Reverse photomask in which phase shift film pattern is used as reflection pattern and blank mask for making 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 shift film pattern is used as a reflective pattern, and a blank mask for fabricating the same. [Background technology]

[0002] Blank masks used in EUV lithography generally consist of two thin films on a substrate: a reflective film that reflects EUV light and an absorbing film that absorbs EUV light. Recently, phase-shift blank masks have been developed that can achieve higher resolution than binary blank masks with absorbing films. Phase-shift blank masks have a higher NILS (Normalized Image Log Slope) than binary blank masks, which can reduce stochastic defects caused by shot noise during wafer printing. Furthermore, phase-shift blank masks can achieve a low Dose to Space (DtS), thereby increasing semiconductor productivity.

[0003] 1 shows the basic structure of a phase shift blank mask for extreme ultraviolet lithography, which 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 shift film 108 formed on the capping film 105, and a resist film 120 formed on the phase shift film 108.

[0004] FIG. 2 shows a photomask fabricated using the blank mask of FIG. 1. After patterning the resist film 120 of the blank mask of FIG. 1, the patterned resist film 120 is used as an etching mask to pattern the phase shift film 108. The resist film 120 pattern is then removed, completing the fabrication of a photomask with a phase shift film pattern 108a and a reflective film pattern 104a. When EUV exposure light is incident on this photomask, the incident light that strikes the reflective film pattern 104a is reflected and irradiated onto the wafer, while a significant portion of the incident light that strikes the phase shift film pattern 108a is annihilated by destructive interference before being irradiated onto the wafer. The photoresist on the wafer is patterned due to the contrast difference of the reflected light irradiating the wafer.

[0005] 3 to 6 are views sequentially showing the process of patterning a wafer using the photomask of FIG. 2, and in particular, are views showing the process of patterning a wafer W using a positive photoresist (positive PR).

[0006] In the examples of Figures 3 to 6, for the sake of convenience of illustration and explanation, only the reflective film 104 and a portion of the phase shift film pattern 108a of the thin film of the photomask in Figure 2 are shown, and the incident light incident on the photomask is not shown, showing only the reflected light. In Figure 3, the protruding dots on the photomask for patterning, i.e., the phase shift film pattern 108a, are labeled d1, and the recessed portions, i.e., the holes where the phase shift film 108 has been removed to expose the reflective film 104, are labeled h1. In Figure 6, the protruding dots in the pattern after patterning of the wafer W is completed are labeled d2, and the recessed holes are labeled h2.

[0007] As shown in Figure 3, the 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 where the reflective film pattern 104a is formed and is blocked by the dot d1 where the phase shift film pattern 108a is formed. As the patterned reflected light is irradiated onto the wafer W, the areas of the positive resist exposed to the reflected light are removed, patterning the positive resist, as shown in Figure 4. The patterned positive resist is used as an etching mask to etch the wafer W as shown in Figure 5, and the positive photoresist is removed after etching is completed, resulting in a patterned wafer W as shown in Figure 6.

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

[0009] When a negative photoresist is used as shown in Figure 7, the areas of the negative photoresist exposed to reflected light remain, and the remaining areas are removed, as shown in Figure 8. The patterned negative photoresist is used as an etching mask to etch the wafer W as shown in Figure 9, and the negative photoresist is removed after etching is complete, resulting in a patterned wafer W as shown in Figure 10.

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

[0011] Generally, negative photoresists have the advantage of being thinner than positive photoresists and capable of forming fine patterns even at a low dose, and exhibit higher productivity and superior performance than positive photoresists. Therefore, a method of actively applying negative photoresists to wafers W is being considered. When negative photoresists are applied to wafers W, holes h1 in the photoresist form dots d2 on the wafer W, as described above.

[0012] However, the final exposure step among the exposure steps for fabricating a semiconductor device is always the step of forming holes h2 in the wafer W. This means that the step of forming dots d2 on the wafer W is always followed by one or more additional steps for forming holes h2. Therefore, a positive photoresist must be used in the final exposure step, and therefore, the reduced dose achieved by applying a negative photoresist in the previous exposure step does not directly translate into an increase in productivity in the overall process.

[0013] To apply a negative photoresist to the wafer W in the final exposure process, the dot d1 pattern of the photomask must be used to form the hole h2 on the wafer W. However, in this case, due to technical limitations in processing the photomask pattern, i.e., the phase shift film pattern 108a, it is impossible to reduce the pattern size to a level equivalent to the desired size of the hole h1. In addition, the exposure light reflected from the reflective film 104 may cause footing-type defects at the bottom of the pattern 108a, reducing the uniformity of the size of the hole h2 formed on the wafer W.

[0014] Due to these problems, the application of negative photoresists has been limited in actual wafer W patterning processes, despite the advantages of negative photoresists.

[0015] In the two examples described above, the holes h1 of the photomask were used as reflective patterns that reflect the exposure light, and the dots d1 were used as light-blocking patterns that block the exposure light. Research is currently underway to reverse this, where the exposure light is blocked in the areas on the wafer W corresponding to the holes h1 of the photomask, and the exposure light is irradiated in the areas on the wafer W corresponding to the dots d1 of the photomask. As a result, from the perspective of the wafer W, the holes h1 function as light-blocking patterns and the dots d1 function as reflective patterns. Photomasks of this type are hereinafter referred to as "reverse photomasks." 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. This allows for the advantages of negative photoresist to be obtained while eliminating all of the problems described above.

[0016] To fabricate such a reverse photomask, the blank mask used as the material for the photomask must have characteristics that are completely different from those of existing general blank masks. However, the structure of a blank mask for fabricating a reverse photomask has not been known to date. Summary of the Invention [Problem to be solved by the invention]

[0017] The present invention has been devised to solve the above problems, and its object is to provide a reverse photomask in which exposure light is blocked in areas on the wafer corresponding to the reflective film pattern of the photomask, and exposure light is irradiated in areas on the wafer corresponding to the phase shift film pattern of the photomask, so that from the wafer's perspective, the hole pattern of the photomask functions as a light-blocking pattern and the dot pattern functions as a reflective pattern.

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

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

[0020] A second aspect of the present invention relates to a reverse blank mask for extreme ultraviolet lithography, which comprises a substrate, a reflective film formed on the substrate, and a phase shift film formed on the reflective film, wherein the phase shift film has a relative reflectivity with respect to the reflective film of more than 15% for EUV exposure light having a wavelength of 13.5 nm and a thickness of less than 45 nm.

[0021] The reverse blank masks of the first and second aspects can be added or limited in various configurations as follows.

[0022] The phase shift film preferably has a relative reflectance of less than 35%.

[0023] The phase shift film preferably has a thickness of less than 35 nm, more preferably less than 30 nm.

[0024] The phase shift film may be configured to satisfy one of the following 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 formulas 1) to 5), the configuration may be such that any one of the following formulas 6) to 10) is satisfied.

[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 formulas 1) to 10), the ranges of the following 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 fabricated 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 fabricating 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 reflective film pattern act as a reflection pattern and a light shielding pattern for EUV incident light, respectively, and a blank mask used for fabricating 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, the advantages of the negative photoresist can be obtained, and the problems when using an existing photomask can be solved.

Brief Description of the Drawings

[0032] [Figure 1]1 is a diagram showing the basic structure of a conventional phase shift blank mask for extreme ultraviolet lithography. [Figure 2] FIG. 2 is a diagram showing a photomask produced using the blank mask of FIG. 1. [Figure 3] 3A to 3C are diagrams sequentially illustrating a process of patterning a wafer to which a positive photoresist is applied using the photomask of FIG. 2. [Figure 4] 3A to 3C are diagrams sequentially illustrating a process of patterning a wafer to which a positive photoresist is applied using the photomask of FIG. 2. [Figure 5] 3A to 3C are diagrams sequentially illustrating a process of patterning a wafer to which a positive photoresist is applied using the photomask of FIG. 2. [Figure 6] 3A to 3C are diagrams sequentially illustrating a process of patterning a wafer to which a positive photoresist is applied using the photomask of FIG. 2. [Figure 7] 3A to 3C are diagrams sequentially illustrating a process of patterning a wafer to which a negative photoresist is applied using the photomask of FIG. 2. [Figure 8] 3A to 3C are diagrams sequentially illustrating a process of patterning a wafer to which a negative photoresist is applied using the photomask of FIG. 2. [Figure 9] 3A to 3C are diagrams sequentially illustrating a process of patterning a wafer to which a negative photoresist is applied using the photomask of FIG. 2. [Figure 10] 3A to 3C are diagrams sequentially illustrating a process of patterning a wafer to which a negative photoresist is applied using the photomask of FIG. 2. [Figure 11] FIG. 1 shows a blank mask for fabricating a reverse photomask according to the present invention. [Figure 12] FIG. 12 is a diagram showing a photomask produced using the blank mask of FIG. [Figure 13] FIG. 10 is a diagram illustrating diffraction of reflected light. [Figure 14]13 is a diagram showing changes in the intensity of light generated in each region of the wafer by reflected light and diffracted light from the photomask of FIG. 12. FIG. [Figure 15] 1 is a graph showing the physical properties required for a phase shift film for realizing the reverse blank mask of the present invention as ranges related to the refractive index (n) and extinction coefficient (k) for EUV exposure light for each reflectance range. [Figure 16] 1 is a graph showing the physical properties required for a phase shift film for realizing the reverse blank mask of the present invention as ranges related to the refractive index (n) and extinction coefficient (k) for EUV exposure light for each reflectance range. [Figure 17] 1 is a graph showing the physical properties required for a phase shift film for realizing the reverse blank mask of the present invention as ranges related to the refractive index (n) and extinction coefficient (k) for EUV exposure light for each reflectance range. [Figure 18] 1 is a graph showing the physical properties required for a phase shift film for realizing the reverse blank mask of the present invention as ranges related to the refractive index (n) and extinction coefficient (k) for EUV exposure light for each reflectance range. [Figure 19] 1 is a graph showing the physical properties required for a phase shift film for realizing the reverse blank mask of the present invention as ranges related to the refractive index (n) and extinction coefficient (k) for EUV exposure light for each reflectance range. [Figure 20] 16 is a graph showing a range that is reduced compared to the ranges shown in FIG. 15. [Figure 21] 17 is a graph showing a range that is reduced compared to the ranges shown in FIG. 16. [Figure 22] 18 is a graph showing a range that is reduced compared to the ranges shown in FIG. 17. [Figure 23] 19 is a graph showing a range that is reduced compared to the ranges shown in FIG. 18. [Figure 24] 20 is a graph showing a range that is reduced compared to the ranges shown in FIG. 19. [Figure 25]3A to 3C are views sequentially illustrating a process of patterning a wafer to which a positive photoresist is applied using a reverse photomask according to the present invention. [Figure 26] 3A to 3C are views sequentially illustrating a process of patterning a wafer to which a positive photoresist is applied using a reverse photomask according to the present invention. [Figure 27] 3A to 3C are views sequentially illustrating a process of patterning a wafer to which a positive photoresist is applied using a reverse photomask according to the present invention. [Figure 28] 3A to 3C are views sequentially illustrating a process of patterning a wafer to which a positive photoresist is applied using a reverse photomask according to the present invention. [Figure 29] 3A to 3C are views sequentially illustrating a process of patterning a wafer to which a negative photoresist is applied using a reverse photomask according to the present invention. [Figure 30] 3A to 3C are views sequentially illustrating a process of patterning a wafer to which a negative photoresist is applied using a reverse photomask according to the present invention. [Figure 31] 3A to 3C are views sequentially illustrating a process of patterning a wafer to which a negative photoresist is applied using a reverse photomask according to the present invention. [Figure 32] 3A to 3C are views sequentially illustrating a process of patterning a wafer to which a negative photoresist is applied using a reverse photomask according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention will now be described in more detail with reference to the drawings.

[0034] 11 and 12 are diagrams showing a reverse blank mask and a reverse photomask, respectively, according to the present invention. The blank mask and photomask according to the present invention have the same basic configuration as the blank mask and photomask of the prior art described with reference to FIGS. 1 and 2. Therefore, in the following description of the present invention, the basic configurations of the blank mask and photomask will be briefly described, and the description of the blank mask and photomask of the prior art 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 shift film 208 formed on the capping film 205, and a resist film 220 formed on the phase shift film 208. A photomask is fabricated using such a blank mask. The photomask of Fig. 12 has a phase shift film pattern 208a and a reflective film pattern 204a patterned using a resist film 120.

[0036] On the other hand, if other thin films, such as an etch stop film or a hard mask film, remain on and / or under the specific thin film that performs the main phase shifting function and have the same pattern as the phase shifting film pattern 208a, the entire thin film including this specific thin film and the other thin films performs the phase shifting function. Therefore, when there are multiple thin films that remain as patterns in the photomask and perform the phase shifting function, the phase shifting film 208 in the description of the present invention refers to the entire stacked structure of those thin films.

[0037] In the reverse photomask, the absolute reflectance of the phase shifting film pattern 208a is lower than that of the reflective film pattern 204a. Therefore, as with conventional photomasks, incident light entering the photomask is reflected by the reflective film pattern 204a and blocked by the phase shifting film pattern 208a. More precisely, because the reflectance of the phase shifting film pattern 208a is lower than that of the reflective film pattern 204a, a contrast difference occurs, and this contrast difference causes the incident light to be reflected after patterning. However, as will be described in detail below, in the reverse photomask of the present invention, the reflected light and its diffracted light interfere with each other on the path from the photomask to the wafer W. As a result, the reflected exposure light is blocked in the area on the wafer corresponding to the reflective film pattern 204a of the photomask, while the reflected exposure light is irradiated in the area on the wafer corresponding to the phase shifting film pattern 208a of the photomask. As a result, from the wafer's perspective, the hole pattern of the photomask functions as a light-shielding pattern, and the dot pattern of the photomask functions as a reflective pattern.

[0038] For the sake of convenience, in the following description of the reverse photomask of the present invention, the terms "phase shift film pattern" and "reflective pattern" are used as terms having the same meaning, and the terms "reflective film pattern" and "light-shielding pattern" are used as terms having the same meaning. Furthermore, names having the same meaning are referred to by the same reference numerals.

[0039] The following describes the principle by which the phase shifting film pattern 208a functions as a reflective pattern and the reflective film pattern 204a functions as a light-shielding pattern in the reverse photomask of the present invention.

[0040] The basic principle of a reverse photomask is to use the diffracted light reflected from one pattern (e.g., a dot pattern) on the photomask to cause destructive interference with the reflected light from another opposite pattern (e.g., a hole pattern).

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

[0042] When exposure light is reflected from a reflective surface, diffraction occurs in the reflected light. The reflected light along the main path of incident light is referred to as 0th-order diffracted light (D0), and the diffracted light that forms a diffraction angle (θ) with respect to the main path is referred to as 1st-order diffracted light (D1). Because diffraction occurs symmetrically throughout space, a symmetrical −1st-order diffracted light (−D1) exists for each 1st-order diffracted light (D1). Although not shown in FIG. 13, diffracted light exists that is symmetrical to the direction penetrating the page of FIG. 13 in both the direction penetrating the page and the direction penetrating the page in FIG. 13. That is, diffracted light occurs in all directions on the surface of the reflective surface. Although not shown in FIG. 13, there is also second-order diffracted light that is diffracted at a second-order diffraction angle (e.g., θ2) that exceeds the diffraction angle (θ), and thus nth-order diffracted light exists in this manner. In the explanation of the principles of the present invention that utilize diffraction, illustrations and explanations of nth-order diffracted light and −1st-order diffracted light (−D1) are omitted.

[0043] A reverse photomask induces destructive interference between the zeroth-order diffracted light and the first-order diffracted light by causing the first-order diffracted light reflected from the photomask to appear at a position that is an integer multiple of the half-pitch of the pattern, relative to the position where the zeroth-order diffracted light appears on the wafer W. Here, "appearance position" refers to the position where the intensity peak of the diffracted light occurs. This creates a reverse effect in which the reflectance of the reflective film pattern 204a on the wafer W, where the reflected light is irradiated, is lower than the reflectance of the phase shift film pattern 208a. In other words, the exposure light is blocked in areas on the wafer W corresponding to the photomask holes h1, while the exposure light is irradiated in areas on the wafer W corresponding to the photomask dots d1.

[0044] FIG. 14 is a diagram specifically illustrating this effect, showing the change in intensity of light diffracted when exposure light is reflected by the photomask of FIG. 12. FIG. 14 shows an enlarged view of three reflective patterns 208a-1, 208a-2, and 208a-3 among the reflective patterns 208a of FIG. 12. Two light-shielding patterns 204a-1 and 204a-2 are present between the three reflective patterns 208a-1, 208a-2, and 208a-3. For ease of explanation, the capping film 205 is not shown in FIG. 14. In FIG. 14, graphs (Rh, Rd) of the change in intensity of reflected light and diffracted light are shown, partitioned to correspond to the areas on the photomask where the patterns 208a-1, 208a-2, 208a-3, 204a-1, and 204a-2 are formed.

[0045] Rh is a graph showing the reflected light (zeroth-order diffracted light) and first-order diffracted light from the light-shielding patterns 204a-1 and 204a-2, where Rh-1 is a graph showing the zeroth-order diffracted light and first-order diffracted light from the left-side light-shielding pattern 204a-1 and Rh-2 is a graph showing the zeroth-order diffracted light and first-order diffracted light from the right-side light-shielding pattern 204a-2. Rd is a graph showing the reflected light (zeroth-order diffracted light) and first-order diffracted light from the reflection patterns 208a-1, 208a-2, and 208a-3, where Rd-1 is a graph showing the zeroth-order diffracted light and first-order diffracted light from the left-side reflection pattern 208a-1, Rd-2 is a graph showing the zeroth-order diffracted light and first-order diffracted light from the center reflection pattern 208a-2, and Rd-3 is a graph showing the zeroth-order diffracted light and first-order diffracted light from the right-side reflection pattern 208a-3.

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

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

[0048] The nth-order diffracted light (second-order or higher diffracted light) is not shown for each of the patterns 208a-1, 208a-2, 208a-3, 204a-1, and 204a-2. Because the magnitude of the nth-order diffracted light is very small, it has little effect on the destructive and constructive interference described below. Also, for ease of understanding, each graph (Rh, Rd) in FIG. 14 shows a phase difference of approximately π between each of the regions W1, W2, and W3 on the wafer W. However, this does not represent the absolute phase difference. The actual phase difference may differ from that shown in FIG. 14 under the assumption that the intensity of light irradiating one region (e.g., W2) is greater than the intensity of light irradiating the regions to the left and right (e.g., W1 and W2) due to destructive and constructive interference, as described below.

[0049] In the first graph Rh of Figure 14, Rh-1 shows the intensity change in each region of the wafer W when light reflected by the left-side light-shielding pattern 204a-1 is irradiated onto the wafer W. The zeroth-order diffracted light of the left-side light-shielding pattern 204a-1 has an intensity distribution that is strongest in the center of region W1 and becomes weaker toward the edge. In regions adjacent to region W1 (the region to the left of W1 and W2), intensity changes occur due to first-order diffracted light. The first-order diffracted light has a lower intensity than the zeroth-order diffracted light, and has a distribution that is strongest approximately in the center of each region and becomes weaker toward the edge. The first-order diffracted light has an opposite phase to that of the zeroth-order diffracted light.

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

[0051] The first-order diffracted light from Rh-1 diffracted to the right and the first-order diffracted light from Rh-2 diffracted to the left overlap in the W2 region, causing constructive interference. Therefore, the sum of the first-order diffracted lights in the W2 region is approximately twice the size of each of the first-order diffracted lights.

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

[0053] Rd-1 and Rd-3 represent the intensity changes in each region of the wafer W when the light reflected from the left-side reflection pattern 208a-1 and right-side reflection pattern 208a-3 regions is irradiated onto the wafer W. Rd-1 and Rd-3 have the same shape as Rd-2, with the zeroth-order diffracted light present in the left region of region W1 and the right region of region W3, respectively, and the first-order diffracted light present in regions W1 and W3, respectively. As a result, in region W1, the first-order diffracted light of Rd-1 and the first-order diffracted light of Rd-2 overlap and cause constructive interference, while in region W3, the first-order diffracted light of Rd-3 and the first-order diffracted light of Rd-2 overlap and cause constructive interference. Therefore, the sum of the first-order diffracted light in regions W1 and W3 is approximately twice the magnitude of each first-order diffracted light.

[0054] 14, the third graph, Rh+Rd, shows the distribution of light (combination of Rh and Rd) irradiated to each region W1, W2, and W3 of wafer W. In each region W1, W2, and W3, overlapping of Rh and Rd causes destructive interference, resulting in a higher intensity of light irradiated to region W2, corresponding to central reflection pattern 208a-2, than the intensity of light irradiated to regions W1 and W3, corresponding to light-shielding patterns 204a-1 and 204a-2 on either side of it. The phase of region W2 is opposite to that of regions W1 and W3.

[0055] Because the reflective film 204 has a higher absolute reflectivity than the phase shift film 208, the intensity of light directly reflected from the reflective film 208 is lower than that from the reflective film 204. Therefore, the intensity of light directly reflected from the reflective patterns 208a-1, 208a-2, and 208a-3 constituting Rd is generally lower than the intensity of light directly reflected from the light-shielding patterns 204a-1 and 204a-2 constituting Rh. However, due to the destructive and constructive interference described above, the intensity of the irradiated light combined with the zeroth-order diffracted light and the first-order diffracted light is greater in W2 than in W1 and W3. Therefore, the exposure light is blocked in areas W1 and W3 on the wafer W corresponding to the hole pattern (reflective film pattern 204a) on the photomask, and is reflected in area W2 on the wafer W corresponding to the dot pattern (phase shift film pattern 208a) on the photomask. More precisely, since the intensity of the irradiated light is greater at W2 than at W1 and W3, patterned exposure light having a contrast difference is irradiated onto the wafer W. This embodies the reverse photomask of the present invention.

[0056] On the other hand, the illustration and description of FIG. 14 have been given assuming that the reflective pattern 208a and the light-shielding pattern 204a are line-shaped patterns. As a result, FIG. 14 shows that the first-order diffracted light of each pattern 204a, 208a is generated in the left and right regions of the zeroth-order diffracted light generating region, respectively. However, if the light-shielding pattern 204a were a hole pattern rather than a line pattern (i.e., if the photomask in FIG. 14 is shown in a plan view and the light-shielding pattern 204a has a hole shape when viewed from above and below in FIG. 14), the light-shielding pattern 204a would be surrounded on all four sides by the reflective pattern 208a. In this state, Rd would include constructive interference from four first-order diffracted light beams instead of two. In this case, the magnitude of Rd in the W1 and W3 regions would increase by approximately 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 Figure 14. This further increases the contrast of the W1 and W3 regions relative to the W2 region.

[0057] A specific configuration of a reverse photomask based on the above principle will be described below.

[0058] To realize 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 must be 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 must be adjusted by the settings of the exposure apparatus used in the exposure process. For example, this requirement can be met by adjusting the focusing position by adjusting the distance between the photomask and the wafer W. Therefore, this is a factor that is reflected in the actual use of the photomask rather than a factor related to the specifications of the photomask. However, when using a general photomask, adjusting the distance between the photomask and the wafer W does not produce a reverse effect. Therefore, in order to use it as a reverse photomask, a blank mask must be manufactured according to the specifications described below.

[0059] To realize the reverse photomask of the present invention, destructive interference and constructive interference must occur effectively. To achieve this, the phase shift film 208 must have a high reflectivity to increase the intensity of diffracted light. According to research conducted by the inventors of the present invention, to realize a reverse photomask, the phase shift film 208 must have a reflectivity of at least 15%. However, the inventors of the present invention discovered that if the reflectivity is too high, it becomes difficult to realize the reverse function. The preferred reflectivity of the phase shift film 208 is less than 35%. Here, reflectivity refers to the reflectivity for EUV exposure light with a wavelength of 13.5 nm, and also refers to the relative reflectivity, which is the ratio of the absolute reflectivity of the phase shift film 208 to the absolute reflectivity of the reflective film 204.

[0060] On the other hand, conventional phase shift films must effectively generate destructive interference between light reflected from the top and bottom of the film, and therefore are set to have a phase shift of approximately 180°. Conventional phase shift films generally have a target phase shift within the range of 160° to 210°. However, the inventors of the present invention have discovered that a reverse photomask can be effectively realized with a phase shift film 208 having a phase shift in a range different from the phase shift required by conventional photomasks. Research by the inventors of the present invention has shown that a phase shift in the range of 150° to 220° does not effectively realize the reverse function, but a phase shift in the range of 110° to 150° or 220° to 250° effectively realizes the reverse function.

[0061] In order for the phase shift film 208 to have the reflectance and phase shift amount described above, the material that constitutes the phase shift film 208 must have an appropriate extinction coefficient (k) and an appropriate refractive index (n).

[0062] The appropriate reflectance can be set by adjusting the extinction coefficient (k) and thickness (t) of the phase shift film 208. However, in order for a photomask formed with a phase shift film 208 having a thickness and extinction coefficient (k) determined based on this, to satisfy the above-mentioned range of phase shift and to achieve maximum performance in aspects such as NILS and DtS, a refractive index (n) within an appropriate range is required. That is, to realize the desired reverse function, the phase shift film 208 must have an appropriate optical constant (Nn-ik). However, the refractive index (n) and extinction coefficient (k), which indicate the optical characteristics of a thin film, are each elements that make up the optical constant (N), which is the complex refractive index, and are not mutually independent in terms of achieving maximum performance of the phase shift film 208. The requirements for a phase shift film taking these various aspects into consideration must be expressed as a function that defines the relationship between k and n.

[0063] The inventors of the present invention discovered that the function defining the relationship between k and n for a phase shifter film for implementing a reverse function must vary depending on the range of target reflectance. That is, a phase shifter film 208 having a particular range of reflectance and a phase shifter film 208 having a different range of reflectance require different ranges of k and n values. Generally, reflectance must be embodied to meet the requirements of each exposure process. For example, one exposure process may require a reflectance of 20%, while another exposure process may require a reflectance of 25%. The phase shifter film 208 must be fabricated to have a reflectance that meets these requirements. When the required reflectance differs, the ranges of n and k of the phase shifter film 208 for implementing the reverse function will differ.

[0064] Considering these various aspects, it is preferable that the range of values ​​of n and k of the phase shift film 208 for realizing the reverse photomask of the present invention is determined as a different function for each reflectance range.

[0065] Figs. 15 to 19 are graphs showing 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 for each reflectance range. Figs. 15 to 19 respectively show the ranges of n and k values for which the reverse function is embodied for reflectance 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[[ID=!7]] 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 reflectance of the phase inversion film with respect to EUV exposure light having a wavelength of 13.5 nm, k: extinction coefficient of the phase shift film for EUV exposure light with a wavelength of 13.5 nm, n: Refractive index of the phase shift film for EUV exposure light with a wavelength of 13.5 nm) The above formula may be satisfied by using only materials within the above range, or by combining multiple materials outside this range so that the resulting compound satisfies the formula. Furthermore, the phase shifter 208 may be formed as a multi-layer structure containing a single material or multiple compounds outside this range, so that the effective optical constant (eff.N) of the entire phase shifter 208 satisfies the formula.

[0068] The effective optical constant (eff.N) for two layers 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 shifter 208 may further contain light element materials such as N, O, C, B, and H. The refractive index (n) and extinction coefficient (k) of the phase shifter 208 are determined by the presence or absence and amount of such light element materials. Therefore, by adjusting the respective amounts of metals and light elements contained in the phase shifter 208, it is possible to realize a phase shifter 208 having n and k values ​​within the above-mentioned ranges.

[0070] Meanwhile, to ensure high reflectivity of the phase shift film 208, it is preferable for the phase shift film 208 to have a thin thickness. Therefore, in the reverse photomask of the present invention, which pursues high reflectivity, the thickness of the phase shift film 208 is reduced compared to general phase shift films, thereby achieving the effect of reducing the 3D effect. When a material with a high refractive index (n) and a low extinction coefficient (k) is used, an effective reverse function that meets the above requirements can be realized even with a thickness as large as 60 nm. However, when the above-mentioned formula for R, n, and k values ​​proposed in the present invention is satisfied, the reverse function is more easily realized when the phase shift film 208 has a thickness of less than 45 nm, and in this case, the effect of reducing the 3D effect can be further achieved. The thickness of the phase shift film 208 is preferably less than 35 nm, and more preferably less than 30 nm. It is clear that the phase shift film 208 must be thicker than the minimum thickness required to function as a thin film for phase shifting.

[0071] Figures 20 to 24 are graphs showing ranges that are reduced compared to the ranges shown in Figures 15 to 19. It was confirmed that the performance of the reverse photomask of the present invention is superior in the somewhat reduced ranges shown in Figures 20 to 24. The mathematical formulas corresponding to each reflectance 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 formulas corresponding to each of FIGS. 20 to 24, the formula defining the lower limit of the k value is the same as the aforementioned formula for FIGS. 15 to 19, and the region allowed by the formula defining the upper limit of the k value is reduced compared to the aforementioned formula for FIGS. 15 to 19. When such a formula 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 formula. 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 15 to 19 and 20 to 24 must satisfy at least one of the conditions for the phase shift amount of phase shift film 208 and the conditions for the thickness of phase shift film 208. That is, the phase shift amount of phase shift film 208 must be 110° to 150° or 220° to 250°, and the thickness of phase shift film 208 must be 45 nm or less, preferably less than 35 nm, and more preferably less than 30 nm. However, the reverse photomask of the present invention can be fabricated even if only one of these two conditions is satisfied, and the performance of the reverse photomask of the present invention can be further guaranteed when both of these conditions are satisfied.

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

[0076] 25 to 28 are diagrams sequentially showing the process of patterning a wafer using a 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 shifting film pattern 208a ultimately functions as a reflective pattern for incident light, and the reflective film pattern 204a ultimately functions as a light-shielding pattern for incident light. In consideration of this, in order to clearly explain the patterning process of the reverse photomask from a conceptual perspective, Figures 25 to 28 show that incident light is reflected by the phase shifting film pattern 208a and is shielded by the reflective film pattern 204a.

[0078] When a positive photoresist is used as in Fig. 25, the areas of the positive photoresist exposed to reflected light are removed, while the remaining areas remain, as in Fig. 26. The patterned positive photoresist is used as an etching mask to etch the wafer W as in Fig. 27, and the positive photoresist is removed after etching is completed, thereby obtaining a patterned wafer W as in Fig. 28.

[0079] As can be seen from Figures 25 and 28, when a reverse photomask is used to pattern a wafer W employing a positive resist, holes h1 in the photomask form dots d2 on the wafer W, and dots d1 in the photomask form holes h2 on the wafer W.

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

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

[0082] As can be seen from Figures 29 and 32, when using a reverse photomask to pattern a wafer W that employs a negative resist, a hole h1 in the photomask forms a hole h2 in the wafer W, and a dot d1 in the photomask forms a dot d2 in the wafer W.

[0083] In this way, when performing an exposure process on a wafer using the reverse photomask according to the present invention, when patterning a wafer W using a positive resist, holes h1 in the photomask form dots d2 on the wafer W, and dots d1 on the photomask form holes h2 on the wafer W. Conversely, when patterning a wafer W using a negative resist, holes h1 in the photomask form holes h2 on the wafer W, and dots d1 on the photomask form dots d2 on the wafer W.

[0084] In other words, when a wafer W using a negative photoresist is exposed using a reverse photomask, the hole h1 and dot d1 of the photomask correspond to the hole h2 and dot d2 of the wafer W, respectively, so the pattern of the photomask is the same as the pattern of the wafer W. Therefore, if a reverse photomask is used, it is 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] Although the present invention has been specifically described above by way of the embodiments with reference to the drawings, the embodiments are merely used for the purpose of illustrating and explaining the present invention, and are not used for the purpose of limiting the meaning or the scope of the present invention as described in the claims. Therefore, a person skilled in the art of the present invention will understand that various modifications and equivalent embodiments are possible from the embodiments, and the true scope of protection of the present invention should be determined by the technical matters of the claims. [Explanation of symbols]

[0086] 102 Circuit Board 104 Reflective film 104a Reflective film pattern 105 Capping membrane 108 Phase Reversal Film 108a Phase shift film pattern 120 Resist film 202 Substrate 204 Reflective film 204a Reflective film pattern 204a-1 Left side shading pattern 204a-2 Right side shading pattern 205 Capping Film 208 Phase Inversion Film 208a Phase shift film pattern 208a-1 Left side reflection pattern 208a-2 Reflection pattern on the central side 208a-3 Right side reflection pattern 220 Resist film

Claims

1. a substrate, a reflective film formed on the substrate, and a phase shift film formed on the reflective film, the phase shift film has a relative reflectance with respect to the reflective film of more than 15% and less than 35% for EUV exposure light having a wavelength of 13.5 nm; a phase shift amount of the reflected light reflected from the phase shift film when the EUV exposure light is incident thereon is 110° to 150° or 220° to 250°; The phase shift film has 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 (R is the relative reflectance, k is the extinction coefficient, and n is the refractive index for the EUV exposure light.) 1. A reverse blank mask for extreme ultraviolet lithography, comprising:

2. A liquid crystal display device comprising: a substrate; a reflective film formed on the substrate; and a phase shift film formed on the reflective film, the phase shift film has a relative reflectance with respect to the reflective film of more than 15% and less than 35% for EUV exposure light having a wavelength of 13.5 nm; a phase shift amount of the reflected light reflected from the phase shift film when the EUV exposure light is incident thereon is 110° to 150° or 220° to 250°; The phase shift film has 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 <h2 style=";text-align:left;direction:ltr">15)1515%<R<17.5%、-0.3112n+0.3108<k<-0.7670n<h2 style=";text-align:left;direction:ltr"> ２ <h2 style=";text-align:left;direction:ltr"> 2018-02-24 (R is the relative reflectance, k is the extinction coefficient, and n is the refractive index for the EUV exposure light.) 1. A reverse blank mask for extreme ultraviolet lithography, comprising:

3. A liquid crystal display device comprising: a substrate; a reflective film formed on the substrate; and a phase shift film formed on the reflective film, the phase shift film has a relative reflectance with respect to the reflective film of more than 15% and less than 35% for EUV exposure light having a wavelength of 13.5 nm; a phase shift amount of the reflected light reflected from the phase shift film when the EUV exposure light is incident thereon is 110° to 150° or 220° to 250°; The phase shift film has 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 (R is the relative reflectance, k is the extinction coefficient, and n is the refractive index for the EUV exposure light.) 1. A reverse blank mask for extreme ultraviolet lithography, comprising:

4. 4. The reverse blank mask for extreme ultraviolet lithography according to claim 1, wherein the phase shift film has a thickness of less than 45 nm.

5. 4. The reverse blank mask for extreme ultraviolet lithography according to claim 1, wherein the phase shift film has a thickness of less than 35 nm.

6. 4. The reverse blank mask for extreme ultraviolet lithography according to claim 1, wherein the phase shift film has a thickness of less than 30 nm.

7. A reverse photomask for extreme ultraviolet lithography, produced using the blank mask according to any one of claims 1 to 3.

8. Fabricating a reverse photomask according to claim 7; exposing a wafer using the reverse photomask; A wafer exposure method comprising:

9. 9. The wafer exposure method according to claim 8, wherein a negative photoresist is used on the wafer in the exposure step.

10. a substrate, a reflective film formed on the substrate, and a phase shift film formed on the reflective film, The phase shift film has a relative reflectance of more than 15% and less than 35% with respect to the reflective film for EUV exposure light having a wavelength of 13.5 nm, and a thickness of less than 45 nm; The phase shift film has 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 (R is the relative reflectance, k is the extinction coefficient, and n is the refractive index for the EUV exposure light.) 1. A reverse blank mask for extreme ultraviolet lithography, comprising:

11. A liquid crystal display device comprising: a substrate; a reflective film formed on the substrate; and a phase shift film formed on the reflective film, The phase shift film has a relative reflectance of more than 15% and less than 35% with respect to the reflective film for EUV exposure light having a wavelength of 13.5 nm, and a thickness of less than 45 nm; The phase shift film has 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 <h2 style=";text-align:left;direction:ltr">15)1515%<R<17.5%、-0.3112n+0.3108<k<-0.7670n<h2 style=";text-align:left;direction:ltr"> ２ <h2 style=";text-align:left;direction:ltr"> 2018-02-24 (R is the relative reflectance, k is the extinction coefficient, and n is the refractive index for the EUV exposure light.) 1. A reverse blank mask for extreme ultraviolet lithography, comprising:

12. A liquid crystal display device comprising: a substrate; a reflective film formed on the substrate; and a phase shift film formed on the reflective film, The phase shift film has a relative reflectance of more than 15% and less than 35% with respect to the reflective film for EUV exposure light having a wavelength of 13.5 nm, and a thickness of less than 45 nm; The phase shift film has 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 (R is the relative reflectance, k is the extinction coefficient, and n is the refractive index for the EUV exposure light.) 1. A reverse blank mask for extreme ultraviolet lithography, comprising:

13. A reverse photomask for extreme ultraviolet lithography, produced using the blank mask according to any one of claims 10 to 12.

14. Fabricating a reverse photomask according to claim 13; exposing a wafer using the reverse photomask; A wafer exposure method comprising:

15. 15. The wafer exposure method according to claim 14, wherein a negative photoresist is used on the wafer in the exposure step.

Images