Reverse photomask that phase shift film pattern is used for reflective pattern, and blankmask for manufacturing the same

Abstract

To provide a reverse photomask which, from the wafer's perspective, functions as if the hole pattern of the photomask serves as a shading pattern and the dot pattern serves as a reflective pattern, and further to provide a blankmask usable for manufacturing such a reverse photomask.SOLUTION: A reverse blankmask comprises a reflective film 204 formed on a substrate, and a phase shift film formed on the reflective film. The phase shift film has a relative reflectivity with respect to the reflective film exceeding 15% for EUV exposure light at a wavelength of 13.5 nm, a phase shift amount of 110° to 150° or 220° to 250°, and a thickness of less than 45 nm.SELECTED DRAWING: Figure 29

Description

Technical Field

[0001] The present invention relates to a blank mask and a photomask, and more particularly, to a reverse photomask in which a phase inversion film pattern is used as a reflection pattern and a blank mask for manufacturing the same.

Background Art

[0002] A blank mask used in EUV lithography generally includes two thin films, a reflective film that reflects EUV light and an absorption film that absorbs EUV light, on a substrate. Recently, a phase inversion blank mask capable of achieving higher resolution than a binary blank mask having the above-described absorption film has been developed. The phase inversion blank mask has a higher NILS (Normalized Image Log Slope) than a binary blank mask, thereby reducing the probability of stochastic defects due to the shot noise effect during wafer printing. In addition, since the phase inversion blank mask can achieve a low Dose to Space (DtS), semiconductor productivity can be increased.

[0003] FIG. 1 is a diagram showing the basic structure of a phase inversion blank mask for extreme ultraviolet lithography. The phase inversion blank mask for extreme ultraviolet lithography includes a substrate 102, a reflective film 104 formed on the substrate 102, a capping film 105 formed on the reflective film 104, a phase inversion film 108 formed on the capping film 105, and a resist film 120 formed on the phase inversion film 108.

[0004] FIG. 2 is a diagram showing a photomask fabricated using the blank mask of FIG. 1. After patterning the resist film 120 of the blank mask of FIG. 1, the phase inversion film 108 is patterned using the patterned resist film 120 as an etching mask. Then, by removing the pattern of the resist film 120, the fabrication of the photomask in which the phase inversion film pattern 108a and the reflective film pattern 104a are formed is completed. When EUV exposure light is incident on such a photomask, the incident light incident on the reflective film pattern 104a is reflected and irradiates the wafer, and the incident light incident on the phase inversion film pattern 108a is weakened by interference and then irradiates the wafer after a considerable part disappears. The photoresist on the wafer is patterned by the contrast difference of the reflected light irradiated on the wafer.

[0005] FIGS. 3 to 6 are diagrams sequentially showing the process of patterning a wafer using the photomask of FIG. 2. In particular, it is a diagram showing the process of patterning a wafer W using a positive photoresist (positive PR).

[0006] In the examples of FIGS. 3 to 6, for convenience of illustration and description, only a part of the reflective film 104 and the phase inversion film pattern 108a among the thin films of the photomask of FIG. 2 is shown, and the incident light incident on the photomask is omitted in the illustration, and only the reflected light that is reflected is shown. In FIG. 3, the dot portion protruding for patterning on the photomask, that is, the phase inversion film pattern 108a is denoted as d1, and the recessed portion, that is, the hole portion where the phase inversion film 108 is removed and the reflective film 104 is exposed is denoted as h1. In FIG. 6, the dot portion protruding in the pattern after the patterning of the wafer W is completed is denoted as d2, and the recessed hole portion is denoted as h2.

[0007] As shown in FIG. 3, EUV exposure light is reflected from the photomask and irradiated onto the wafer W. At this time, the EUV exposure light is reflected from the hole h1 portion where the reflective film pattern 104a is formed and blocked by the dot d1 portion where the phase inversion film pattern 108a is formed. By irradiating the wafer W with the reflected light patterned in this way, as shown in FIG. 4, the region of the positive resist exposed to the reflected light is removed and the positive resist is patterned. Using the patterned positive resist as an etching mask, the wafer W is etched as shown in FIG. 5, and after the etching is completed, the positive photoresist is removed, whereby the wafer W patterned as shown in FIG. 6 is obtained.

[0008] FIGS. 7 to 10 are diagrams sequentially showing the process of patterning a wafer using the photomask of FIG. 2. In particular, they are diagrams showing the process of patterning a wafer W using a negative photoresist (negative PR).

[0009] When a negative photoresist is employed as shown in FIG. 7, as shown in FIG. 8, the region of the negative photoresist exposed to the reflected light remains and the remaining portion is removed. Using the patterned negative photoresist as an etching mask, the wafer W is etched as shown in FIG. 9, and after the etching is completed, the negative photoresist is removed, whereby the wafer W patterned as shown in FIG. 10 is obtained.

[0010] When performing an exposure process on a wafer using a general photomask, when patterning a wafer W using a positive resist, as shown in FIGS. 3 to 6, the hole h1 of the photomask forms a hole h2 in the wafer W, and the dot d1 of the photomask forms a dot d2 in the wafer W. Conversely, when patterning a wafer W using a negative resist, as shown in FIGS. 7 to 10, the hole h1 of the photomask forms a dot d2 in the wafer W, and the dot d1 of the photomask forms a hole h2 in the wafer W.

[0011] Generally, negative photoresist has the advantages of being thinner in thickness than positive photoresist and being able to form fine patterns even at a low dose. It has higher productivity and exhibits excellent performance compared to positive photoresist. Therefore, a plan to actively apply negative photoresist to wafer W is being considered. When applying negative photoresist to wafer W, as described above, hole h1 of the photoresist forms dot d2 on wafer W.

[0012] However, in the final exposure process among the exposure processes for manufacturing semiconductor elements, it is always a process of forming hole h2 in wafer W. This means that there is always one or more additional processes for forming hole h2 after the process of forming dot d2 on wafer W. Therefore, positive photoresist must be used in the final exposure process, and thus, the dose reduced by the application of negative photoresist in the previous exposure process does not directly lead to an increase in productivity in the entire process.

[0013] To apply negative photoresist to wafer W even in the final exposure process, the dot d1 pattern of the photomask must be used for forming hole h2 on wafer W. However, in this case, due to the technical limitations in the processing of the pattern of the photomask, that is, the phase inversion film pattern 108a, it is impossible to reduce the pattern size to the level equivalent to the required size of hole h1. Also, defects in the form of footing may be induced at the lower end of pattern 108a by the exposure light reflected from reflection film 104, and the uniformity of the size of hole h2 formed on wafer W decreases.

[0014] Due to these problems, despite the advantages of negative photoresist, the application of negative photoresist has been restricted in the actual patterning process of wafer W.

[0015] In the above two examples, among the patterns formed on the photomask, the hole h1 was used as a reflection pattern that reflects the exposure light, and the dot d1 was used as a light-blocking pattern that blocks the exposure light. Conversely, in the region on the wafer W corresponding to the hole h1 of the photomask, the exposure light is blocked, and in the region on the wafer W corresponding to the dot d1 of the photomask, the exposure light is irradiated. As a result, from the perspective of the wafer W, a method is under research in which the hole h1 functions as if it were a light-blocking pattern and the dot d1 functions as if it were a reflection pattern. Such a photomask is hereinafter referred to as a "reverse photomask". If the reverse photomask is used in the exposure process, when a negative photoresist is applied to the wafer W, the dot pattern of the photomask forms a dot pattern on the wafer W, and the hole pattern of the photomask forms a hole pattern on the wafer W. Therefore, the advantages of the negative photoresist can be obtained, and all the above-mentioned problems can be solved.

[0016] In order to fabricate such a reverse photomask, the characteristics of the blank mask that is the material of the photomask need to be completely different from those of existing general blank masks. However, to date, nothing is known about the configuration of the blank mask for fabricating a reverse photomask.

Summary of the Invention

Problems to be Solved by the Invention

[0017] The present invention was devised to solve the above problems, and the object of the present invention is to block the exposure light in the region on the wafer corresponding to the reflection film pattern of the photomask, and irradiate the exposure light in the region on the wafer corresponding to the phase inversion film pattern of the photomask. As a result, from the perspective of the wafer, a reverse photomask is provided in which the hole pattern of the photomask functions as if it were a light-blocking pattern and the dot pattern functions as if it were a reflection pattern.

[0018] Another object of the present invention is to provide a blank mask that can be used for manufacturing such a reverse photomask.

Means for Solving the Problems

[0019] The reverse blank mask for extreme ultraviolet lithography according to the first aspect of the present invention includes a substrate, a reflective film formed on the substrate, and a phase inversion film formed on the reflective film. The phase inversion film has a relative reflectance with respect to the reflective film exceeding 15% for EUV exposure light having a wavelength of 13.5 nm, and the amount of phase inversion of the reflected light reflected from the phase inversion film when the EUV exposure light is incident is 110° to 150° or 220° to 250°.

[0020] The reverse blank mask for extreme ultraviolet lithography according to the second aspect of the present invention includes a substrate, a reflective film formed on the substrate, and a phase inversion film formed on the reflective film. The phase inversion film has a relative reflectance with respect to the reflective film exceeding 15% for EUV exposure light having a wavelength of 13.5 nm, and is characterized by having a thickness of less than 45 nm.

[0021] For the reverse blank masks of the first and second aspects, various configurations as described below can be added or limited.

[0022] Preferably, the phase inversion film has a relative reflectance of less than 35%.

[0023] Preferably, the phase inversion film has a thickness of less than 35 nm, more preferably less than 30 nm.

[0024] The phase inversion film may be configured to satisfy one of the following mathematical formulas.

[0025] 1) 32.5% < R < 35%, -0.1275n + 0.1305 < k < -6.6692n 2 + 12.1540n - 5.5071 2) 27.5% < R < 32.5%, -0.1500n + 0.1530 < k < -6.0311n 2 + 10.9240n - 4.9149 3) 22.5% < R < 27.5%, -0.1875n + 0.1900 < k < -4.2609n 2 + 7.6028n - 3.3581 4) 17.5% < R < 22.5%, -0.2362n + 0.2376 < k < -2.5346n 2 + 4.3613n - 1.8379 5) 15% < R < 17.5%, -0.3112n + 0.3108 < k < -7.9010n 2 + 14.1850n - 6.3175 Here, R, k, and n respectively represent the relative reflectance, extinction coefficient, and refractive index with respect to the EUV exposure light.

[0026] As a more limited range compared to the above mathematical formulas 1) to 5), it may be configured to satisfy any one of the following mathematical formulas 6) to 10).

[0027] 6) 32.5% < R < 35%, -0.1275n + 0.1305 < k < -1.6193n 2 + 2.8439n - 1.2255 7) 27.5% < R < 32.5%, -0.1500n + 0.1530 < k < -1.3636n 2 + 2.3341n - 0.9713 8) 22.5% < R < 27.5%, -0.1875n + 0.1900 < k < -1.7045n 2 + 2.9001n - 1.2006 9) 17.5% < R < 22.5%, -0.2362n + 0.2376 < k < -0.9554n 2 + 1.4681n - 0.5146 10) 15% < R < 17.5%, -0.3112n + 0.3108 < k < -0.7670n 2 + 0.9870n - 0.2242 In addition to the ranges of the above mathematical formulas 1) to 10), the ranges of the following mathematical formulas 11) to 14) are also possible.

[0028] 11) 32.5% < R < 35%, n = 0.92 ± 0.01, -0.1275n + 0.1305 < k < 0.03 12) 27.5% < R < 32.5%, n = 0.89 ± 0.01 or n = 0.92 ± 0.01, -0.1500n + 0.1530 < k < 0.03 13) 22.5% < R < 27.5%, n = 0.92 ± 0.01, -0.1875n + 0.1900 < k < 0.03 14) 15% < R < 17.5%, n = 0.90 ± 0.01, -0.3112n + 0.3108 < k < 0.05 According to another aspect of the present invention, there is provided a reverse photomask for extreme ultraviolet lithography manufactured using a blank mask having the above-described configuration.

[0029] According to still another aspect of the present invention, there is provided a wafer exposure method characterized by including a step of manufacturing a reverse photomask using the blank mask as described above, and a step of exposing a wafer using the reverse photomask.

[0030] Preferably, a negative photoresist is employed for the wafer in the exposure step.

Advantages of the Invention

[0031] According to the present invention, there are provided a reverse photomask in which a phase inversion film pattern and a reflection film pattern act as a reflection pattern and a light shielding pattern for EUV incident light, respectively, and a blank mask used for manufacturing such a photomask. When such a photomask of the present invention is used for exposing a wafer to which a negative photoresist is applied, the hole pattern of the photoresist can be used to form the hole pattern of the wafer. Thereby, it is possible to obtain the advantages of the negative photoresist and solve the problems when using an existing photomask.

Brief Description of the Drawings

[0032]

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Mode for Carrying Out the Invention

[0033] Hereinafter, the present invention will be described more specifically with reference to the drawings.

[0034] Figures 11 and 12 are diagrams showing a reverse blank mask and a reverse photomask according to the present invention. The blank mask and the photomask according to the present invention have the same basic configuration as the prior art blank mask and photomask described with reference to FIGS. 1 and 2. Therefore, in the following description of the present invention, the basic configuration of the blank mask and the photomask will be briefly described, and the description of the prior art blank mask and photomask described with reference to FIGS. 1 and 2 will be incorporated into the description of the present invention.

[0035] As shown in FIG. 11, the blank mask of the present invention includes a substrate 202, a reflective film 204 formed on the substrate 202, a capping film 205 formed on the reflective film 204, a phase inversion film 208 formed on the capping film 205, and a resist film 220 formed on the phase inversion film 208. The photomask is manufactured using such a blank mask. The photomask in FIG. 12 has a phase inversion film pattern 208a and a reflective film pattern 204a patterned using the resist film 120.

[0036] On the other hand, when another thin film, such as an etching stop film or a hard mask film, remains on the upper and / or lower part of a specific thin film that mainly performs the phase inversion function and has the same pattern as the phase inversion film pattern 208a, the entire thin film including this specific thin film and the other thin film performs the phase inversion function. Therefore, when there are a plurality of thin films that remain as patterns in the photomask and perform the phase inversion function, in the description of the present invention, the phase inversion film 208 means the entire laminated structure of these thin films.

[0037] Even in the reverse photomask, the absolute reflectance of the phase inversion film pattern 208a is lower than that of the reflective film pattern 204a. Therefore, as in the conventional photomask, the incident light incident on the photomask is reflected by the reflective film pattern 204a and blocked by the phase inversion film pattern 208a. More precisely, since the reflectance of the phase inversion film pattern 208a is lower than that of the reflective film pattern 204a, a contrast difference occurs, and due to this contrast difference, the incident light is reflected after patterning. However, as will be described in detail later, in the reverse photomask of the present invention, in the path where the reflected light is reflected by the photomask and irradiates the wafer W, the reflected light and its diffracted light interfere with each other. As a result, in the region on the wafer corresponding to the reflective film pattern 204a of the photomask, the exposed light to be reflected is blocked, and in the region on the wafer corresponding to the phase inversion film pattern 208a of the photomask, the exposed light to be reflected is irradiated. As a result, from the perspective of the wafer, it is as if the hole pattern of the photomask functions as a light-blocking pattern and the dot pattern of the photomask functions as a reflective pattern.

[0038] For the convenience of explanation considering such points, in the following description of the reverse photomask of the present invention, the "phase inversion film pattern" and the "reflection pattern" are used as terms having the same meaning, and the "reflective film pattern" and the "light-blocking pattern" are used as terms having the same meaning. Also, names having the same meaning in this way are referred to with the same reference numerals.

[0039] Hereinafter, the principle in which the phase inversion film pattern 208a functions as a reflection pattern and the reflective film pattern 204a functions as a light-blocking pattern as described above in the reverse photomask of the present invention will be described.

[0040] The basic principle of the reverse photomask is to cause destructive interference between the reflected light of one pattern (for example, a dot pattern) in the photomask and the reflected light of the other opposite pattern (for example, a hole pattern) by using the diffracted light of the reflected light.

[0041] FIG. 13 is a diagram for explaining the diffraction of reflected light.

[0042] When exposure light is reflected from a certain reflecting surface, diffraction occurs in the reflected light. The reflected light in the main path where the incident light is reflected is defined as the 0th-order diffracted light (D0), and the diffracted light forming a diffraction angle (θ) with respect to the main path is defined as the 1st-order diffracted light (D1). Also, since diffraction occurs symmetrically throughout the space, for the 1st-order diffracted light (D1), there exists a symmetric -1st-order diffracted light (-D1). Although not shown in FIG. 13, there exist diffracted lights that are mutually symmetric in the direction entering and exiting through the plane of the paper of FIG. 13. That is, diffracted light occurs in all directions on the plane of the reflecting surface. Also, although not shown in FIG. 13, there exists a 2nd-order diffracted light diffracted at a 2nd-order diffraction angle (for example, θ2) exceeding the diffraction angle (θ), and in this way, nth-order diffracted light exists. In the explanation regarding the principle of the present invention that utilizes diffraction, the illustration and description of the nth-order diffracted light and the -1st-order diffracted light (-D1) are omitted.

[0043] The reverse photomask induces destructive interference between the 0th-order diffracted light and the 1st-order diffracted light by causing the 1st-order diffracted light of the exposure light reflected from the photomask to appear at a position separated by an integer multiple of the half-pitch of the pattern based on the appearance position of the 0th-order diffracted light on the wafer W. Here, the "appearance position" means the position where the intensity peak of the diffracted light occurs. By utilizing this, from the perspective of the wafer W irradiated with the reflected light, an inversion effect is achieved such that the reflectance at the reflective film pattern 204a is rather lower than the reflectance at the phase inversion film pattern 208a. That is, it is possible to obtain the effect that the exposure light is blocked in the region on the wafer W corresponding to the hole h1 of the photomask and the exposure light is irradiated in the region on the wafer W corresponding to the dot d1 of the photomask.

[0044] FIG. 14 is a diagram for specifically explaining such an effect, and is a diagram showing the intensity change of light diffracted during the reflection of exposure light by the photomask of FIG. 12. In FIG. 14, three reflection patterns 208a-1, 208a-2, 208a-3 among the reflection patterns 208a of FIG. 12 are shown enlarged. Between the three reflection patterns 208a-1, 208a-2, 208a-3, there are two light-shielding patterns 204a-1, 204a-2. In FIG. 14, the capping film 205 is not shown for convenience of explanation. In FIG. 14, each graph (Rh, Rd) of the intensity change of the reflected light and the diffracted light is partitioned and shown so as to correspond to the region where each pattern 208a-1, 208a-2, 208a-3, 204a-1, 204a-2 on the photomask is formed.

[0045] Rh is a graph showing the reflected light (0th-order diffracted light) and the 1st-order diffracted light in the light-shielding patterns 204a-1, 204a-2. Among them, Rh-1 is a graph showing the 0th-order diffracted light and the 1st-order diffracted light in the left light-shielding pattern 204a-1, and Rh-2 is a graph showing the 0th-order diffracted light and the 1st-order diffracted light in the right light-shielding pattern 204a-2. Also, Rd is a graph showing the reflected light (0th-order diffracted light) and the 1st-order diffracted light in the reflection patterns 208a-1, 208a-2, 208a-3. Among them, Rd-1 is a graph showing the 0th-order diffracted light and the 1st-order diffracted light in the left reflection pattern 208a-1, Rd-2 is a graph showing the 0th-order diffracted light and the 1st-order diffracted light in the central reflection pattern 208a-2, and Rd-3 is a graph showing the 0th-order diffracted light and the 1st-order diffracted light in the right reflection pattern 208a-3.

[0046] In FIG. 14, the regions W1, W2, W3 partitioned for each graph are not regions on the photomask, but regions on the wafer W corresponding to each region on the photomask. For example, the W2 region is a region on the wafer W corresponding to the region where the central reflection pattern 208a-2 of the photomask of FIG. 14 is formed, and the W1 and W3 regions are regions on the wafer W corresponding to the regions where the left light-shielding pattern 204a-1 and the right light-shielding pattern 204a-2 of the photomask of FIG. 14 are formed, respectively.

[0047] In each graph of Rh and Rd, the zero-order diffracted light exists in the area on the wafer W corresponding to the area where the pattern is formed, and the first-order diffracted light exists in the areas on the wafer W corresponding to the left and right sides of the area where the pattern is formed. For example, for the reflected light from the left light-shielding pattern 204a-1, the zero-order diffracted light exists in the W1 area, and the first-order diffracted light exists in the left area and the right area W2 of the W1 area, respectively. Similarly, for the reflected light from the central reflection pattern 208a-2, the zero-order diffracted light exists in the W2 area, and the first-order diffracted light exists in the left area W1 and the right area W3 of the W2 area, respectively.

[0048] For each of the patterns 208a-1, 208a-2, 208a-3, 204a-1, 204a-2, the illustration of the nth-order diffracted light of the second-order diffracted light or higher is omitted. Since the size of the nth-order diffracted light is very small, the influence on the destructive interference and constructive interference described below is negligible. Also, each graph (Rh, Rd) in FIG. 14 is assumed to have a phase difference of approximately π between each area W1, W2, W3 on the wafer W for the sake of understanding, but this does not indicate the absolute phase difference. As will be described later, the actual phase difference may be different from FIG. 14 on the premise that the intensity of the light irradiated to one of the areas (for example, W2) is greater than the intensity of the light irradiated to the areas on its left and right sides (for example, W1, W2) due to destructive interference and constructive interference.

[0049] In Rh, which is the first graph in FIG. 14, Rh-1 shows the intensity change in each area of the wafer W when the reflected light reflected by the left light-shielding pattern 204a-1 is irradiated onto the wafer W. The zero-order diffracted light of the left light-shielding pattern 204a-1 has an intensity distribution that is strongest in the central part of the area W1 and becomes weaker towards the edge part. In the areas adjacent to the area W1 (the left area of W1 and W2), an intensity change due to the first-order diffracted light occurs. The first-order diffracted light has a lower intensity than the zero-order diffracted light and has a distribution that is strongest in the central part of each area and becomes weaker towards the edge part. The first-order diffracted light has a phase opposite to that of the zero-order diffracted light.

[0050] Rh-2 shows the intensity change in each region of the wafer W when the reflected light reflected by the right light-shielding pattern 204a-2 is irradiated onto the wafer W. The zeroth-order diffracted light of the right light-shielding pattern 204a-2 has an intensity distribution that is strongest at the central part of the region W3 and becomes weaker toward the edge part. In the regions (W2 and the right region of W3) adjacent to the region W3, an intensity change due to the first-order diffracted light occurs. The first-order diffracted light has a lower intensity than the zeroth-order diffracted light and generally has a distribution that is strongest at the central part of each region and becomes weaker toward the edge part. The first-order diffracted light has a phase opposite to that of the zeroth-order diffracted light.

[0051] Among the first-order diffracted lights of Rh-1, the diffracted light in the right direction and the first-order diffracted light of Rh-2 in the left direction overlap in the W2 region and cause constructive interference. Therefore, the magnitude of the sum of the first-order diffracted lights in the W2 region is approximately twice the magnitude of each first-order diffracted light.

[0052] In Rd, which is the second graph in FIG. 14, Rd-2 shows the intensity change in each region W1, W2, W3 of the wafer W when the reflected light reflected by the central-side reflection pattern 208a-2 is irradiated onto the wafer W. The zeroth-order diffracted light of the central-side reflection pattern 208a-2 has an intensity distribution that is strongest at the central part of the region W2 and becomes weaker toward the edge part. In the regions W1 and W3 adjacent to the region W2, an intensity change due to the first-order diffracted light occurs. The first-order diffracted light has a lower intensity than the zeroth-order diffracted light and generally has a distribution that is strongest at the central part of each region and becomes weaker toward the edge part. The first-order diffracted light has a phase opposite to that of the zeroth-order diffracted light.

[0053] Rd-1 and Rd-3 respectively show the intensity change in each region of the wafer W when the reflected light reflected in the regions of the left reflection pattern 208a-1 and the right reflection pattern 208a-3 is irradiated onto the wafer W. Rd-1 and Rd-3 have the same shape as Rd-2. The zero-order diffracted light exists in the left region of the W1 region and the right region of the W3 region respectively, and the first-order diffracted light exists in the W1 region and the W3 region respectively. As a result, in the W1 region, the first-order diffracted light of Rd-1 and the first-order diffracted light of Rd-2 overlap and cause constructive interference, and in the W3 region, the first-order diffracted light of Rd-3 and the first-order diffracted light of Rd-2 overlap and cause constructive interference. Therefore, the magnitude of the sum of the first-order diffracted lights in the W1 and W3 regions is approximately twice the magnitude of each first-order diffracted light.

[0054] Rh+Rd, which is the third graph in FIG. 14, shows the distribution of the light (combination of Rh and Rd) irradiated onto each region W1, W2, W3 of the wafer W. In each region W1, W2, W3, destructive interference occurs due to the overlap of Rh and Rd. As a result, the intensity of the light irradiated onto the region W2 corresponding to the central reflection pattern 208a-2 is higher than the intensity of the light irradiated onto the regions W1, W3 corresponding to the light-shielding patterns 204a-1, 204a-2 on both sides thereof. The phase of the W2 region is opposite to that of the W1 and W3 regions.

[0055] Since the reflective film 204 has a higher absolute reflectance than the phase inversion film 208, the intensity of the light directly reflected by the phase inversion film 208 is lower than that of the reflective film 204. Therefore, the intensity of the light directly reflected by each reflection pattern 208a-1, 208a-2, 208a-3 constituting Rd is basically lower than the intensity of the light directly reflected by each light-shielding pattern 204a-1, 204a-2 constituting Rh. However, the intensity of the irradiation light combining the zero-order diffracted light and the first-order diffracted light becomes larger in W2 than in W1 and W3 as a result of the destructive interference and the constructive interference as described above. Therefore, the exposure light is blocked in the regions W1 and W3 on the wafer W corresponding to the hole pattern (reflective film pattern 204a) in the photomask, and the effect that the exposure light is reflected in the region W2 on the wafer W corresponding to the dot pattern (phase inversion film pattern 208a) in the photomask is obtained. More precisely, since the intensity of the irradiated light is larger in W2 than in W1 and W3, the patterned exposure light having a contrast difference is irradiated onto the wafer W. Thereby, the reverse photomask of the present invention is realized.

[0056] On the other hand, in the illustration of FIG. 14 and the description thereof, the case where the reflection pattern 208a and the light-shielding pattern 204a are linear patterns was taken up and described. As a result, in FIG. 14, it is shown that the first-order diffracted light of each pattern 204a, 208a is generated in the regions on the left and right sides of the zero-order diffracted light generation region, respectively. However, if the light-shielding pattern 204a is not a linear pattern but a hole pattern (that is, when the photomask of FIG. 14 is shown on a plane and the light-shielding pattern 204a has a hole shape when viewed from above to below in FIG. 14), the light-shielding pattern 204a will be surrounded by the reflection pattern 208a on all four sides. In this state, Rd will include constructive interference by four, rather than two, first-order diffracted lights. In this case, the magnitude of Rd in the W1 and W3 regions increases by about two times compared to the case of FIG. 14 due to the doubled constructive interference. Therefore, the effect of destructive interference on Rh in the W1 and W3 regions increases, and the magnitude of Rh+Rd in the W1 and W3 regions becomes smaller than that shown in FIG. 14. As a result, the contrast of the W1 and W3 regions compared to the W2 region further increases.

[0057] Hereinafter, the specific configuration of the reverse photomask based on the above principle will be described.

[0058] In order to embody the reverse photomask of the present invention, the distance between the position where diffracted light is generated and the position where reflected light is generated needs to match an integer multiple of the half pitch of the pattern to be formed on the wafer W, as described above. However, this is a factor that should be adjusted by the setting of the exposure apparatus that performs the exposure process. For example, the focusing position can be adjusted by adjusting the distance between the photomask and the wafer W to meet such requirements. Therefore, it can be said that this is a factor that is reflected during the actual use of the photomask rather than a factor for the specifications of the photomask. However, when using a general photomask, the reverse effect cannot be obtained even by adjusting the distance between the photomask and the wafer W. In order to be used as a reverse photomask, a blank mask needs to be fabricated with the specifications described below.

[0059] In order to embody the reverse photomask of the present invention, destructive interference and constructive interference need to be effectively generated. For this purpose, it is necessary to increase the intensity of the diffracted light by making the phase inversion film 208 have a high reflectivity. According to the research of the inventors of the present invention, in order to embody the reverse photomask, the phase inversion film 208 needs to have a reflectivity exceeding at least 15%. However, the inventors of the present invention have discovered that when the reflectivity is too high, it becomes difficult to embody the reverse function. The preferable reflectivity of the phase inversion film 208 is less than 35%. Here, the reflectivity means the reflectivity with respect to the EUV exposure light having a wavelength of 13.5 nm, and also means the relative reflectivity which is the ratio of the absolute reflectivity of the phase inversion film 208 to the absolute reflectivity of the reflection film 204.

[0060] On the other hand, the conventional phase inversion film must effectively generate destructive interference between the reflected lights reflected from the upper and lower parts of the phase inversion film, and thereby, the phase inversion amount is set to be around 180°. The target phase inversion amount of the conventional phase inversion film is generally set within the range of 160° to 210°. However, the inventors of the present invention have discovered that the reverse photomask can be effectively embodied in a range where the phase inversion amount of the phase inversion film 208 is different from the phase inversion amount pursued by a general photomask. According to the research of the inventors of the present invention, when the phase inversion amount is in the range of 150° to 220°, the reverse function cannot be effectively embodied, and when the phase inversion amount is in the range of 110° to 150° or 220° to 250°, the reverse function can be effectively embodied.

[0061] In order for the phase inversion film 208 to have the reflectivity and phase inversion amount as described above, the material constituting the phase inversion film 208 needs to have an appropriate extinction coefficient (k) and an appropriate refractive index (n).

[0062] The above-mentioned appropriate reflectance can be set by adjusting the extinction coefficient (k) and thickness (t) of the phase inversion film 208. However, in order for the photomask formed with the phase inversion film 208 having the thickness and extinction coefficient (k) determined in consideration of this to satisfy the above-mentioned range of phase inversion amount, and in order to have the maximum performance in terms of NILS and DtS, etc., an appropriate range of refractive index (n) is required. That is, for the realization of a preferable reverse function, the phase inversion film 208 must have appropriate optical constants (N = n - ik). However, the refractive index (n) and extinction coefficient (k) indicating the optical characteristics of the thin film are each element constituting the optical constant (N) which is a complex refractive index, and are not independent of each other from the viewpoint of expressing the maximum performance of the phase inversion film 208. The requirements for the phase inversion film considering such various aspects must be expressed as a function defining the relationship between k and n.

[0063] In addition, the inventors of the present invention have discovered that the function defining the mutual relationship between k and n for the phase inversion film for realizing the reverse function needs to change depending on the range of the target reflectance. That is, the phase inversion film 208 having a reflectance in a specific range and the phase inversion film 208 having a reflectance in a different range require different ranges of k and n values. On the other hand, generally, the reflectance needs to be realized to meet the requirements in individual exposure processes. For example, in a certain exposure process, a reflectance of 20% may be required, and in another exposure process, a reflectance of 25% may be required. The phase inversion film 208 needs to be manufactured to have a reflectance that meets such requirements. When the required reflectances are different in this way, the ranges of n and k of the phase inversion film 208 for realizing the reverse function will be different.

[0064] When considering such various aspects, it is preferable that the ranges of the values of n and k of the phase inversion film 208 for realizing the reverse photomask of the present invention are determined as different functions for each reflectance range.

[0065] Figures 15 to 19 are graphs showing, for each reflectivity range, the physical properties required for the phase inversion film for embodying the reverse photomask of the present invention as ranges related to the refractive index (n) and extinction coefficient (k) with respect to EUV exposure light. Figures 15 to 19 respectively show the ranges of n and k values for which the reverse function is embodied for reflectivity ranges of 32.5 < R < 35%, 27.5 < R < 32.5%, 22.5 < R < 27.5%, 1.75 < R < 22.5%, and 15 < R < 17.5%. In this graph, the horizontal axis represents the refractive index (n) with respect to EUV exposure light having a wavelength of 13.5 nm, and the vertical axis represents the extinction coefficient (k) with respect to EUV exposure light having a wavelength of 13.5 nm. In each graph, the range surrounded by a straight line and a partial arc is the range in which the reverse photomask of the present invention can be embodied. Substances outside this range are difficult to embody the reverse function, or even if they are embodied, it is difficult to satisfy other required performance specifications, such as DtS (Dose to Space) or NILS (Normalized Image Log Slope).

[0066] Each range in FIGS. 15 to 19 may be expressed by the following mathematical formulas.

[0067] 32.5% < R < 35%, -0.1275n + 0.1305 < k < -6.6692n 2 + 12.1540n - 5.5071 27.5% < R < 32.5%, -0.1500n + 0.1530 < k < -6.0311n 2 + 10.9240n - 4.9149 22.5% < R < 27.5%, -0.1875n + 0.1900 < k < -4.2609n 2 + 7.6028n - 3.3581 17.5% < R < 22.5%, -0.2362n + 0.2376 < k < -2.5346n 2 + 4.3613n - 1.8379 15% < R < 17.5%, -0.3112n + 0.3108 < k < -7.9010n 2 + 14.1850n - 6.3175 (R: Relative reflectivity of the phase inversion film with respect to EUV exposure light having a wavelength of 13.5 nm, k: extinction coefficient of the phase inversion film with respect to EUV exposure light having a wavelength of 13.5 nm n: refractive index of the phase inversion film with respect to EUV exposure light having a wavelength of 13.5 nm) The above formula may be satisfied by using only substances within the range as described above, or a plurality of substances outside this range may be combined so that the compound satisfies the above formula. Further, by forming a phase inversion film 208 having a multi-layer structure including one substance or a compound of a plurality of substances outside this range, the effective optical constant (eff.N) of the entire phase inversion film 208 may be made to satisfy the above formula.

[0068] When there are two layers, the effective optical constant (eff.N) is defined by the following formula.

[0069] eff.N=(n1×t1+n2×t2) / (t1+t2)-i(k1×t1+k2×t2) / (t1+t2) (n1,k1,t1: refractive index, extinction coefficient, thickness of the first layer, n2,k2,t2: refractive index, extinction coefficient, thickness of the second layer) In addition to metals, the phase inversion film 208 may further contain light element substances such as N, O, C, B, and H. The refractive index (n) and extinction coefficient (k) of the phase inversion film 208 are also determined by the presence or absence and content of such light element substances. Therefore, by adjusting the respective contents of the metal and light elements contained in the phase inversion film 208, a phase inversion film 208 having n and k values within the range described above can be realized.

[0070] On the other hand, in order to ensure a high reflectivity of the phase inversion film 208, the phase inversion film 208 preferably has a thin thickness. Therefore, in the reverse photomask of the present invention that pursues high reflectivity, the thickness of the phase inversion film 208 is reduced compared to a general phase inversion film, and thereby, the reverse photomask of the present invention can obtain an effect of reducing the 3D effect. When a substance having a high refractive index (n) and a low extinction coefficient (k) is used, for example, even with a thickness of 60 nm, an effective reverse function satisfying the above-described requirements can be realized. However, when the mathematical formulas of the above-described R, n, and k values presented in the present invention are satisfied, the reverse function is more easily realized when the phase inversion film 208 has a thickness of less than 45 nm, and in this case, the effect of further reducing the 3D effect can also be obtained. Note that the thickness of the phase inversion film 208 is preferably less than 35 nm, and more preferably less than 30 nm. It will be obvious that the phase inversion film 208 must be thicker than the minimum thickness for functioning as a thin film for phase inversion.

[0071] FIGS. 20 to 24 are graphs showing ranges reduced compared to the respective ranges shown in FIGS. 15 to 19. It was confirmed that the performance of the reverse photomask of the present invention is more excellent in the somewhat reduced ranges as shown in FIGS. 20 to 24. The mathematical formulas corresponding to the respective reflectivities shown in each figure are as follows.

[0072] 32.5% < R < 35%, -0.1275n + 0.1305 < k < -1.6193n 2 +2.8439n - 1.2255 27.5% < R < 32.5%, -0.1500n + 0.1530 < k < -1.3636n 2 +2.3341n - 0.9713 22.5% < R < 27.5%, -0.1875n + 0.1900 < k < -1.7045n 2 +2.9001n - 1.2006 17.5% < R < 22.5%, -0.2362n + 0.2376 < k < -0.9554n 2 +1.4681n - 0.5146 15% < R < 17.5%, -0.3112n + 0.3108 < k < -0.7670n 2 + 0.9870n - 0.2242 In the above equations corresponding to each of FIGS. 20 to 24, the equation defining the lower limit of the k value is the same as the aforementioned equation for FIGS. 15 to 19, and the region allowed by the equation defining the upper limit of the k value is reduced compared to the aforementioned equation for FIGS. 15 to 19. When such an equation is satisfied, the performance as a reverse photomask is more excellent, and the possibility of defects due to product-specific tolerances in the manufacturing process is reduced.

[0073] On the other hand, the inventor of the present invention discovered that there is a specific range in which the reverse photomask of the present invention can be manufactured even outside the range represented by the above equations. In FIGS. 20 to 22 and FIG. 24, such a specific range is indicated by dots at points outside the range indicated by the regions partitioned in each figure. For example, in FIG. 20, a position where n is about 0.92 and k is slightly smaller than about 0.03 is indicated. Such a specific range exists in 1 region in FIG. 20, 2 regions in FIG. 21, 1 region in FIG. 22, and 1 region in FIG. 24, and does not exist in FIG. 23. Expressing such a specific range in association with the reflectance range of each figure is as follows.

[0074] 32.5% < R < 35%, n = 0.92 ± 0.01, -0.1275n + 0.1305 < k < 0.03 27.5% < R < 32.5%, n = 0.89 ± 0.01 or n = 0.92 ± 0.01, -0.1500n + 0.1530 < k < 0.03 22.5% < R < 27.5%, n = 0.92 ± 0.01, -0.1875n + 0.1900 < k < 0.03 15% < R < 17.5%, n = 0.90 ± 0.01, -0.3112n + 0.3108 < k < 0.05 On the one hand, for the mathematical formulas for FIGS. 15 to 19 and the mathematical formulas for FIGS. 20 to 24 as described above, at least one of the conditions for the amount of phase inversion of the phase inversion film 208 and the conditions for the thickness of the phase inversion film 208 as described above of the present invention needs to be satisfied. That is, the amount of phase inversion of the phase inversion film 208 is required to be 110° to 150° or 220° to 250°, and the thickness of the phase inversion film 208 is required to be 45 nm or less, preferably less than 35 nm, and more preferably less than 30 nm. However, the production of the reverse photomask of the present invention is possible even if only one of these two conditions is satisfied, and when both of these conditions are satisfied, the performance of the reverse photomask of the present invention can be further guaranteed.

[0075] Hereinafter, the exposure process using the reverse photomask according to the present invention will be described.

[0076] FIGS. 25 to 28 are diagrams sequentially showing the process of patterning a wafer using the reverse photomask according to the present invention, and are diagrams showing the process of patterning a wafer W using a positive photoresist (positive PR).

[0077] As described above, in the reverse photomask of the present invention, the phase inversion film pattern 208a functions as a reflection pattern for incident light as a result, and the reflection film pattern 204a functions as a light shielding pattern for incident light as a result. In consideration of this, in FIGS. 25 to 28, in order to clearly explain the patterning process of the reverse photomask from a conceptual aspect, it is shown that incident light is reflected by the phase inversion film pattern 208a and incident light is shielded by the reflection film pattern 204a.

[0078] When a positive photoresist is employed as shown in FIG. 25, as shown in FIG. 26, the areas of the positive photoresist exposed to the reflected light are removed, and the remaining portions remain. Using the patterned positive photoresist as an etching mask, the wafer W is etched as shown in FIG. 27, and after the etching is completed, the positive photoresist is removed, thereby obtaining the patterned wafer W as shown in FIG. 28.

[0079] As can be seen from FIGS. 25 and 28, when patterning the wafer W using a positive resist with a reverse photomask, the hole h1 of the photomask forms a dot d2 on the wafer W, and the dot d1 of the photomask forms a hole h2 on the wafer W.

[0080] FIGS. 29 to 32 are diagrams sequentially showing the process of patterning a wafer using the reverse photomask according to the present invention, and are diagrams showing the process of patterning the wafer W on which a negative photoresist (negative PR) is employed.

[0081] When a negative photoresist is employed as shown in FIG. 29, as shown in FIG. 30, the areas of the negative photoresist exposed to the reflected light remain, and the remaining portions are removed. Using the patterned negative photoresist as an etching mask, the wafer W is etched as shown in FIG. 31, and after the etching is completed, the negative photoresist is removed, thereby obtaining the patterned wafer W as shown in FIG. 32.

[0082] As can be seen from FIGS. 29 and 32, when patterning the wafer W using a negative resist with a reverse photomask, the hole h1 of the photomask forms a hole h2 on the wafer W, and the dot d1 of the photomask forms a dot d2 on the wafer W.

[0083] Thus, when performing an exposure process on a wafer using the reverse photomask according to the present invention, when patterning a wafer W employing a positive resist, the hole h1 of the photomask forms a dot d2 on the wafer W, and the dot d1 of the photomask forms a hole h2 on the wafer W. Conversely, when patterning a wafer W employing a negative resist, the hole h1 of the photomask forms a hole h2 on the wafer W, and the dot d1 of the photomask forms a dot d2 on the wafer W.

[0084] In short, when exposing a wafer W employing a negative photoresist using a reverse photomask, since the hole h1 and the dot d1 of the photomask respectively correspond to the hole h2 and the dot d2 of the wafer W, the pattern of the photomask and the pattern of the wafer W become identical. Therefore, by using a reverse photomask, it becomes possible to apply a negative photoresist even when forming the hole h2 in the final exposure process of the overall exposure process for the wafer W.

[0085] Above, the present invention has been specifically described by way of embodiments of the present invention with reference to the drawings. However, the embodiments are merely used for the purpose of exemplifying and explaining the present invention, and are not used for meaning limitation or for limiting the scope of the present invention described in the claims. Therefore, those having ordinary knowledge in the technical field of the present invention can understand that various modifications and equivalent other embodiments are possible from the embodiments, and the true protection scope of the present invention should be determined by the technical matters in the claims.

Explanation of Reference Numerals

[0086] 102 Substrate 104 Reflective film 104a Reflective film pattern 105 Capping film 108 Phase inversion film 108a Phase inversion film pattern 120 Resist film 202 Substrate 204 Reflective film 204a Reflective film pattern 204a-1 Left side light-shielding pattern 204a-2 Right side light-shielding pattern 205 Capping film 208 Phase inversion film 208a Phase inversion film pattern 208a-1 Left side reflection pattern 208a-2 Central side reflection pattern 208a-3 Right side reflection pattern 220 Resist film

Claims

1. A reverse blank mask for extreme ultraviolet lithography, comprising a substrate, a reflective film formed on the substrate, and a phase inversion film formed on the reflective film, wherein the relative reflectance of the phase inversion film with respect to the reflective film exceeds 15% for EUV exposure light with a wavelength of 13.5 nm, and the amount of phase inversion of the reflected light reflected from the phase inversion film when the EUV exposure light is incident is 110° to 150° or 220° to 250°.

2. The reverse blank mask for extreme ultraviolet lithography according to claim 1, wherein the relative reflectance of the phase inversion film is less than 35%.

3. The phase inversion film satisfies any one of the following formulas (1) to (5): 1) 32.5% < R < 35%, -0.1275n + 0.1305 < k < -6.6692n ２ + 12.1540n - 5.5071 2) 27.5% < R < 32.5%, -0.1500n + 0.1530 < k < -6.0311n ２ + 10.9240n - 4.9149 3) 22.5% < R < 27.5%, -0.1875n + 0.1900 < k < -4.2609n ２ + 7.6028n - 3.3581 4) 17.5% < R < 22.5%, -0.2362n + 0.2376 < k < -2.5346n ２ + 4.3613n - 1.8379 5) 15% < R < 17.5%, -0.3112n + 0.3108 < k < -7.9010n ２ + 14.1850n - 6.3175 (For the EUV exposure light, R is the relative reflectance, k is the extinction coefficient, and n is the refractive index) The reverse blank mask for extreme ultraviolet lithography according to claim 2, wherein the phase inversion film satisfies any one of the above formulas.

4. The phase inversion film satisfies any one of the following formulas (6) to (10): 6) 32.5% < R < 35%, -0.1275n + 0.1305 < k < -1.6193n ２ + 2.8439n - 1.2255 7) 27.5% < R < 32.5%, -0.1500n + 0.1530 < k < -1.3636n ２ +2.3341n - 0.9713 8) 22.5% < R < 27.5%, -0.1875n + 0.1900 < k < -1.7045n ２ + 2.9001n - 1.2006 9) 17.5% < R < 22.5%, -0.2362n + 0.2376 < k < -0.9554n ２ +1.4681n - 0.5146 10) 15% < R < 17.5%, -0.3112n + 0.3108 < k < -0.7670n ２ + 0.9870n - 0.2242 (For the EUV exposure light, R is the relative reflectance, k is the extinction coefficient, and n is the refractive index) The reverse blank mask for extreme ultraviolet lithography according to claim 2, wherein the phase inversion film satisfies any one of the above formulas.

5. The phase inversion film satisfies any one of the following formulas (11) to (14): 11) 32.5% < R < 35%, n = 0.92 ± 0.01, -0.1275n + 0.1305 < k < 0.03 12) 27.5% < R < 32.5%, n = 0.89 ± 0.01 or n = 0.92 ± 0.01, -0.1500n + 0.1530 < k < 0.03 13) 22.5% < R < 27.5%, n = 0.92 ± 0.01, -0.1875n + 0.1900 < k < 0.03 14) 15% < R < 17.5%, n = 0.90 ± 0.01, -0.3112n + 0.3108 < k < 0.05 (For the EUV exposure light, R is the relative reflectance, k is the extinction coefficient, and n is the refractive index) The reverse blank mask for extreme ultraviolet lithography according to claim 2, wherein the phase inversion film satisfies any one of the above formulas.

6. The reverse blank mask for extreme ultraviolet lithography according to any one of claims 1 to 5, wherein the phase inversion film has a thickness of less than 45 nm.

7. The reverse blank mask for extreme ultraviolet lithography according to any one of claims 1 to 5, wherein the phase inversion film has a thickness of less than 35 nm.

8. The reverse blank mask for extreme ultraviolet lithography according to any one of claims 1 to 5, wherein the phase inversion film has a thickness of less than 30 nm.

9. A reverse photomask for extreme ultraviolet lithography, produced using the blank mask according to any one of claims 1 to 5.

10. A step of producing the reverse photomask according to claim 9, and A step of exposing a wafer using the reverse photomask, A wafer exposure method characterized by including.

11. The wafer exposure method according to claim 10, wherein a negative photoresist is employed for the wafer in the exposure step.

12. Including a substrate, a reflective film formed on the substrate, and a phase inversion film formed on the reflective film, The reverse blank mask for extreme ultraviolet lithography, wherein the phase inversion film has a relative reflectance with respect to the reflective film of more than 15% with respect to EUV exposure light having a wavelength of 13.5 nm and a thickness of less than 45 nm.

13. The reverse blank mask for extreme ultraviolet lithography according to claim 12, wherein the phase inversion film has a thickness of less than 35 nm.

14. The reverse blank mask for extreme ultraviolet lithography according to claim 12, wherein the phase inversion film has a thickness of less than 30 nm.

15. The reverse blank mask for extreme ultraviolet lithography according to any one of claims 12 to 14, wherein the relative reflectance of the phase inversion film is less than 35%.

16. The phase inversion film satisfies any one of the following formulas 1) to 5): 1) 32.5% < R < 35%, -0.1275n + 0.1305 < k < -6.6692n ２ + 12.1540n - 5.5071 2) 27.5% < R < 32.5%, -0.1500n + 0.1530 < k < -6.0311n ２ + 10.9240n - 4.9149 3) 22.5% < R < 27.5%, -0.1875n + 0.1900 < k < -4.2609n ２ + 7.6028n - 3.3581 4) 17.5% < R < 22.5%, -0.2362n + 0.2376 < k < -2.5346n ２ + 4.3613n - 1.8379 5) 15% < R < 17.5%, -0.3112n + 0.3108 < k < -7.9010n ２ + 14.1850n - 6.3175 (With respect to the EUV exposure light, R is the relative reflectance, k is the extinction coefficient, and n is the refractive index) The reverse blank mask for extreme ultraviolet lithography according to any one of claims 12 to 14, characterized by satisfying.

17. The phase inversion film satisfies any one of the following formulas 6) to 10): 6) 32.5% < R < 35%, -0.1275n + 0.1305 < k < -1.6193n ２ +2.8439n - 1.2255 7) 27.5% < R < 32.5%, -0.1500n + 0.1530 < k < -1.3636n ２ + 2.3341n - 0.9713 8) 22.5% < R < 27.5%, -0.1875n + 0.1900 < k < -1.7045n ２ + 2.9001n - 1.2006 9) 17.5% < R < 22.5%, -0.2362n + 0.2376 < k < -0.9554n ２ +1.4681n - 0.5146 10) 15% < R < 17.5%, -0.3112n + 0.3108 < k < -0.7670n ２ + 0.9870n - 0.2242 (With respect to the EUV exposure light, R is the relative reflectance, k is the extinction coefficient, and n is the refractive index) The reverse blank mask for extreme ultraviolet lithography according to any one of claims 12 to 14, characterized by satisfying.

18. The phase inversion film satisfies the following formulas 11) to 14): 11) 32.5% < R < 35%, n = 0.92 ± 0.01, -0.1275n + 0.1305 < k < 0.03 12) 27.5% < R < 32.5%, n = 0.89 ± 0.01 or n = 0.92 ± 0.01, -0.1500n + 0.1530 < k < 0.03 13) 22.5% < R < 27.5%, n = 0.92 ± 0.01, -0.1875n + 0.1900 < k < 0.03 14) 15% < R < 17.5%, n = 0.90 ± 0.01, -0.3112n + 0.3108 < k < 0.05 (For the EUV exposure light, R is the relative reflectance, k is the extinction coefficient, and n is the refractive index) The extreme ultraviolet lithography reverse blank mask according to any one of claims 12 to 14, characterized by satisfying any one of the above.

19. A reverse photomask for extreme ultraviolet lithography, fabricated using the blank mask according to any one of claims 12 to 14.

20. The step of fabricating the reverse photomask according to claim 19, The step of exposing a wafer using the reverse photomask, A wafer exposure method, characterized by including the above steps.

21. The wafer exposure method according to claim 20, characterized in that a negative photoresist is employed for the wafer in the exposure step.

Images