refractive index layer 122 and the high refractive index layer 124 on the black border area BA may be mixed with each other by the laser annealing process. Therefore, the reflective layer 120 may have a multilayer structure S1 in which the low refractive index layer 122 and the high refractive index layer 124 are alternately stacked on the pattern area PA, and may have a mixed structure S2 in which the low refractive index layer 122 and the high refractive index layer 124 are mixed with each other on the black border area BA.

[0062] The capping layer 130 may be formed on the reflective layer 120. The capping layer 130 may include, for example, ruthenium, and may be formed through a sputtering deposition process.

[0063] A buffer layer 140L may be formed on the capping layer 130. The buffer layer 140L may be formed of or include a material having an etching selectivity with respect to the capping layer 130. In addition, the buffer layer 140L may be formed of or include a material having an etching selectivity with respect to a lower absorption layer 152L to be described below. For example, the buffer layer 140L may be formed of or include silicon, silicon oxide, silicon nitride, silicon oxynitride, tantalum oxide, and / or tantalum oxynitride. The buffer layer 140L may be formed by, for example, a chemical vapor deposition process, a sputtering deposition process, or the like.

[0064] A lower absorption layer 152L may be formed on the buffer layer 140L. The lower absorption layer 152L may be formed of or include the same metal element (e.g., ruthenium) as the capping layer 130. The lower absorption layer 152L may be formed of or include, for example, ruthenium, a ruthenium alloy, ruthenium oxide, ruthenium nitride, and / or ruthenium oxynitride. The lower absorption layer 152L may be formed by, for example, a sputtering deposition process. The lower absorption layer 152L may be formed to have a thickness 152T greater than the thickness 140T of the buffer layer 140L.

[0065] The upper absorption layer 154L may be formed on the lower absorption layer 152L. The upper absorption layer 154L may be formed of a material having a higher refractive index than the lower absorption layer 152L. In addition, the upper absorption layer 154L may be formed of a material having an extinction coefficient greater than the extinction coefficient of the lower absorption layer 152L. As an example, the upper absorption layer 154L may be formed of or include a tantalum alloy and / or tantalum nitride. The upper absorption layer 154L may be formed by, for example, a sputtering deposition process. The upper absorption layer 154L may be formed to have a thickness 154T that is less than a thickness 152T of the lower absorption layer 152L. According to some embodiments, the thickness 154T of the upper absorption layer 154L and the thickness 152T of the lower absorption layer 152L may be adjusted to meet a reference Figures 5 to 8 The conditions described (e.g., phase difference conditions, optical density (OD), and NILS). As an example, the thickness 154T of the upper absorption layer 154L may be in the range of about 8 nm to about 35 nm, and the thickness 152T of the lower absorption layer 152L may be in the range of about 10 nm to about 40 nm.

[0066] A hard mask layer 160L may be formed on the upper absorption layer 154L. The hard mask layer 160L may be formed of or include a material having an etching selectivity with respect to the upper absorption layer 154L and the lower absorption layer 152L. The hard mask layer 160L may be formed of or include, for example, silicon, silicon oxide, silicon nitride, silicon oxynitride, tantalum oxide, and / or tantalum oxynitride. In some embodiments, the hard mask layer 160L may be formed of or include the same material as the buffer layer 140L. The hard mask layer 160L may be formed by, for example, a chemical vapor deposition process, a sputtering deposition process, or the like.

[0067] A photoresist pattern 170 may be formed on the hard mask layer 160L. The photoresist pattern 170 may define the shape and location of a region in which a phase shift pattern to be described below will be formed.

[0068] Reference Fig.10 , the hard mask layer 160L may be etched using the photoresist pattern 170 as an etching mask. Thus, the hard mask pattern 160 may be formed on the upper absorption layer 154L. In some embodiments, the formation of the hard mask pattern 160 may include using an etching source (eg, containing SF 6 CF 4 and / or CHF 3 ) to etch the hard mask layer 160L. The term "etching source" as used herein refers to an etchant.

[0069] Reference Fig.11 , the photoresist pattern 170 may be removed. The photoresist pattern 170 may be removed by, for example, ashing and / or stripping processes. The upper absorption layer 154L may be etched using the hard mask pattern 160 as an etching mask. Thus, an upper absorption pattern 154 may be formed on the lower absorption layer 152L. In some embodiments, the formation of the upper absorption pattern 154 may include using an etching source (e.g., a Cl 2 ) to etch the upper absorption layer 154L.

[0070] Reference Fig.12 , the lower absorption layer 152L may be etched using the hard mask pattern 160 as an etching mask. Thus, a lower absorption pattern 152 may be formed on the buffer layer 140L. The lower absorption pattern 152 and the upper absorption pattern 154 may constitute a phase shift pattern 150. Each phase shift pattern 150 may include a pair of lower absorption patterns 152 and upper absorption patterns 154 sequentially stacked on the buffer layer 140L. In some embodiments, the formation of the lower absorption pattern 152 may include using an etching source (e.g., a Cl 2 and O 2) to etch the lower absorption layer 152L. During the formation of the lower absorption layer 152L, the buffer layer 140L may be used as an etch stop layer. Therefore, the capping layer 130 may be protected during the etching of the lower absorption layer 152L.

[0071] Return to reference Figure 3 , the buffer layer 140L may be etched using the phase shift pattern 150 as an etching mask. Thus, the buffer pattern 140 may be formed on the capping layer 130. Each buffer pattern 140 may be interposed between each phase shift pattern 150 and the capping layer 130. In some embodiments, the formation of the buffer pattern 140 may include using an etching source (e.g., containing SF 6 CF 4 and / or CHF 3 ) is used to etch the buffer layer 140L. The hard mask pattern 160 may be removed during the etching of the buffer layer 140L.

[0072] According to some embodiments of the present inventive concept, the phase shift pattern may include a lower absorption pattern and an upper absorption pattern. The upper absorption pattern may be disposed on the lower absorption pattern and may have a higher refractive index than that of the lower absorption pattern, and in this case, the amount of extreme ultraviolet light incident on the phase shift pattern and reflected from the surface of the phase shift pattern may be reduced. This may improve the mask contrast properties of the phase shift mask.

[0073] In addition, the lower absorption pattern having a relatively low refractive index can be thicker than the upper absorption pattern, and thus the phase shift of the extreme ultraviolet light reflected by the phase shift pattern can be increased. Therefore, a high-resolution image can be easily achieved using the phase shift mask.

[0074] Therefore, a phase-shift mask having improved mask contrast properties and enabling high-resolution images can be used in an EUV lithography process.

[0075] While example embodiments of the inventive concepts have been particularly shown and described, it will be understood by those skilled in the art that changes in form and details may be made therein without departing from the scope of the appended claims.

[0076] The subject matter disclosed above should be considered illustrative rather than restrictive, and the appended claims are intended to cover all such modifications, improvements and other embodiments that fall within the true spirit and scope of the inventive concept. Therefore, the scope of the appended claims will not be restricted or limited by the foregoing detailed description.

Claims

1. A phase-shift mask for extreme ultraviolet lithography, comprising: substrate; a reflective layer, located on the substrate; a covering layer, located on the reflecting layer; and a phase shift pattern, located on the cover layer, Wherein, each of the phase shift patterns comprises: a lower absorption pattern located on the cover layer; and an upper absorption pattern, located on the lower absorption pattern, Wherein, the refractive index of the upper absorption pattern is higher than the refractive index of the lower absorption pattern, and, The thickness of the upper absorption pattern is smaller than the thickness of the lower absorption pattern, The substrate includes a pattern area and a black border area surrounding the pattern area, and The reflective layer has a multilayer structure located on the pattern area and a mixed structure located on the black boundary area, the multilayer structure includes a first portion of high refractive index layers and a first portion of low refractive index layers alternately stacked, and the mixed structure includes a second portion of high refractive index layers and a second portion of low refractive index layers mixed with each other.

2. The phase-shift mask according to claim 1, wherein: An extinction coefficient of the upper absorption pattern is greater than an extinction coefficient of the lower absorption pattern.

3. The phase-shift mask according to claim 2, further comprising an opening located between the two phase-shift patterns and exposing the cover layer, in, The phase shift pattern is configured to change a first portion of the extreme ultraviolet light to have a phase difference of 180° to 250° relative to a second portion of the extreme ultraviolet light, the first portion of the extreme ultraviolet light passing through one of the phase shift patterns and reflected from the reflective layer, and the second portion of the extreme ultraviolet light passing through the opening and reflected from the reflective layer.

4. The phase-shift mask according to claim 2, wherein: The lower absorption pattern includes ruthenium.

5. The phase-shift mask according to claim 4, wherein: The upper absorption pattern includes tantalum alloy and / or tantalum nitride.

6. The phase-shift mask according to claim 1, wherein: The thickness of the upper absorption pattern is in the range of 8 nm to 35 nm.

7. The phase-shift mask according to claim 6, wherein: The thickness of the lower absorption pattern is in the range of 10 nm to 40 nm.

8. The phase-shift mask according to claim 1, further comprising a buffer pattern located on the cover layer, in, Each of the buffer patterns is located between the cover layer and the corresponding phase shift pattern, The lower absorption pattern and the cover layer contain the same metal element, and Each of the buffer patterns includes a material different from that of the lower absorption pattern and the cover layer.

9. A phase-shift mask for extreme ultraviolet lithography, comprising: substrate; a reflective layer, located on the substrate; a covering layer, located on the reflecting layer; a buffer pattern, located on the cover layer; and phase shift patterns, respectively located on the buffer patterns, Wherein, each of the phase shift patterns comprises: an upper absorption pattern located on a corresponding one of the buffer patterns; and a lower absorption pattern, located between the corresponding buffer pattern in the buffer pattern and the upper absorption pattern, wherein the lower absorption pattern and the cover layer contain the same metal element, The refractive index of the upper absorption pattern is higher than the refractive index of the lower absorption pattern, and The thickness of the upper absorption pattern is smaller than the thickness of the lower absorption pattern, The substrate includes a pattern area and a black border area surrounding the pattern area, and The reflective layer has a multilayer structure located on the pattern area and a mixed structure located on the black boundary area, the multilayer structure includes a first portion of high refractive index layers and a first portion of low refractive index layers alternately stacked, and the mixed structure includes a second portion of high refractive index layers and a second portion of low refractive index layers mixed with each other.

10. The phase-shift mask according to claim 9, wherein: An extinction coefficient of the upper absorption pattern is greater than an extinction coefficient of the lower absorption pattern.

11. The phase-shift mask according to claim 9, wherein: The lower absorption pattern and the capping layer include ruthenium.

12. The phase-shift mask according to claim 11, wherein: The upper absorption pattern includes tantalum alloy and / or tantalum nitride.

13. The phase-shift mask according to claim 11, wherein: The buffer pattern includes a material different from that of the lower absorption pattern and the capping layer.

14. The phase-shift mask according to claim 13, wherein: The buffer pattern includes silicon, silicon oxide, silicon nitride, silicon oxynitride, tantalum oxide and / or tantalum oxynitride.

15. A phase-shift mask for extreme ultraviolet lithography, comprising: substrate; a reflective layer, located on the substrate; a covering layer, located on the reflecting layer; and a phase shift pattern, located on the cover layer, Wherein, each of the phase shift patterns comprises: a lower absorption pattern located on the cover layer; and an upper absorption pattern, located on the lower absorption pattern, wherein the lower absorption pattern comprises ruthenium, The upper absorption pattern comprises tantalum, and The thickness of the upper absorption pattern is smaller than the thickness of the lower absorption pattern, The substrate includes a pattern area and a black border area surrounding the pattern area, and The reflective layer has a multilayer structure located on the pattern area and a mixed structure located on the black boundary area, the multilayer structure includes a first portion of high refractive index layers and a first portion of low refractive index layers alternately stacked, and the mixed structure includes a second portion of high refractive index layers and a second portion of low refractive index layers mixed with each other.

16. The phase-shift mask according to claim 15, further comprising a buffer pattern on the cover layer, in, Each of the buffer patterns is located between the cover layer and the corresponding phase shift pattern, The capping layer comprises ruthenium, and Each of the buffer patterns includes a material different from that of the lower absorption pattern and the cover layer.

17. The phase-shift mask according to claim 16, wherein: Each of the buffer patterns includes silicon, silicon oxide, silicon nitride, silicon oxynitride, tantalum oxide and / or tantalum oxynitride.

18. The phase-shift mask according to claim 15, wherein: The lower absorption pattern includes a ruthenium alloy, ruthenium oxide, ruthenium nitride and / or ruthenium oxynitride.

19. The phase-shift mask according to claim 15, wherein: The upper absorption pattern includes tantalum alloy and / or tantalum nitride.

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