EUV interference lithography system

Abstract

Provided is an EUV interference lithography system in which an interference fringe is formed in a photoresist by a plurality of diffracted light beams transmitted and diffracted from a transmissive mask, wherein the transmissive mask includes: a first pattern region and a second pattern region spaced apart from each other by a first distance; and a third pattern region and a fourth pattern region spaced apart from each other by a second distance greater than the first distance with the first pattern region and the second pattern region therebetween, and a plurality of patterns in the first to fourth pattern regions have the same pitch size.

Description

EUV interference lithography system

[0001] The present invention relates to an EUV interference lithography system for evaluating EUV photoresists.

[0002] The exposure process technology using EUV wavelength light, which has been applied to form ultra-fine semiconductor circuit patterns below the 7 nm node, is also beginning to be applied to processes below the 5 nm node, and is a technology that is promised to be applied to next-generation processes below the 2 nm node.

[0003] In order for EUV exposure technology to be applied to processes below the 2 nm node to form ultra-fine semiconductor circuit patterns, it is essential to develop photoresists with high EUV light sensitivity, excellent line edge roughness characteristics, and high resolution. In order to develop next-generation EUV photoresists, it is essential to develop evaluation technology using an EUV light source, and interference lithography technology is a technology for evaluating EUV photoresists using an EUV light source.

[0004] FIG. 1 is a drawing for explaining a conventional EUV interference lithography technique, FIG. 2 is a drawing for explaining a first pattern area of ​​a transmissive mask used in a conventional EUV interference lithography technique, and FIG. 3 is a drawing for explaining an interference pattern formed in a photoresist by a conventional EUV interference lithography technique.

[0005] Referring to FIGS. 1 to 3, a conventional EUV interference lithography technique for evaluating an EUV photoresist uses a transmissive mask (100) to form an EUV interference pattern with high energy efficiency on a photoresist (PR). More specifically, the transmissive mask (100) has a structure in which a pattern layer (120) including molybdenum (Mo) is formed on a membrane (110) including silicon nitride (SiN), and the pattern layer (120) may have a pattern region (P1, P2) and a non-pattern region. The non-pattern region may be defined as an region excluding the pattern regions (P1, P2), and the pattern region (P1, P2) may be defined as an region in which a plurality of patterns are arranged adjacent to each other.

[0006] Hereinafter, as illustrated in FIG. 1, a conventional EUV interference lithography technique is specifically described through a case where the pattern layer (120) includes a first pattern region (P1) and a second pattern region (P2). The first pattern region (P1) and the second pattern region (P2) are arranged to be spaced apart from each other by a specific distance (D), and the pitch size (q) of the patterns in the first pattern region (P1) and the pitch size (q) of the patterns in the second pattern region (P2) may be the same. In addition, the pitch size (q) may be defined as the sum of the width (w) of the pattern and the distance (d) between the patterns, as illustrated in FIG. 2.

[0007] When light (L) is irradiated to the above-mentioned transparent mask (100), the light (L) sequentially transmits through the membrane (110) and the pattern layer (120), but may be diffracted by the first pattern region (P1) and the second pattern region (P2), and an interference pattern (IF) may be formed on the photoresist (PR) by interference of the diffracted light diffracted from each of the first pattern region (P1) and the second pattern region (P2). For example, the -1-order diffracted light (DL1, -1) diffracted from the first pattern region (P1) st ) and the +1st order diffracted light (DL1, +1) diffracted from the second pattern area (P2) st ) can form an interference pattern (IF) on the photoresist (PR).

[0008] In this case, the interference pattern (IF) can be formed on the photoresist (PR) placed at a distance H from the transmissive mask (100), and the distance between the transmissive mask (100) and the photoresist (PR) can be derived through the following <Mathematical Formula 1>.

[0009] <Mathematical Formula 1>

[0010]

[0011] (H: distance between the above-mentioned transparent mask and the above-mentioned photoresist, D: distance between the above-mentioned first pattern region and the above-mentioned second pattern region, θ1: diffraction angle of the first-order diffracted light)

[0012] In addition, the diffraction angle of the first diffracted light can be determined by the pitch size (q) of the patterns in the first and second pattern areas (P1, P2), and can be derived through the following <Mathematical Formula 2> according to Bragg's law.

[0013] <Mathematical Formula 2>

[0014]

[0015] (m: diffraction order, λ: wavelength of the light, q: pitch size of patterns in the first and second pattern areas, θ m : diffraction angle of m-th order diffracted light)

[0016] In addition, the interference pattern (IF) is formed to have a period of p, as shown in FIG. 3, and the period of the interference pattern (IF) can be derived through <Mathematical Formula 3> below.

[0017] <Mathematical Formula 3>

[0018]

[0019] (p m : Period of the interference pattern formed by the mth diffracted light, λ: wavelength of the light, θ m : diffraction angle of m-th order diffracted light)

[0020] Conventional EUV interference lithography technology can evaluate the performance of the photoresist (PR) by using the interference pattern (IF) formed on the photoresist (PR) through the process described above.

[0021] However, since the reliability of the performance evaluation of the photoresist (PR) may decrease when the resolution of the interference pattern (IF) is low, improvement of the resolution of the interference pattern (IF) is necessary to improve the reliability of the performance evaluation of the photoresist (PR). Accordingly, the present invention aims to provide a technology for improving the resolution of an interference pattern formed on a photoresist in EUV interference lithography technology.

[0022]

[0023] The technical problem to be solved by the present invention is to provide an EUV interference lithography system for evaluating EUV photoresist.

[0024] Another technical problem to be solved by the present invention is to provide an EUV interference lithography system capable of improving the resolution of interference patterns.

[0025] Another technical problem to be solved by the present invention is to provide an EUV interference lithography system capable of improving the reliability of performance evaluation for EUV photoresists.

[0026] Another technical challenge that the present invention seeks to solve is to provide an EUV interference lithography system that can be used in the development of next-generation EUV photoresists.

[0027] The technical problems to be solved by the present invention are not limited to those described above.

[0028] To solve the above-described technical problems, the present invention provides an EUV interference lithography system.

[0029] According to one embodiment, in an EUV interference lithography system in which an interference pattern is formed on a photoresist by a plurality of diffracted lights transmitted and diffracted from a transmission mask, the transmission mask includes a first pattern region and a second pattern region spaced apart from each other by a first distance, a third pattern region and a fourth pattern region spaced apart from each other by a second distance greater than the first distance, with the first pattern region and the second pattern region interposed therebetween, and the plurality of patterns in the first to fourth pattern regions may include those having the same pitch size.

[0030] According to one embodiment, when EUV light is irradiated onto the transmissive mask, a first diffracted light is generated in the first pattern region, a second diffracted light is generated in the second pattern region, a third diffracted light is generated in the third pattern region, and a fourth diffracted light is generated in the fourth pattern region, wherein the interference pattern may include a pattern formed by interference of the first to fourth diffracted lights within a target region of the photoresist.

[0031] In one embodiment, the first and second diffracted lights may include relatively low-order diffracted lights, and the third and fourth diffracted lights may include relatively high-order diffracted lights.

[0032] According to one embodiment, the second distance may include that calculated through <Mathematical Formula 1> and <Mathematical Formula 4> below.

[0033] <Mathematical Formula 1>

[0034]

[0035] (H: distance between the above-mentioned transparent mask and the above-mentioned photoresist, D1: the first distance, θ1: diffraction angle of the first-order diffracted light)

[0036] <Mathematical Formula 4>

[0037]

[0038] (D2: the second distance, H: the distance between the transmissive mask and the photoresistor, θ2: the diffraction angle of the second-order diffracted light)

[0039] According to another embodiment, in an EUV interference lithography system in which an interference pattern is formed on a photoresist by a plurality of diffracted lights transmitted and diffracted from a transmission mask, the system may include a method in which relatively low-order diffracted light and relatively high-order diffracted light among the plurality of diffracted lights are irradiated and interfered within a target area of ​​the photoresist to form the interference pattern.

[0040] According to another embodiment, among the plurality of diffracted lights, relatively low-order diffracted lights are diffracted lights that are diffracted in a pattern area adjacent to a central portion of the transmissive mask and irradiated to the target area, and among the plurality of diffracted lights, relatively high-order diffracted lights are diffracted lights that are diffracted in a pattern area adjacent to an outer portion of the transmissive mask and irradiated to the target area.

[0041] According to another embodiment, the diffraction angle of a relatively low-order diffracted light among the plurality of diffracted lights may be smaller than the diffraction angle of a relatively high-order diffracted light among the plurality of diffracted lights.

[0042] According to another embodiment, in an EUV interference lithography system in which an interference pattern is formed on a photoresist by a plurality of diffracted lights transmitted and diffracted from a transmissive mask, the transmissive mask may include a first pattern region and a second pattern region spaced apart from each other by a first distance, a third pattern region and a fourth pattern region spaced apart from each other by a second distance greater than the first distance, with the first pattern region and the second pattern region interposed therebetween, and the plurality of patterns in the first and second pattern regions may have a first pitch size, and the plurality of patterns in the third and fourth pattern regions may have a second pitch size smaller than the first pitch size.

[0043] According to another embodiment, when EUV light is irradiated onto the transmissive mask, a first diffracted light is generated in the first pattern region, a second diffracted light is generated in the second pattern region, a third diffracted light is generated in the third pattern region, and a fourth diffracted light is generated in the fourth pattern region, wherein the interference pattern may include a pattern formed by interference of the first to fourth diffracted lights within a target region of the photoresist.

[0044] According to another embodiment, the first to fourth diffracted lights may all include first-order diffracted lights.

[0045] According to another embodiment, the second pitch size may include those calculated through <Mathematical Formula 3> and <Mathematical Formula 6> below.

[0046] <Mathematical Formula 3>

[0047]

[0048] (p m : The period of the interference pattern formed on the photolithography by the m-th diffracted light, θ m : diffraction angle of m-th order diffracted light)

[0049] <Mathematical Formula 6>

[0050]

[0051] (q2: the second pitch size, m: diffracted light order, p m : Period of the interference pattern formed on the photolithography by the m-th diffracted light)

[0052] According to another embodiment, the second distance may include that calculated through <Mathematical Formula 7> below.

[0053] <Mathematical Formula 7>

[0054]

[0055] (D3: the second distance, H: the distance between the transparent mask and the photoresistor, θ diff : Diffraction angle of the third and fourth diffracted rays above)

[0056] According to another embodiment, in an EUV interference lithography system in which an interference pattern is formed on a photoresist by a plurality of diffracted lights transmitted and diffracted from a transmissive mask, the system may include irradiating and interfering a target area of ​​the photoresist with diffracted lights having the same order but different diffraction angles among a plurality of diffracted lights transmitted and diffracted in different pattern areas of the transmissive mask, so that the interference pattern is formed.

[0057] According to another embodiment, the interference pattern may be formed by interference between diffracted light transmitted and diffracted in a pattern region having a relatively large pitch size among the plurality of diffracted lights and diffracted light transmitted and diffracted in a pattern region having a relatively small pitch size.

[0058] An EUV interference lithography system according to an embodiment of the present invention forms a final interference pattern through the interference of an interference pattern having a relatively small periodic frequency and an interference pattern having a relatively high periodic frequency, and can evaluate the performance of an EUV photoresist through the formed final interference pattern.

[0059] Accordingly, the Normalized Image Log Slope (NILS) can be improved compared to the interference pattern formed through conventional EUV interference lithography technology, so that the point spread function can be suppressed, and the distinction between two consecutive lines of the interference pattern can be clearly distinguished, thereby improving the resolution. In addition, since the reliability of the performance evaluation of EUV photoresists can be improved due to the above-described effect, it can be easily applied to the development of next-generation high-performance EUV photoresists.

[0060] Figure 1 is a drawing for explaining conventional EUV interference lithography technology.

[0061] FIG. 2 is a drawing for explaining a first pattern area of ​​a transmission mask used in conventional EUV interference lithography technology.

[0062] Figure 3 is a drawing for explaining an interference pattern formed on a photoresist by conventional EUV interference lithography technology.

[0063] FIG. 4 is a drawing for explaining an EUV interference lithography system according to a first embodiment of the present invention.

[0064] FIG. 5 is a drawing for explaining first to fourth pattern areas of a transmission mask used in an EUV interference lithography system according to a first embodiment of the present invention.

[0065] FIG. 6 is a drawing for explaining the diffraction angles of the first-order diffraction light and the second-order diffraction light in the EUV interference lithography system according to the first embodiment of the present invention.

[0066] Figures 7 and 8 are drawings for explaining the principle of improving resolution through frequency control of interference patterns.

[0067] FIG. 9 is a drawing for explaining an EUV interference lithography system according to a second embodiment of the present invention.

[0068] FIG. 10 is a drawing for explaining first to fourth pattern areas of a transmission mask used in an EUV interference lithography system according to a second embodiment of the present invention.

[0069] Figure 11 is a drawing for explaining the process margin of the D value used in the EUV interference lithography system.

[0070] Figure 12 is a drawing for explaining the process margin of the H value used in the EUV interference lithography system.

[0071] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. However, the technical concept of the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete and to sufficiently convey the spirit of the present invention to those skilled in the art.

[0072] In this specification, when a component is referred to as being on another component, it means that it can be formed directly on the other component, or a third component may be interposed between them. In addition, in the drawings, the thicknesses of films and regions are exaggerated for the purpose of effectively explaining the technical contents.

[0073] Also, although terms such as first, second, and third have been used to describe various components in various embodiments of this specification, these components should not be limited by these terms. These terms are only used to distinguish one component from another. Thus, what is referred to as a first component in one embodiment may be referred to as a second component in another embodiment. Each embodiment described and illustrated herein also includes its complementary embodiments. Also, the term "and / or" has been used herein to mean including at least one of the components listed before and after.

[0074] In the specification, singular expressions include plural expressions unless the context clearly dictates otherwise. In addition, terms such as "comprise" or "have" are intended to specify the presence of a feature, number, step, component, or combination thereof described in the specification, and should not be construed as excluding the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof. In addition, in the present specification, "connection" is used to mean both indirectly connecting multiple components and directly connecting them.

[0075] In addition, when describing the present invention below, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

[0076]

[0077] EUV interference lithography system according to the first embodiment

[0078] FIG. 4 is a drawing for explaining an EUV interference lithography system according to a first embodiment of the present invention, FIG. 5 is a drawing for explaining first to fourth pattern areas of a transmission mask used in an EUV interference lithography system according to a first embodiment of the present invention, FIG. 6 is a drawing for explaining diffraction angles of first-order diffraction light and second-order diffraction light in an EUV interference lithography system according to a first embodiment of the present invention, and FIGS. 7 and 8 are drawings for explaining a principle of improving resolution through frequency control of an interference pattern.

[0079] Referring to FIGS. 4 and 5, a transmissive mask (100) included in an EUV interference lithography system according to the first embodiment includes a membrane (110) including silicon nitride (SiN), and a pattern layer (120) disposed on the membrane (110) and including molybdenum (Mo), wherein the pattern layer (120) may include first to fourth pattern regions (P1, P2, P3, P4). According to one embodiment, the first to fourth pattern regions (P1, P2, P3, P4) may be defined as different regions each including a plurality of patterns.

[0080] According to one embodiment, the first pattern region (P1) and the second pattern region (P2) are pattern regions arranged adjacent to the central portion of the transmissive mask (100), and may be arranged to be spaced apart from each other by a first distance (D1). More specifically, the first distance (D1) may be defined as the distance between the central portion of the first pattern region (P1) and the central portion of the second pattern region (P2).

[0081] In contrast, the third pattern area (P3) and the fourth pattern area (P4) are pattern areas arranged adjacent to the outer portion of the transparent mask (100), and may be arranged to be spaced apart from each other by a second distance (D2). More specifically, the second distance (D2) may be defined as the distance between the center portion of the third pattern area (P3) and the center portion of the fourth pattern area (P4). In addition, the second distance (D2) may be longer than the first distance (D1).

[0082] That is, the transparent mask (100) may be arranged so that the first pattern area (P1) and the second pattern area (P1) are spaced apart from each other by the first distance (D1) in the central portion, and the third pattern area (P3) and the fourth pattern area (P4) are spaced apart from each other by the second distance (D2) with the first pattern area (P1) and the second pattern area (P2) interposed therebetween.

[0083] In addition, as illustrated in FIG. 5, the plurality of patterns within the first to fourth pattern areas (P1, P2, P3, P4) may all have the same pitch size (q). That is, the pitch sizes of the plurality of patterns within the first pattern area (P1), the pitch sizes of the plurality of patterns within the second pattern area (P2), the pitch sizes of the plurality of patterns within the third pattern area (P3), and the pitch sizes of the plurality of patterns within the fourth pattern area (P4) may be the same.

[0084] When EUV light (L) is irradiated onto the transmissive mask (100), a plurality of diffracted lights may be generated by transmitting and diffracting the EUV light (L) from the transmissive mask (100). According to one embodiment, first to fourth diffracted lights may be generated in each of the first to fourth pattern areas (P1, P2, P3, and P4). More specifically, a first diffracted light may be generated in the first pattern area (P1), a second diffracted light may be generated in the second pattern area (P2), a third diffracted light may be generated in the third pattern area (P3), and a fourth diffracted light may be generated in the fourth pattern area (P4). The first to fourth diffracted lights may interfere within the target area (TA) of the photoresist (PR) to form an interference pattern.

[0085] In one embodiment, the first and second diffracted light may include relatively lower-order diffracted light, while the third and fourth diffracted light may include relatively higher-order diffracted light. For example, the first diffracted light may include -1-order diffracted light (DL1, -1 st ) and the second diffracted light is the +1st order diffracted light (DL1, +1 st ) may be included. In contrast, the third diffraction light may include the -2nd order diffraction light (DL2, -2 nd ) and the fourth diffracted light is +2 order diffracted light (DL2, +2 nd ) may be included.

[0086] According to one embodiment, the interference pattern may be formed on the photoresist (PR) placed at a distance H from the transmissive mask (100), and the distance between the transmissive mask (100) and the photoresist (PR) may be derived through the following <Mathematical Formula 1>.

[0087] <Mathematical Formula 1>

[0088]

[0089] (H: distance between the above-mentioned transparent mask and the above-mentioned photoresist, D1: the first distance, θ1: diffraction angle of the first-order diffracted light)

[0090] In addition, the diffraction angle of the first diffracted light can be determined by the pitch size (q) of the patterns in the first and second pattern areas (P1, P2), and can be derived through the following <Mathematical Formula 2> according to Bragg's law.

[0091] <Mathematical Formula 2>

[0092]

[0093] (m: diffraction order, λ: wavelength of the light, q: pitch size of patterns in the first and second pattern areas, θ m : diffraction angle of m-th order diffracted light)

[0094] In addition, the interference pattern is formed to have a period of p, and the period of the interference pattern can be derived through <Mathematical Formula 3> below.

[0095] <Mathematical Formula 3>

[0096]

[0097] (p m : Period of the interference pattern formed by the mth diffracted light, λ: wavelength of the light, θ m : diffraction angle of m-th order diffracted light)

[0098] As described above, in order for relatively low-order diffracted light (first-order diffracted light) and relatively high-order diffracted light (second-order diffracted light) to interfere within the target area (TA), the second distance (D2) can be controlled to a specific distance. For example, the second distance (D2) can be controlled to have a value calculated through the following <Mathematical Formula 4>.

[0099] <Mathematical Formula 4>

[0100]

[0101] (D2: the second distance, H: the distance between the transmissive mask and the photoresistor, θ2: the diffraction angle of the second-order diffracted light)

[0102] According to one embodiment, the diffraction angle of the second-order diffracted light can be derived through the above-described <Mathematical Formula 2>. That is, the diffraction angles of the first-order diffracted light and the second-order diffracted light can both be derived through the above-described <Mathematical Formula 2>.

[0103] As illustrated in Fig. 6, the diffraction angle (θ1) of the first-order diffracted light may be defined as the angle between the normal direction of the upper surface of the pattern layer (120) and the propagation direction of the first-order diffracted light. In contrast, the diffraction angle (θ2) of the second-order diffracted light may be defined as the angle between the normal direction of the upper surface of the pattern layer (120) and the propagation direction of the second-order diffracted light. As described above, when the second distance (D2) is longer than the first distance (D1) and the pitch sizes of the plurality of patterns in the first to fourth pattern areas (P1, P2, P3, P4) are the same, the diffraction angle (θ1) of the relatively low-order diffracted light (the first-order diffracted light) generated from the first and second pattern areas (P1, P2) may be smaller than the diffraction angle (θ2) of the relatively high-order diffracted light (the second-order diffracted light) generated from the third and fourth pattern areas (P3, P4).

[0104] In contrast, according to another embodiment, the diffraction angles (θ1, θ2) of the first-order diffracted light and the second-order diffracted light can also be calculated through the angle between the direction parallel to the upper surface of the photoresist (PR) and the direction in which the diffracted light is irradiated to the photoresist (PR), and the distance (A, B) between the target area (TA) and the pattern area.

[0105] For example, the diffraction angle (θ1) of the first diffraction light can be calculated using the distance (A) between the target area (TA) and the position where the second pattern area (P2) corresponds to the photoresist (PR), the distance (H) between the transmissive mask (100) and the photoresist (PR), and the angle between the direction parallel to the upper surface of the photoresist (PR) and the direction in which the diffraction light is irradiated to the photoresist (PR). In contrast, the diffraction angle (θ2) of the second-order diffraction light can be calculated using the distance (A+B) between the target area (TA) and the position where the fourth pattern area (P4) corresponds to the photoresist (PR), the distance (H) between the transmissive mask (100) and the photoresist (PR), and the angle between the direction parallel to the upper surface of the photoresist (PR) and the direction in which the diffraction light is irradiated to the photoresist (PR).

[0106] As a result, the EUV interference lithography system according to the first embodiment of the present invention can form the interference pattern as relatively low-order diffraction light (first-order diffraction light) and relatively high-order diffraction light (second-order diffraction light) interfere within the target area (TA) of the photoresist (PR). The interference pattern formed in this way can have improved resolution compared to an interference pattern formed only with relatively low-order diffraction light (first-order diffraction light) as in conventional EUV interference lithography technology.

[0107] More specifically, the interference pattern formed on the photolithography (PR) by relatively low-order diffraction light (1st-order diffraction light) has a period of p1 according to the above <Mathematical Formula 3>, and the interference pattern formed on the photolithography (PR) by relatively high-order diffraction light (2nd-order diffraction light) has a period of p2 according to the above <Mathematical Formula 4>, wherein p2 may have a value twice higher than p1. For example, the interference pattern formed on the photolithography (PR) by relatively low-order diffraction light (1st-order diffraction light) may appear like P1 illustrated in FIG. 7, and the interference pattern formed on the photolithography (PR) by relatively high-order diffraction light (2nd-order diffraction light) may appear like P2 illustrated in FIG. 7.

[0108] In other words, the interference pattern formed through the EUV interference lithography system according to the first embodiment may be formed by an interference pattern (P1) having a frequency of the p1 cycle and an interference pattern (P2) having a frequency of the p2 cycle that is twice as high as the p1 cycle interfering with each other (P1+P2). In this case, the interference pattern (P1+P2) may have an improved NILS (Normalized image log slope) compared to the interference pattern (P1) having a frequency of the p1 cycle, so that the point spread function is suppressed, and the distinction between two consecutive lines of the interference pattern becomes clear, so that the resolution can be improved.

[0109] The NILS value can be calculated using the <Mathematical Equation 5> below, and can be defined as a normalized value obtained by multiplying the log slope value of the light intensity at the pattern edge by the target line width. A higher NILS value may indicate a steeper slope of the light intensity distribution at the pattern edge.

[0110] <Mathematical Formula 5>

[0111]

[0112] (w: pitch size of interference pattern, I: intensity of interference pattern, x: spatial coordinate system)

[0113] That is, NILS is the intensity log slope at the position w where the size of the interference pattern is determined, and can be used as an indicator to evaluate process capability without performing an exposure process on the photoresist.

[0114] In Fig. 8, w1 denotes the pitch size of the interference pattern (P1) having the frequency of the p1 cycle, and w2 denotes the pitch size of the interference pattern (P1+P2) in which the frequency of the p1 cycle and the frequency of the p2 cycle interfere. As can be seen in Fig. 8, it can be seen that the NILS value of the interference pattern in which the frequency of the p1 cycle and the frequency of the p2 cycle interfere (the interference pattern formed by the EUV interference lithography system according to the first embodiment) is improved compared to the interference pattern in which the frequency of the p1 cycle and the frequency of the p2 cycle interfere (the interference pattern formed by the EUV interference lithography system according to the first embodiment).

[0115]

[0116] EUV interference lithography system according to the second embodiment

[0117] FIG. 9 is a drawing for explaining an EUV interference lithography system according to a second embodiment of the present invention, and FIG. 10 is a drawing for explaining first to fourth pattern areas of a transmission mask used in an EUV interference lithography system according to a second embodiment of the present invention.

[0118] Referring to FIGS. 9 and 10, a transmissive mask (100) included in an EUV interference lithography system according to the second embodiment includes a membrane (110) including silicon nitride (SiN), and a pattern layer (120) disposed on the membrane (110) and including molybdenum (Mo), wherein the pattern layer (120) may include first to fourth pattern regions (P1, P2, P3, P4). According to one embodiment, the first to fourth pattern regions (P1, P2, P3, P4) may be defined as different regions each including a plurality of patterns.

[0119] According to one embodiment, the first pattern region (P1) and the second pattern region (P2) are pattern regions arranged adjacent to the central portion of the transmissive mask (100), and may be arranged to be spaced apart from each other by a first distance (D1). More specifically, the first distance (D1) may be defined as the distance between the central portion of the first pattern region (P1) and the central portion of the second pattern region (P2).

[0120] In contrast, the third pattern area (P3) and the fourth pattern area (P4) are pattern areas arranged adjacent to the outer portion of the transparent mask (100), and may be arranged to be spaced apart from each other by a second distance (D2). More specifically, the second distance (D2) may be defined as the distance between the center portion of the third pattern area (P3) and the center portion of the fourth pattern area (P4). In addition, the second distance (D2) may be longer than the first distance (D1).

[0121] That is, the transparent mask (100) may be arranged so that the first pattern area (P1) and the second pattern area (P1) are spaced apart from each other by the first distance (D1) in the central portion, and the third pattern area (P3) and the fourth pattern area (P4) are spaced apart from each other by the second distance (D2) with the first pattern area (P1) and the second pattern area (P2) interposed therebetween.

[0122] In addition, as illustrated in FIG. 10, the plurality of patterns within the first and second pattern areas (P1, P2) may have the same first pitch size (q1), while the plurality of patterns within the third and fourth pattern areas (P3, P4) may have the same second pitch size (q2). In addition, the second pitch size (q2) may be smaller than the first pitch size (q1). For example, the plurality of patterns within the first and second pattern areas (P1, P2) may have the first pitch size (q1) defined by the first line width (w1) and the first inter-pattern distance (d1), while the plurality of patterns within the third and fourth pattern areas (P3, P4) may have the second pitch size (q2) defined by the second line width (w2) narrower than the first line width (w1) and the second inter-pattern distance (d2) closer than the first inter-pattern distance (d1).

[0123] When EUV light (L) is irradiated onto the transmissive mask (100), a plurality of diffracted lights may be generated by transmitting and diffracting the EUV light (L) from the transmissive mask (100). According to one embodiment, first to fourth diffracted lights may be generated in each of the first to fourth pattern areas (P1, P2, P3, and P4). More specifically, a first diffracted light may be generated in the first pattern area (P1), a second diffracted light may be generated in the second pattern area (P2), a third diffracted light may be generated in the third pattern area (P3), and a fourth diffracted light may be generated in the fourth pattern area (P4). The first to fourth diffracted lights may interfere within the target area (TA) of the photoresist (PR) to form an interference pattern.

[0124] In one embodiment, the first to fourth diffracted lights may all include diffracted lights of the same order. More specifically, the first to fourth diffracted lights may all include first-order diffracted lights. For example, the first diffracted light may include -1-order diffracted light (DL1, -1 st ) and the second diffracted light is the +1st order diffracted light (DL1, +1 st ) and the third diffraction light is the -1st diffraction light (DL1, -1 st ) and the fourth diffracted light is +1st order diffracted light (DL1, +1 st ) may be included.

[0125] As described above, in order for the same order of diffracted light (first order diffracted light) generated in different pattern areas (first to fourth pattern areas) to interfere within the target area (TA), the second pitch size (q2) and the second distance (D2) can be controlled to have specific values. For example, the second pitch size (q2) can be controlled to have a value calculated through <Mathematical Expression 3> and <Mathematical Expression 6> below, and the second distance (D2) can be controlled to have a value calculated through <Mathematical Expression 7> below.

[0126] <Mathematical Formula 3>

[0127]

[0128] (p m : The period of the interference pattern formed on the photolithography by the m-th diffracted light, θ m : diffraction angle of m-th order diffracted light)

[0129] <Mathematical Formula 6>

[0130]

[0131] (q2: the second pitch size, m: diffracted light order, p m : Period of the interference pattern formed on the photolithography by the m-th diffracted light)

[0132] <Mathematical Formula 7>

[0133]

[0134] (D3: the second distance, H: the distance between the transparent mask and the photoresistor, θ diff : Diffraction angle of the third and fourth diffracted rays above)

[0135] According to one embodiment, the diffraction angles of the third and fourth diffracted light can be derived through <Mathematical Formula 2> described in the EUV interference lithography system according to the first embodiment.

[0136] The third and fourth diffracted lights include diffracted lights of the same order as the first and second diffracted lights, but since the distance (D2) between the third and fourth pattern regions is arranged to be greater than the distance (D1) between the first and second pattern regions, the diffraction angles of the third and fourth diffracted lights may be greater than the diffraction angles of the first and second diffracted lights.

[0137] When the second pitch size (q2) is controlled to have a value calculated through the above <Mathematical Formula 6> and the second distance (D2) is controlled to have a value calculated through the above <Mathematical Formula 7>, the interference pattern formed on the photolithography (PR) by the first and second diffracted lights may have a period of p1, while the interference pattern formed on the photolithography (PR) by the third and fourth diffracted lights may have a period of p2, which is twice as high as p1.

[0138] That is, the interference pattern formed through the interference lithography system according to the second embodiment may be formed by an interference pattern (P1) having a frequency of the p1 cycle and an interference pattern (P2) having a frequency of the p2 cycle that is twice as high as the p1 cycle interfering with each other (P1+P2). Accordingly, the interference pattern formed through the interference lithography system according to the second embodiment may also have improved resolution compared to an interference pattern formed through a conventional EUV interference lithography system.

[0139]

[0140] Fig. 11 is a drawing for explaining the process margin of the D value used in the EUV interference lithography system, and Fig. 12 is a drawing for explaining the process margin of the H value used in the EUV interference lithography system.

[0141] Referring to Fig. 11, the process margin of the D value means the D value at which each diffracted light can interfere, so the process margin of the D value for each diffracted light order is determined by the beam size of the diffracted light that contributes to the formation of the interference pattern, and the D error can cause a horizontal position error of the diffracted light. In addition, the process margin ΔD of the D value for each diffracted order is determined by the beam size of the m-th diffracted light. m The value is D m Since an error in the value occurs at the position where the m-th order diffracted light interferes with other diffracted light, the ±D value change can be considered. Accordingly, the process margin of the D value used in the EUV interference lithography system can be calculated to satisfy <Mathematical Formula 8> below.

[0142] <Mathematical Formula 8>

[0143]

[0144] (ΔD m : Process margin of D value by m-th diffracted light, BD m : beam size of m-th order diffracted light)

[0145] Referring to Fig. 12, the process margin of the H value means the H value at which each diffracted light can interfere, so the position shift (Δx) of the diffracted light according to the change in the H value in the H process margin by the diffraction order of the diffracted light forming the interference pattern may mean the H distance at which each diffracted light does not overlap. Accordingly, the process margin of the H value used in the EUV interference lithography system can be calculated to satisfy <Mathematical Formula 9> below. <Mathematical Formula 9> requires that the Δx distance according to the H error be shorter than the H process margin distance, and takes into account the ±H change.

[0146] <Equation 9>

[0147]

[0148] (ΔH: Process margin of H value, θ m : Diffraction angle of mth order diffracted light, BD m: beam size of m-th order diffracted light, Δx: positional displacement distance of diffracted light)

[0149]

[0150] While the present invention has been described in detail using preferred embodiments, the scope of the present invention is not limited to the specific embodiments described above, and should be interpreted in accordance with the appended claims. Furthermore, those skilled in the art will appreciate that numerous modifications and variations are possible without departing from the scope of the present invention.

[0151] The present invention can be used in the semiconductor industry.

Claims

1. In an EUV interference lithography system in which an interference pattern is formed on a photoresist by a plurality of diffracted lights transmitted and diffracted from a transmission mask, The above-mentioned transparent mask includes a first pattern region and a second pattern region spaced apart from each other by a first distance, a third pattern region and a fourth pattern region spaced apart from each other by a second distance greater than the first distance, with the first pattern region and the second pattern region interposed therebetween. An EUV interference lithography system, wherein a plurality of patterns within the first to fourth pattern areas have the same pitch size.

2. In paragraph 1, As EUV light is irradiated onto the transmissive mask, a first diffracted light is generated in the first pattern region, a second diffracted light is generated in the second pattern region, a third diffracted light is generated in the third pattern region, and a fourth diffracted light is generated in the fourth pattern region. An EUV interference lithography system in which the interference pattern is formed by interference of the first to fourth diffracted lights within a target area of ​​the photoresist.

3. In paragraph 2, An EUV interference lithography system wherein the first and second diffracted light rays include relatively low-order diffracted light rays, and the third and fourth diffracted light rays include relatively high-order diffracted light rays.

4. In paragraph 1, An EUV interference lithography system including the second distance calculated through <Mathematical Formula 1> and <Mathematical Formula 4> below. <Mathematical Formula 1> (H: distance between the above-mentioned transparent mask and the above-mentioned photoresist, D1: the first distance, θ1: diffraction angle of the first-order diffracted light) <Mathematical Formula 4> (D2: the second distance, H: the distance between the transmissive mask and the photoresistor, θ2: the diffraction angle of the second-order diffracted light) 5. In an EUV interference lithography system in which an interference pattern is formed on a photoresist by a plurality of diffracted lights transmitted and diffracted from a transmission mask, An EUV interference lithography system including a plurality of diffracted lights, wherein relatively low-order diffracted lights and relatively high-order diffracted lights are irradiated and interfered within a target area of ​​the photoresist to form the interference pattern.

6. In paragraph 5, Among the plurality of diffracted lights, the relatively low-order diffracted light is the diffracted light that is diffracted in the pattern area adjacent to the center of the transmissive mask and irradiated to the target area. An EUV interference lithography system including a diffracted light having a relatively high order among the plurality of diffracted lights, which is diffracted from a pattern area adjacent to the outer portion of the transmissive mask and irradiated to the target area.

7. In paragraph 5, An EUV interference lithography system including a diffraction angle of a relatively low-order diffracted light among the plurality of diffracted lights being smaller than a diffraction angle of a relatively high-order diffracted light among the plurality of diffracted lights.

8. In an EUV interference lithography system in which an interference pattern is formed on a photoresist by a plurality of diffracted lights transmitted and diffracted from a transmission mask, The above-mentioned transparent mask includes a first pattern region and a second pattern region spaced apart from each other by a first distance, a third pattern region and a fourth pattern region spaced apart from each other by a second distance greater than the first distance, with the first pattern region and the second pattern region interposed therebetween. An EUV interference lithography system, wherein a plurality of patterns within the first and second pattern areas have a first pitch size and a plurality of patterns within the third and fourth pattern areas have a second pitch size smaller than the first pitch size.

9. In paragraph 8, As EUV light is irradiated onto the transmissive mask, a first diffracted light is generated in the first pattern region, a second diffracted light is generated in the second pattern region, a third diffracted light is generated in the third pattern region, and a fourth diffracted light is generated in the fourth pattern region. An EUV interference lithography system in which the interference pattern is formed by interference of the first to fourth diffracted lights within a target area of ​​the photoresist.

10. In paragraph 9, An EUV interference lithography system wherein the first to fourth diffracted beams all include first-order diffracted beams.

11. In paragraph 9, An EUV interference lithography system including the second pitch size calculated through <Mathematical Formula 3> and <Mathematical Formula 6> below. <Mathematical Formula 3> (p m : The period of the interference pattern formed on the photolithography by the m-th diffracted light, θ m : diffraction angle of m-th order diffracted light) <Mathematical Formula 6> (q2: the second pitch size, m: diffracted light order, p m : Period of the interference pattern formed on the photolithography by the m-th diffracted light) 12. In paragraph 11, An EUV interference lithography system including the second distance calculated through the following <Mathematical Formula 7>. <Mathematical Formula 7> (D3: the second distance, H: the distance between the transparent mask and the photoresistor, θ diff : Diffraction angle of the third and fourth diffracted rays above) 13. In an EUV interference lithography system in which an interference pattern is formed on a photoresist by a plurality of diffracted lights transmitted and diffracted from a transmission mask, An EUV interference lithography system, comprising: a plurality of diffracted lights transmitted and diffracted in different pattern areas of the above-described transmission mask, wherein diffracted lights having the same order but different diffraction angles are irradiated and interfered within a target area of ​​the photoresist, thereby forming the interference pattern.

14. In paragraph 13, An EUV interference lithography system comprising a plurality of diffracted lights, wherein the diffracted light transmitted and diffracted in a pattern area having a relatively large pitch size and the diffracted light transmitted and diffracted in a pattern area having a relatively small pitch size interfere to form the interference pattern.

Images