Phase shift mask for extreme ultraviolet lithography and method of forming a semiconductor device using the same

Abstract

The present invention provides a phase inversion mask for extreme ultraviolet lithography and a method for manufacturing a semiconductor device using the same. The phase inversion mask for extreme ultraviolet lithography comprises: a substrate; a reflective layer on the substrate; a capping film disposed on the reflective layer; a buffer pattern disposed on the capping film and providing an opening that exposes the surface of the capping film; and an absorber pattern on the buffer pattern, wherein the buffer pattern comprises a material having etch selectivity with respect to the absorber pattern and the capping film, the refractive index of the absorber pattern is smaller than the refractive index of the buffer pattern, and the thickness of the absorber pattern is greater than the thickness of the buffer pattern.

Description

Technology Field

[0001] The present invention relates to a phase inversion mask for extreme ultraviolet lithography and a method for manufacturing a semiconductor device using the same. Background Technology

[0002] As the size and design rules of semiconductor devices gradually shrink, there is a demand for technology to form patterns of even smaller sizes. To meet these technical demands, the wavelength of light sources used in lithography processes is becoming shorter. For example, light sources used in lithography processes are becoming shorter, such as g-line (436 nm), i-line (365 nm), KrF laser (248 nm), and ArF laser (193 nm). Recently, extreme ultraviolet lithography using extreme ultraviolet light with a wavelength of 13.5 nm as a light source has been proposed.

[0003] Because extreme ultraviolet light is absorbed by most refractive optical materials, extreme ultraviolet lithography generally uses a reflective optical system rather than a refractive optical system. The problem to be solved

[0004] The technical problem that the present invention aims to solve is to provide a phase inversion mask for extreme ultraviolet lithography capable of realizing high-resolution images.

[0005] Another technical problem that the present invention aims to solve is to provide a method for manufacturing a semiconductor device that can improve productivity.

[0006] The problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0007] A phase inversion mask for extreme ultraviolet lithography according to the concept of the present invention for achieving the above technical problem comprises: a substrate; a reflective layer on the substrate; a capping film disposed on the reflective layer; a buffer pattern disposed on the capping film and providing an opening that exposes the surface of the capping film; and an absorber pattern on the buffer pattern, wherein the buffer pattern comprises a material having etch selectivity with respect to the absorber pattern and the capping film, the refractive index of the absorber pattern is smaller than the refractive index of the buffer pattern, and the thickness of the absorber pattern is greater than the thickness of the buffer pattern.

[0008] A phase inversion mask for extreme ultraviolet lithography according to one aspect of the present invention comprises: a substrate on a conductive layer; a reflective layer on the substrate; a capping film disposed on the reflective layer; and an absorber pattern disposed on the capping film and providing an opening that exposes the surface of the capping film, wherein the absorber pattern comprises nitrogen and chromium, and the content of nitrogen in the absorber pattern is 5 to 70 at.%.

[0009] A phase inversion mask for extreme ultraviolet lithography according to another aspect of the present invention comprises: a substrate; a reflective layer on the substrate; a capping film disposed on the reflective layer; a buffer pattern disposed on the capping film and providing an opening that exposes the surface of the capping film; and an absorber pattern on the buffer pattern, wherein the buffer pattern comprises a material having etch selectivity with respect to the absorber pattern, and the absorber pattern comprises nitrogen and chromium, and the content of the nitrogen within the absorber pattern varies discontinuously or gradually depending on the distance from the buffer pattern.

[0010] A method for manufacturing a semiconductor device according to the present invention for achieving the above other technical objectives comprises the steps of: sequentially stacking an etching target film and a photoresist film on a wafer; and performing an exposure process on the photoresist film using a phase inversion mask for extreme ultraviolet lithography, wherein the phase inversion mask for extreme ultraviolet lithography comprises: a substrate; a reflective layer on the substrate; a capping film disposed on the reflective layer; a buffer pattern disposed on the capping film and providing an opening that exposes the surface of the capping film; and an absorber pattern on the buffer pattern, wherein the buffer pattern comprises a material having etch selectivity with respect to the absorber pattern and the capping film, the refractive index of the absorber pattern is smaller than the refractive index of the buffer pattern, and the thickness of the absorber pattern is greater than the thickness of the buffer pattern. Effects of the invention

[0011] A phase inversion mask for extreme ultraviolet lithography according to the concept of the present invention can realize high-resolution images by adopting chromium nitride as an absorber pattern. Since the absorber pattern has a lower refractive index and a thicker thickness than the buffer pattern, the degree of phase shift of extreme ultraviolet light can be increased. Accordingly, it may be easy to realize high-resolution images using the phase inversion mask. In addition, if a silicon-containing film is used as the buffer film, a capping film made of ruthenium can be omitted, thereby simplifying the structure and process. Thus, a phase inversion mask for extreme ultraviolet lithography capable of realizing high-resolution images can be provided.

[0012] A method for manufacturing a semiconductor device according to the concept of the present invention can reduce process defects and improve productivity by using the phase inversion mask for extreme ultraviolet lithography.

[0013] A method for manufacturing a phase inversion mask for extreme ultraviolet lithography according to another concept of the present invention can reduce process defects and improve productivity by adopting a buffer and a mask pattern as materials having excellent etching selectivity with respect to an absorber pattern and a capping film. Brief explanation of the drawing

[0014] FIG. 1 is a conceptual diagram showing an extreme ultraviolet lithography apparatus using a phase inversion mask according to some embodiments of the present invention. FIG. 2 is a plan view schematically showing a phase inversion mask according to some embodiments of the present invention. FIG. 3 is a cross-sectional view schematically illustrating a phase inversion mask according to some embodiments of the present invention. FIGS. 4a to 4c show the detailed structure of an absorbent pattern according to embodiments of the present invention. FIG. 5 is a drawing showing a part of a phase inversion mask according to embodiments of the present invention. FIG. 6a is a graph showing NILS values ​​according to the thickness of the absorber pattern of the phase inversion mask according to embodiments of the present invention. FIG. 6b is a graph showing NILS values ​​according to the thickness of the absorber pattern of the phase inversion mask according to embodiments of the present invention. FIG. 6c is a graph showing NILS values ​​according to dose amount in phase inversion masks according to embodiments and comparative examples of the present invention. FIGS. 7a to 7c are cross-sectional views illustrating the processes of manufacturing the phase inversion mask of FIG. 3 according to embodiments of the present invention. FIG. 8 is a cross-sectional view of a phase inversion mask according to embodiments of the present invention. Figure 9 is a cross-sectional view showing the process of manufacturing the phase inversion mask of Figure 8. Specific details for implementing the invention

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0017] FIG. 1 is a conceptual diagram showing an extreme ultraviolet (EUV) lithography apparatus using a phase inversion mask according to some embodiments of the present invention.

[0018] Referring to FIG. 1, an extreme ultraviolet lithography device (1000) may include a light source unit (10, optical source unit), a light collecting unit (20, condenser unit), a projection unit (40, projection unit), and a control unit (90).

[0019] The light source unit (10) can generate extreme ultraviolet rays (for example, light having a wavelength of about 13.5 nm). The light collecting unit (20) can guide the extreme ultraviolet rays (11) generated from the light source unit (10) so that they are irradiated onto the phase inversion mask (500). The light collecting unit (20) may include a condenser optical system (22, condenser optics, for example, a lens and / or a mirror). The condenser optical system (22) can guide the extreme ultraviolet rays (11) to the phase inversion mask (500) by collecting and reflecting the extreme ultraviolet rays (11). The extreme ultraviolet rays (11) may be incident on the phase inversion mask (500) at an angle through the light collecting unit (20).

[0020] The phase inversion mask (500) may be provided on a mask stage (32), and the mask stage (32) may be configured to move the phase inversion mask (500). The light source unit (10) and the mask stage (32) may be controlled by a control unit (90).

[0021] The extreme ultraviolet rays (11) incident on the phase inversion mask (500) may be reflected from the phase inversion mask (500) and incident on the projection unit (40). The projection unit (40) may project the mask pattern image of the phase inversion mask (500) onto a wafer (50). The projection unit (40) may include projection optics (42) (e.g., lenses and / or mirrors). The projection optics (42) may use the extreme ultraviolet rays (11) reflected from the phase inversion mask (500) to reduce the mask pattern image of the phase inversion mask (500) by a predetermined magnification (e.g., 4x, 6x, or 8x) and project it onto the wafer (50). An etching target film (1) and a photoresist film (2) may be stacked sequentially on the wafer (50). As the extreme ultraviolet rays (11) pass through the projection unit (40) and are irradiated onto the wafer (50), patterns corresponding to the mask pattern image of the phase inversion mask (500) can be printed on the photoresist film on the wafer (50). After this exposure process, a photoresist pattern can be formed through a development process. The etching target film (1) can be etched using the photoresist pattern. The wafer (50) can be loaded onto a wafer stage (52), and the wafer stage (52) can be configured to move the wafer (50) to change the exposure area within the wafer (50). The exposure process using the phase inversion mask (500) can be performed in a vacuum.

[0023] FIG. 2 is a plan view schematically illustrating a phase inversion mask according to some embodiments of the present invention. FIG. 3 is a cross-sectional view schematically illustrating a phase inversion mask according to some embodiments of the present invention.

[0024] Referring to FIGS. 2 and 3, the phase inversion mask (500) may include a substrate (100), a reflective layer (120), a capping film (130), buffer patterns (140), absorber patterns (150), and a lower conductive layer (110). The phase inversion mask (500) may be a reflective attenuated phase inversion mask.

[0025] The substrate (100) may include a material having a low coefficient of thermal expansion. For example, the substrate (100) may include glass or silicon (Si). The substrate (100) may include a pattern area (PA) on which patterns to be transferred to a wafer are placed, and a black border area (BA) around the pattern area (PA). The pattern area (PA) may include a main pattern area (102) and a sub-pattern area (104). The main pattern area (102) may be an area for transferring main patterns constituting an integrated circuit onto a chip area of ​​the wafer (50 in FIG. 1), and the sub-pattern area (104) may be an area for transferring auxiliary patterns onto a scribe line area of ​​the wafer (50 in FIG. 1). The black border area (BA) may surround the pattern area (PA) in a planar view. Although not shown, alignment marks for aligning the phase inversion mask (500) and / or identification marks for identifying the phase inversion mask (500) may be placed on the black border area (BA) within the lithography device (1000) of FIG. 1.

[0026] The reflective layer (120) may be disposed on a first surface (100a) of the substrate (100). The reflective layer (120) may be disposed on the pattern area (PA) and may extend over the black border area (BA). The reflective layer (120) may reflect light incident on the reflective layer (120) (for example, the extreme ultraviolet light (11) of FIG. 1). The reflective layer (120) may include a Bragg reflector. For 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. For example, the low-refractive-index layers (122) and the high-refractive-index layers (124) may each be stacked about 40 to about 60 times. The low-refractive-index layers (122) may include, for example, molybdenum (Mo), and the high-refractive-index layers (124) may include, for example, silicon (Si). According to some embodiments, the lowest low-refractive-index layer (122) may be placed at the bottom of the reflective layer (120), and the highest high-refractive-index layer (124) may be placed at the top of the reflective layer (120).

[0027] According to some embodiments, the reflective layer (120) may have a first portion (S1) and a second portion (S2). The first portion (S1) may have a multilayer structure in which the low-refractive-index layers (122) and the high-refractive-index layers (124) are alternately stacked on the pattern area (PA), and the second portion (S2) may have an intermixed structure in which the low-refractive-index layers (122) and the high-refractive-index layers (124) are intermixed on the black border area (BA). The reflectance of light incident on the second portion (S2) of the reflective layer (120) (e.g., the extreme ultraviolet light (11) of FIG. 1) is reduced so that it can function as a black border area.

[0028] The lower conductive layer (110) may be disposed on the second surface (100b) of the substrate (100) facing 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) in between. The lower conductive layer (110) may include a conductive material (e.g., CrN). The lower conductive layer (110) is for the operation of an electrostatic chuck and may be used to mount a phase inversion mask for extreme ultraviolet lithography on a mask stage.

[0029] The capping film (130) may be disposed on the reflective layer (120) on the first surface (100a) of the substrate (100). The reflective layer (120) may be interposed between the capping film (130) and the substrate (100). The capping film (130) may be disposed on the pattern area (PA) and may extend onto the black border area (BA). The capping film (130) may protect the reflective layer (120) and prevent the surface of the reflective layer (120) from oxidizing. The capping film (130) may include a metal (e.g., ruthenium (Ru)).

[0030] The absorber patterns (150) may be disposed on the capping film (130) on the first surface (100a) of the substrate (100). The capping film (130) may be interposed between the absorber patterns (150) and the reflective layer (120). The absorber patterns (150) may be disposed on the pattern area (PA) and the black border area (BA), and openings (150P) between the absorber patterns (150) may expose the upper surface of the capping film (130).

[0031] The buffer patterns (140) may be disposed on the first surface (100a) of the substrate (100) between the absorber patterns (150) and the capping film (130). Each of the buffer patterns (140) may be interposed between each of the absorber patterns (150) and the capping film (130). The openings (150P) may extend between the buffer patterns (140) to expose the upper surface of the capping film (130).

[0032] The buffer patterns (140) may include a material different from the capping film (130) and the lower absorption pattern (152). The buffer patterns (140) may include a material having etch selectivity for the capping film (130) and the lower absorption pattern (152). The buffer patterns (140) may also be referred to as etch prevention patterns. The buffer patterns (140) may include a silicon-containing film, a metal-containing film, a metal nitride, or a metal oxide. The buffer patterns (140) may include at least one selected from Si, SiN, SiO2, SiON, TaBO, TaO, TaON, TaN, TaBN, TiN, Nb, and Ta.

[0033] The upper surface of the absorber pattern (150) may be exposed without being covered by anything. The absorber pattern (150) may also be referred to as a phase inversion pattern. The absorber pattern (150) may contain nitrogen (atoms) and chromium (atoms). The absorber pattern (150) may further contain oxygen (atoms). The absorber pattern (150) may contain at least one of chromium nitride and chromium nitride oxide. The refractive index and absorption coefficient of the absorber pattern (150) may vary depending on the nitrogen content, density, and deposition conditions within the absorber pattern (150). Preferably, the content of nitrogen (atoms) within the absorber pattern (150) may be 5 to 70 at.%. At this time, for extreme ultraviolet rays, the refractive index of the absorber pattern (150) may be 0.925 to 0.935, and the absorption coefficient may be 0.03 to 0.04.

[0034] The nitrogen content within the absorber pattern (150) according to distance from the upper surface of the capping membrane (130) may vary stepwise, discontinuously, gradually, or continuously. The absorber pattern (150) may have a single membrane form having an overall uniform composition including nitrogen and chromium. Alternatively, the absorber pattern (150) may have a multi-layer form with two or more layers having different compositions of nitrogen and chromium. Such a multi-layer structure may be described with reference to FIGS. 4a and 4b below.

[0036] FIGS. 4a to 4c show the detailed structure of an absorbent pattern according to embodiments of the present invention.

[0037] Referring to FIG. 4a, the absorbent pattern (150) may include a first absorbent portion (150a) and a second absorbent portion (150b) above it. The first absorbent portion (150a) and the second absorbent portion (150b) contain nitrogen and chromium. The nitrogen content of the first absorbent portion (150a) may differ from the nitrogen content of the second absorbent portion (150b). For example, the nitrogen content in the first absorbent portion (150a) may be smaller than the nitrogen content in the second absorbent portion (150b).

[0038] Referring to FIG. 4b, the absorber pattern (150) may further include a third absorber portion (150c) on a second absorber portion (150b). The first to third absorber portions (150a, 150b, 150c) contain nitrogen and chromium. The nitrogen content of the third absorber portion (150c) may be greater than that of the first absorber portion (150a) and less than that of the second absorber portion (150b). The boundary between the first to third absorber portions (150a, 150b, 150c) may or may not be visible. In FIG. 4a and FIG. 4b, any one of the first to third absorber portions (150a, 150b, 150c) may further include oxygen. The first to third absorbent portions (150a, 150b, 150c) may also be referred to as the first to third sub-absorbent membranes. That is, the absorbent pattern (150) comprises the first to third sub-absorbent membranes (150a, 150b, 150c) stacked in sequence, and the nitrogen content within the first to third sub-absorbent membranes (150a, 150b, 150c) may differ from one another.

[0039] Alternatively, as shown in FIG. 4c, the nitrogen content may gradually and continuously increase as the distance from the upper surface of the capping membrane (130) within the absorber pattern (150) increases. Conversely, the nitrogen content may gradually and continuously decrease as the distance from the upper surface of the capping membrane (130) within the absorber pattern (150) increases.

[0041] FIG. 5 is a drawing showing a part of a phase inversion mask according to embodiments of the present invention.

[0042] Referring to FIG. 5, the capping film (130) may have a first thickness (T1) in a direction perpendicular to the first surface (100a) of the substrate (100). The buffer pattern (140) may have a second thickness (T2) in a direction perpendicular to the first surface (100a) of the substrate (100). The absorber pattern (150) may have a third thickness (T3) in a direction perpendicular to the first surface (100a) of the substrate (100). The third thickness (T3) may be greater than the first thickness (T1) and the second thickness (T2). The absorber pattern (150) may have a refractive index (n2) smaller than 1, which is the refractive index (n1) of a vacuum. The refractive index of the absorber pattern (150) may be smaller than the refractive index of the buffer pattern (140). The absorption coefficient of the absorber pattern (150) may be greater than the absorption coefficients of the capping film (130) and the buffer pattern (140).

[0043] When the absorber pattern (150) is made of chromium nitride, for example, when the nitrogen content is about 10 at.%, the experimental refractive index value (n) of chromium nitride calculated by the Fresnel equation is about 0.927, and the absorption coefficient is about 0.039. When the buffer pattern (140) is made of silicon, the refractive index may be about 1. When the buffer pattern (140) is made of TaBN, the refractive index may be about 0.949.

[0044] Referring to FIG. 5, a first extreme ultraviolet (IL1) and a second extreme ultraviolet (IL2) may be incident toward a first surface (100a) of the substrate (100). The first extreme ultraviolet (IL1) and the second extreme ultraviolet (IL2) may have, for example, a first wavelength (λ1, for example, about 13.5 nm). The first extreme ultraviolet (IL1) may be incident through the opening (150P) and reflected from the surface of the reflective layer (120) to become a first reflected extreme ultraviolet (RL1). The second extreme ultraviolet (IL2) may be incident through the absorber pattern (150) and reflected from the surface of the reflective layer (120) to become a second reflected extreme ultraviolet (RL2). Since a portion of the second extreme ultraviolet (IL2) is absorbed within the absorber pattern (150), the amplitude of the second reflected extreme ultraviolet (RL2) may be smaller than the amplitude of the second extreme ultraviolet (IL2).

[0045] The absorber pattern (150) may absorb a portion of the second extreme ultraviolet rays (IL2). Accordingly, the reflectance of the second extreme ultraviolet rays (IL2) incident on the absorber pattern (150) may be smaller than the reflectance of the first extreme ultraviolet rays (IL1) incident on the apertures (150P). The reflectance of the extreme ultraviolet rays (IL1) incident on the absorber pattern (150) may vary depending on the absorption coefficient (k) of the material constituting the absorber pattern (150) and the thickness of the absorber pattern (150). For example, the smaller the absorption coefficient (k) of the material constituting the absorber pattern (150) and the smaller the thickness of the absorber pattern (150), the greater the reflectance of the second extreme ultraviolet rays (IL2) incident on the absorber pattern (150).

[0046] The absorber pattern (150) can shift the phase of the second reflected extreme ultraviolet (RL2). As the refractive index of the medium decreases, the wavelength of light passing through the medium can increase. Since the refractive index of the absorber pattern (150) is lower than the refractive index of a vacuum, the first wavelength (λ1) of the second extreme ultraviolet (RL2) in a vacuum can increase to the second wavelength (λ2) within the absorber pattern (150). Due to this change in wavelength within the absorber pattern (150), the phase of the second reflected extreme ultraviolet (RL2) passing through the absorber pattern (150) can differ from the phase of the first reflected extreme ultraviolet (RL1). The lower the refractive index of the material constituting the absorber pattern (150), and the greater the thickness of the absorber pattern (150), the greater this phase difference can be.

[0047] The first thickness (T1) of the capping film (130) and the second thickness (T2) of the buffer pattern (140) may be smaller than the first wavelength (λ1). Thus, the capping film (130) and the buffer pattern (140) may have a relatively weak influence on the phase shift of the second reflected extreme ultraviolet (RL2). The third thickness (T3) of the absorber pattern (150) may be larger than the first wavelength (λ1). Thus, the absorber pattern (150) may have a dominant influence on the phase shift of the second reflected extreme ultraviolet (RL2).

[0048] Preferably, the first thickness (T1) and the second thickness (T2) may be about 0.29 to 0.75 times the first wavelength (λ1) of the extreme ultraviolet rays (IL1, IL2). The third thickness (T3) may be about 2.96 to 4.08 times the first wavelength (λ1) of the extreme ultraviolet rays (IL1, IL2). When the first wavelength (λ1) of the extreme ultraviolet rays (IL1, IL2) is about 13.5 nm, preferably, the first thickness (T1) and the second thickness (T2) may each be independently 4 to 10 nm, and the third thickness (T3) may be 40 to 55 nm. The absorber pattern (150) has such a thickness (T3) that the second reflected extreme ultraviolet (RL2) can have a phase difference of about 170° to 235° with the first reflected extreme ultraviolet (RL1).

[0049] Due to this phase difference, destructive interference may occur between the second reflected extreme ultraviolet (RL2) and the first reflected extreme ultraviolet (RL1). When an exposure process using the phase inversion mask (500) is performed on a photoresist film formed on the wafer (50) of FIG. 1, the intensity of the extreme ultraviolet irradiated on the regions of the photoresist film corresponding to the absorber patterns (150) may be reduced due to destructive interference between the reflected extreme ultraviolet rays (RL1, RL2). That is, the image projected onto the photoresist film may have a high NILS (Normalized image log slope), and accordingly, it may be easy to realize a high-resolution image on the photoresist film.

[0051] FIG. 6a is a graph showing NILS values ​​according to the thickness of the absorber pattern of the phase inversion mask according to embodiments of the present invention.

[0052] Referring to FIG. 6a, in a structure in which 4 nm of ruthenium is adopted as the capping film (130), 4 nm of TaBO as the buffer pattern (140), and chromium nitride (CrN) as the absorber pattern (150) (where the content of nitrogen and chromium is fixed to approximately 10 at.% uniformly throughout the absorber pattern (150)), NILS values ​​according to the thickness of the absorber pattern (150) were simulated and shown in FIG. 6a when the absorber pattern (150) has a shape of a Line and Space (L / S) pattern with a pitch of 36 nm (1x) (i.e., the width of the line pattern is 18 nm and the spacing between the line patterns is 18 nm) and when it has a pattern shape of a contact hole structure with the same pitch. In FIG. 6a, for both the L / S pattern and the hole structure pattern, a maximum NILS value (approx. 2.75 for the L / S pattern) was observed when the thickness of the absorber pattern made of chromium nitride (CrN) was approximately 48.5 nm. In addition, a very high NILS value (approx. 2.70 for the L / S pattern) was observed when the thickness of the absorber pattern was approximately 42 nm. Overall, excellent NILS values ​​(approx. 2.35 to 2.75 for the L / S pattern) were observed when the thickness of the absorber pattern (150) was approximately 40 to 55 nm. Therefore, through FIG. 6a, it can be seen that the desirable thickness of the absorber pattern (150) made of chromium nitride (CrN) is approximately 40 to 55 nm.

[0054] FIG. 6b is a graph showing NILS values ​​according to the thickness of the absorber pattern of the phase inversion mask according to embodiments of the present invention.

[0055] Referring to FIG. 6b, the transmittance and phase difference in a phase inversion mask according to the thickness of an absorber pattern having an L / S pattern shape under the same conditions as FIG. 6a were simulated and are shown in FIG. 6a. Here, transmittance is the relative reflectance with respect to the reflective layer (120) (i.e., Transmittance = R ABS / R ML , R ABSis the reflectance, R of the absorber pattern (150). ML The reflectance of the reflective layer (120) may be. In FIG. 6b, overall, as the thickness of the absorber pattern increases, the transmittance decreases while the phase difference may increase. When the thickness of the absorber pattern (150) is about 40 to 55 nm, the phase difference is about 170° to 235°, and the transmittance may be about 0.8 to 7.5%. When the thickness of the absorber pattern made of chromium nitride (CrN) is about 48.5 nm, the phase difference is about 216° and the transmittance is about 3.5%, so the case where the thickness of the absorber pattern is about 48.5 nm is determined to be the optimal condition. A phase inversion mask (500) having such optimal conditions can suppress the sidelobe problem that occurs when the absorber pattern is applied with ruthenium or molybdenum. Thus, the phase inversion mask (500) can be applied to the manufacturing process of all semiconductor devices, including logic devices.

[0057] FIG. 6c is a graph showing NILS values ​​according to dose amount in phase inversion masks according to embodiments and comparative examples of the present invention.

[0058] Referring to FIG. 6c, in a phase inversion mask according to an embodiment of the present invention, as in FIG. 6a, ruthenium of 4 nm is adopted as the capping film (130), TaBO of 4 nm as the buffer pattern (140), and chromium nitride (CrN) of 48.5 nm as the absorber pattern (150), and the absorber pattern is set to have an L / S pattern shape. In addition, in a phase inversion mask according to a comparative example, TaBN of 54.5 nm is adopted as the absorber pattern, and all other structures are set identically to the phase inversion mask according to the embodiment of the present invention. For these phase inversion masks, NILS values ​​according to the dose amount of the light source were simulated and are shown in FIG. 6c. In FIG. 6c, it can be seen that the NILS values ​​of the phase inversion mask according to the embodiment of the present invention are generally higher than those of the comparative example. For example, in the comparative example, when the dose amount is about 67 mJ, it shows a NILS value of about 2.5, whereas in the embodiment, at the same dose amount (67 mJ), it can show a NILS value of about 2.725, which can be increased by about 9%. In addition, in the embodiment, only about 50 mJ of dose is required to show the same NILS value (about 2.5) as in the comparative example, so the dose amount can be reduced by about 25%. Thus, it can be seen that when using the phase inversion mask (500) according to the embodiments of the present invention, productivity improvement through increased throughput is possible, and it can have a direct effect on improving patterning quality, such as reducing LER (Line Edge Roughness) and LCDU (Local Critical Dimension Uniformity), and reducing SLO (single line open) or Missing Contact. Thus, when performing an exposure process on a photoresist film using the above-mentioned phase inversion mask (500), a photoresist pattern having a fine pitch and an accurate shape can be manufactured. An etching target film can be etched using the above-mentioned photoresist pattern.By performing patterning with the above photoresist pattern, a method for manufacturing a semiconductor device can be provided that can reduce process defects and improve productivity.

[0060] FIGS. 7a to 7c are cross-sectional views illustrating the processes of manufacturing the phase inversion mask of FIG. 3 according to embodiments of the present invention.

[0061] Referring to FIG. 7a, a substrate (100) may be provided. The substrate (100) may include a material having a low coefficient of thermal expansion. For example, the substrate (100) may include glass or silicon (Si). The substrate (100) may include the pattern region (PA) and the black border region (BA) as described with reference to FIG. 2.

[0062] A lower conductive layer (110) may be formed on a second surface (100b) of the substrate (100). The lower conductive layer (110) may include, for example, CrN and may be formed using a sputtering deposition process.

[0063] A reflective layer (120) may be formed on a first surface (100a) of the substrate (100). Forming the reflective layer (120) may include forming low-refractive-index layers (122) and high-refractive-index layers (124) alternately and repeatedly on the first surface (100a) of the substrate (100). The low-refractive-index layers (122) and the high-refractive-index layers (124) may each be stacked about 40 to about 60 times and, for example, may be formed using a sputtering deposition process. According to some embodiments, forming the reflective layer (120) may include performing a laser annealing process on a second portion (S2) on the black border region (BA). Thus, the low-refractive-index layers (122) and the high-refractive-index layers (124) of the second part (S2) can be intermixed by the laser annealing process. Accordingly, the reflective layer (120) may have a first part (S1) in which the low-refractive-index layers (122) and the high-refractive-index layers (124) are alternately stacked on the pattern area (PA), and a second part (S2) in which the low-refractive-index layers (122) and the high-refractive-index layers (124) are intermixed on the black border area (BA).

[0064] A capping film (130) may be formed on the reflective layer (120). The capping film (130) may include ruthenium, for example, and may be formed using a sputtering deposition process. The capping film (130) may be formed with a first thickness (T1) as described in FIG. 5.

[0065] A buffer film (140L) may be formed on the capping film (130). The buffer film (140L) may be formed with a second thickness (T2) as described in FIG. 5. The buffer film (140L) may include a material having etch selectivity with respect to the capping film (130). The buffer film (140L) may also be referred to as an etch stop film. Additionally, the buffer film (140L) may include a material having etch selectivity with respect to the absorber film (150L) to be described later. As an example, the buffer film (140L) may include at least one selected from Si, SiN, SiO2, SiON, TaBO, TaO, TaON, TaN, TaBN, TiN, Nb, and Ta. The material constituting the buffer film (140L) may be appropriately selected according to the type of etching gas that forms the subsequent absorber pattern (150). The above buffer film (140L) can be formed, for example, by chemical vapor deposition, sputtering deposition, etc.

[0066] An absorbent film (150L) may be formed on the buffer film (140L). The absorbent film (150L) may be formed with a third thickness (T3) as described in FIG. 5. The absorbent film (150L) may be formed, for example, using chemical vapor deposition, sputtering deposition, etc. The absorbent film (150L) may be formed to contain nitrogen and chromium. The absorbent film (150L) may further contain oxygen. The absorbent film (150L) may be formed as a single film having a uniform composition of nitrogen and chromium throughout. The absorbent film (150L) may be formed as a multi-film in which the composition of nitrogen and chromium changes with height. The absorbent film (150L) may be formed to have a nitrogen content profile as described with reference to FIG. 4a to 4c. To this end, when depositing the absorber film (150L), the nitrogen gas flow rate and sputtering conditions may be varied. The absorber film (150L) may further contain oxygen. The absorber film (150L) may contain at least one of chromium nitride and chromium nitride oxide.

[0067] Referring to FIG. 7b, a laser can be irradiated onto a second part (S2) of the reflective layer (120) on the black border region (BA) to anneale the second part (S2) and form an intermixing structure.

[0068] Referring to FIGS. 7b and 7c, a mask pattern (MK) is formed on the absorber film (150L). The mask pattern (MK) may be formed of the same or different material as the buffer film (140L). The mask pattern (MK) may be a photoresist pattern. Alternatively, the mask pattern (MK) may be a hard mask, and the mask pattern (MK) may include a silicon-containing film, a metal-containing film, a metal nitride, or a metal oxide. Specifically, the mask pattern (MK) may include at least one selected from SiN, SiO2, SiON, TaBO, TaO, TaON, TaN, TaBN, TiN, Nb, and Ta. The material constituting the mask pattern (MK) may be appropriately selected according to the type of etching gas used to form the subsequent absorber pattern (150).

[0069] The above mask pattern (MK) is used as an etching mask to etch the absorber film (150L) to form absorber patterns (150), and openings (150P) are formed between the absorber patterns (150) to expose the upper surface of the buffer film (140L). At this time, the etching gas used to etch the absorber film (150L) may be a fluorine-based gas containing fluorine or a chlorine-based gas containing chlorine. Examples of fluorine-based etching gases may include SF6, CF4, and CHF3. Examples of chlorine-based etching gases may include Cl2. When the absorber film (150L) is etched with a fluorine-based gas, SiN, SiO2, SiON, TaBO, TaO, and TaON may be used for the mask pattern (MK) and the buffer film (140L). When the above absorbent film (150L) is etched with a chlorine-based material, TaN, TaBN, TiN, Nb, and Ta may be used as the mask pattern (MK) and buffer film (140L).

[0070] Referring to FIG. 7c and FIG. 3, an anisotropic etching process is performed to remove the mask pattern (MK). At this time, the buffer film (140L) is also etched to form buffer patterns (140) and the upper surface of the capping film (130) may be exposed. The capping film (130) has excellent etch selectivity with respect to the buffer film (140L) and is hardly damaged during the anisotropic etching process. Thus, the phase inversion mask (500) of FIG. 3 can be manufactured.

[0071] Subsequently, the phase inversion mask (500) can be cleaned, and the surface of the phase inversion mask (500) can be inspected for any etched damage. If etched damage is found, a repair process can be performed. The repair process can be performed using a repair gas containing xenon (Xe) and fluorine gas.

[0072] Meanwhile, in the absence of the buffer film (140L), there is almost no etching selectivity between the chromium nitride constituting the absorber film (150L) and the ruthenium constituting the capping film (130), so the upper surface of the capping film (130) may be etched and damaged during the etching process for forming the absorber pattern (150). In this case, if the capping film (130) is formed of ruthenium, it does not react with the repair gas used in the repair process, making it difficult to heal the upper surface of the capping film (130). However, in the present invention, by using a buffer film (140L) that has excellent etching selectivity with the capping film (130) and the absorber film (150L), etching damage to the upper surface of the capping film (130) is eliminated, thereby reducing process defects and improving productivity, while simultaneously manufacturing a phase inversion mask of excellent quality.

[0073] If the absorber pattern (150) is made of a material other than chromium nitride, such as ruthenium, molybdenum, palladium, rhodium, platinum, or silver, it is difficult to carry out the etching process with an etching gas containing fluorine or chlorine, which may increase process defects and reduce productivity. The present invention can improve productivity by adopting chromium nitride, which has high feasibility, as the absorber pattern (150).

[0075] FIG. 8 is a cross-sectional view of a phase inversion mask according to embodiments of the present invention.

[0076] Referring to FIG. 8, in the phase inversion mask (501) according to the present example, a buffer film (140L) is positioned directly on the reflective layer (120). The front surface of the reflective layer (120) can come into direct contact with the buffer film (140L). At this time, the buffer film (140L) may be made of a silicon-containing film. Specifically, the buffer film (140L) may include at least one selected from Si, SiN, SiO2, and SiON. The absorber pattern (150) may have the material and structure described with reference to FIG. 3 to FIG. 5. The absorber pattern (150) may be placed on the buffer film (140L). The buffer film (140L) may not only serve as an etching prevention pattern when forming the absorber pattern (150), but also serve as a capping film that prevents etching damage to the reflective layer (120) and protects the reflective layer (120). In this example, the buffer film (140L) may also be referred to as an etch stop film or a capping film. The buffer film (140L) may have a second thickness (T2) as described in FIG. 5. The absorber pattern (150) may have a third thickness (T3) as described in FIG. 5. The description of the second thickness (T2) and the third thickness (T3) may be the same as described above. The refractive index of the buffer film (140L) may be greater than the refractive index of the absorber pattern (150). The upper surface of the buffer film (140L) may be exposed through the opening (150P) between the absorber patterns (150). Other structures may be the same or similar as described with reference to FIG. 3 to FIG. 5.

[0078] Figure 9 is a cross-sectional view showing the process of manufacturing the phase inversion mask of Figure 8.

[0079] Referring to FIG. 9, a lower conductive layer (110) is formed on a second surface (100b) of a substrate (100). A reflective layer (120), a buffer film (140L), and an absorber film (150L) are formed sequentially on a first surface (100a) of the substrate (100). At this time, a capping film (130) may be omitted. A laser is irradiated to form an intermixed structure in a second portion (S2) of the reflective layer (120). Then, a mask pattern (MK) is formed on the absorber film (150L). The mask pattern (MK) may be formed from a material having etch selectivity simultaneously with the absorber film (150L) and the buffer film (140L). The mask pattern (MK) may be a photoresist pattern. Alternatively, the mask pattern (MK) may include at least one selected from TaBO, TaO, TaON, TaN, TaBN, TiN, Nb, and Ta. The absorber film (150L) is etched using the mask pattern (MK) to form absorber patterns (150), and the upper surface of the buffer film (140L) is exposed through the opening (150P) between them. Then, with reference to FIG. 8, only the mask pattern (MK) can be selectively removed to expose the upper surfaces of the absorber patterns (150).

[0080] In the phase inversion mask (501) according to the present example, the capping film (130) of FIG. 3, which is made of ruthenium, is omitted, so the process can be simplified and the yield can be improved.

[0082] The above description of the embodiments of the present invention provides examples for explaining the present invention. Accordingly, the present invention is not limited to the above embodiments, and it is evident that many modifications and changes are possible within the technical scope of the present invention, such as combining the above embodiments by those skilled in the art. Explanation of the symbols

[0083] 100: Substrate 110: Lower conductive layer 120: Reflective layer 130: Capping film 140: Buffer pattern 150: Absorber pattern

Claims

Claim 1 A phase inversion mask for extreme ultraviolet lithography comprising: a substrate; a reflective layer on the substrate; a capping film disposed on the reflective layer; a buffer pattern disposed on the capping film and providing an opening that exposes the surface of the capping film; and an absorber pattern covering the buffer pattern, wherein the buffer pattern comprises a material having etch selectivity with respect to the absorber pattern and the capping film, the refractive index of the absorber pattern is smaller than the refractive index of the buffer pattern, the absorber pattern comprises at least one of chromium nitride (CrN) and chromium nitride oxide (CrON), the nitrogen content within the absorber pattern varies with distance from the buffer pattern, and the extreme ultraviolet light reflected through the absorber pattern has a phase difference of 170° to 235° with respect to the extreme ultraviolet light reflected through the opening. Claim 2 A phase inversion mask for extreme ultraviolet lithography according to claim 1, wherein the width of the absorber pattern and the width of the buffer pattern are the same, and the thickness of the absorber pattern is greater than the thickness of each of the buffer pattern and the capping film. Claim 3 A phase inversion mask for extreme ultraviolet lithography according to claim 1, wherein the nitrogen content in the absorber pattern is 5 to 70 at.%. Claim 4 A phase inversion mask for extreme ultraviolet lithography according to claim 1, wherein the absorber pattern comprises a first sub-absorber film and a second sub-absorber film stacked in sequence, and the nitrogen content in the first sub-absorber film is different from the nitrogen content in the second sub-absorber film. Claim 5 A phase inversion mask for extreme ultraviolet lithography according to claim 1, wherein the thickness of the absorber pattern is 40 to 55 nm and the thickness of the buffer pattern is 4 to 10 nm. Claim 6 In claim 1, the buffer pattern is a phase inversion mask for extreme ultraviolet lithography comprising at least one selected from Si, SiN, SiO2, SiON, TaBO, TaO, TaON, TaN, TaBN, TiN, Nb, and Ta. Claim 7 A phase inversion mask for extreme ultraviolet lithography according to claim 1, wherein the thickness of each of the buffer pattern and the capping film is smaller than the wavelength of extreme ultraviolet light incident on a substrate. Claim 8 A phase inversion mask for extreme ultraviolet lithography comprising: a substrate on a conductive layer; a reflective layer on the substrate; a capping film disposed on the reflective layer; an absorber pattern disposed on the capping film and providing an opening that exposes the surface of the capping film; and a buffer pattern between the absorber pattern and the capping film that exposes the surface of the capping film, wherein the buffer pattern comprises a material having etch selectivity with respect to the absorber pattern and the capping film, wherein the absorber pattern comprises nitrogen and chromium, wherein the content of the nitrogen within the absorber pattern varies continuously with distance from the buffer pattern, and wherein the extreme ultraviolet reflected through the absorber pattern has a phase difference with respect to the extreme ultraviolet reflected through the opening. Claim 9 A phase inversion mask for extreme ultraviolet lithography according to claim 8, wherein the capping film comprises a material having etch selectivity with respect to the absorber pattern, and the thickness of the absorber pattern is greater than the thickness of the capping film. Claim 10 In claim 9, the capping film is a phase inversion mask for extreme ultraviolet lithography comprising at least one selected from Si, SiN, SiO2, and SiON. Claim 11 In claim 8, the absorber pattern is a phase inversion mask for extreme ultraviolet lithography that further includes oxygen. Claim 12 In claim 8, the width of the absorber pattern and the width of the buffer pattern are the same, and the thickness of each of the capping film and the buffer pattern is smaller than the wavelength of the extreme ultraviolet rays incident on the substrate, forming a phase inversion mask for extreme ultraviolet lithography. Claim 13 delete Claim 14 In claim 8, the buffer pattern comprises at least one selected from Si, SiN, SiO2, SiON, TaBO, TaO, TaON, TaN, TaBN, TiN, Nb, and Ta, and the capping film comprises ruthenium, a phase inversion mask for extreme ultraviolet lithography. Claim 15 A phase inversion mask for extreme ultraviolet lithography according to claim 8, wherein the thickness of the absorber pattern is 40 to 55 nm and the thickness of the buffer pattern is 4 to 10 nm. Claim 16 In claim 8, the substrate comprises a black border region and a pattern region, the reflective layer comprises low-refractive-index layers and high-refractive-index layers stacked alternately, and the low-refractive-index layers and the high-refractive-index layers on the black border region are intermixed phase inversion masks for extreme ultraviolet lithography. Claim 17 A phase inversion mask for extreme ultraviolet lithography comprising: a substrate; a reflective layer on the substrate; a capping film disposed on the reflective layer; a buffer pattern disposed on the capping film and providing an opening that exposes the surface of the capping film; and an absorber pattern covering the buffer pattern, wherein the buffer pattern comprises a material having etch selectivity with respect to the absorber pattern and the capping film, the buffer pattern and the absorber pattern have the same width, the thickness of each of the capping film and the buffer pattern is smaller than the wavelength of extreme ultraviolet rays incident on the substrate, the absorber pattern comprises nitrogen and chromium, the content of the nitrogen within the absorber pattern varies continuously with distance from the buffer pattern, and is configured such that extreme ultraviolet rays reflected through the absorber pattern have a phase difference with respect to extreme ultraviolet rays reflected through the opening. Claim 18 A phase inversion mask for extreme ultraviolet lithography according to claim 17, wherein the refractive index of the absorber pattern is smaller than the refractive index of the buffer pattern and the thickness of the absorber pattern is larger than the thickness of the buffer pattern. Claim 19 delete Claim 20 In claim 17, the buffer pattern is a phase inversion mask for extreme ultraviolet lithography comprising at least one selected from Si, SiN, SiO2, SiON, TaBO, TaO, TaON, TaN, TaBN, TiN, Nb, and Ta.

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