Photomask and exposure method

Abstract

To suppress dimensional shift errors caused by exposure. [Solution] The photomask of the embodiment includes a stitching region having a first end at one end and a second end at a predetermined distance inward from the first end, and comprises a substrate, a reflective layer disposed on the first surface of the substrate that reflects light, and a light-shielding pattern including a light-absorbing layer disposed on the second surface opposite to the substrate of the reflective layer that absorbs light, wherein the light reflection intensity in the stitching region is lower on the first end side than on the second end side.

Description

Technical Field

[0001] Embodiments of the present invention relate to a photomask and an exposure method.

Background Art

[0002] In High-NA EUV (High-Numerical Aperture Extreme Ultra-Violet) exposure, for a pattern transferred onto a wafer, the mask magnification is, for example, 4×8 times. On the other hand, the photomask itself is maintained at a size assuming a mask magnification of, for example, 4×4 times.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] One embodiment aims to provide a photomask and an exposure method capable of suppressing dimensional conversion differences that occur during exposure.

Means for Solving the Problems

[0005] The photomask of the embodiment includes a stitching region having a first end at one end and a second end at a predetermined distance inward from the first end, and comprises a substrate, a reflective layer disposed on the first surface of the substrate that reflects light, and a light-shielding pattern disposed on the second surface of the reflective layer opposite to the substrate that absorbs light, wherein the light reflection intensity in the stitching region is lower on the first end side than on the second end side. [Brief explanation of the drawing]

[0006] [Figure 1] A schematic diagram showing an example of the configuration of a photomask according to Embodiment 1. [Figure 2] A schematic diagram showing an example of the configuration of a light-shielding pattern provided on the wafer-facing surface of the photomask according to Embodiment 1. [Figure 3] A cross-sectional view illustrating, in order, a part of the procedure for the exposure method using a photomask according to Embodiment 1. [Figure 4] A cross-sectional view illustrating, in order, a part of the procedure for the exposure method using a photomask according to Embodiment 1. [Figure 5] A cross-sectional view illustrating a part of the procedure for the wafer processing method according to Embodiment 1. [Figure 6] A schematic diagram showing an example of the configuration of a light-shielding pattern provided on the wafer-facing surface of a photomask according to a modified example 1 of Embodiment 1. [Figure 7] A schematic diagram showing an example of the configuration of a photomask according to a modified example 2 of Embodiment 1. [Figure 8] A schematic diagram showing an example of the configuration of a photomask according to Embodiment 2. [Figure 9] A cross-sectional view illustrating, in sequence, a part of the manufacturing method of the pellicle according to Embodiment 2. [Figure 10] A cross-sectional view illustrating, in sequence, a part of the manufacturing method of the pellicle according to Embodiment 2. [Figure 11] A cross-sectional view illustrating, in sequence, a part of the method for manufacturing a pellicle according to a modified example 1 of Embodiment 2. [Figure 12]A cross-sectional view illustrating, in sequence, a part of the method for manufacturing a pellicle according to a modified example 1 of Embodiment 2. [Figure 13] A cross-sectional view illustrating, in sequence, a part of the method for manufacturing a pellicle according to a modified example 1 of Embodiment 2. [Figure 14] A cross-sectional view illustrating, in sequence, a part of the method for manufacturing a pellicle according to a modified example 1 of Embodiment 2. [Figure 15] A cross-sectional view illustrating, in sequence, a part of the method for manufacturing a pellicle according to a modified example 1 of Embodiment 2. [Figure 16] A cross-sectional view illustrating a part of the method for manufacturing a pellicle according to a modified example 2 of Embodiment 2. [Figure 17] A cross-sectional view illustrating, in sequence, a part of the method for manufacturing a pellicle according to a modified example 3 of Embodiment 2. [Figure 18] A cross-sectional view illustrating, in sequence, a part of the method for manufacturing a pellicle according to a modified example 3 of Embodiment 2. [Figure 19] A cross-sectional view illustrating, in sequence, a part of the method for manufacturing a pellicle according to a modified example 3 of Embodiment 2. [Figure 20] A schematic diagram showing an example of the configuration of a photomask according to modification 4 of Embodiment 2. [Modes for carrying out the invention]

[0007] Embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the embodiments described below. Furthermore, the components in the embodiments described below include those that are easily conceivable by those skilled in the art or that are substantially identical.

[0008] [Embodiment 1] Embodiment 1 will be described in detail below with reference to the drawings.

[0009] (Example of photomask configuration) FIG. 1 is a schematic diagram showing an example of the configuration of a photomask 10 according to Embodiment 1. More specifically, FIG. 1(a) is a cross-sectional view of the photomask 10 with a pellicle 20 attached, and FIGS. 1(b) and (c) are schematic diagrams showing an outline of an exposure method using the photomask 10.

[0010] In the following, even when simply described as the photomask 10 or the like, unless otherwise specified, it refers to the photomask 10 with the pellicle 20 attached, which will be described in detail below.

[0011] The photomask 10 of Embodiment 1 is configured as, for example, a reflective photomask used for high NA-EUV exposure.

[0012] High NA-EUV exposure is a technique in which, for example, exposure is performed with extreme ultraviolet light (EUV) of 13.5 nm using a lens whose numerical aperture (NA) has been expanded from 0.33 to 0.55. NA is a physical quantity indicating the performance of a lens that can converge and narrow light, and by using a high NA lens, finer pattern formation becomes possible.

[0013] Also, in high NA-EUV exposure, for the pattern transferred onto the wafer, for example, the mask magnification, which has been 4×4 times until now, becomes 4×8 times. Therefore, in order to maintain the previous mask size, for example, exposure to one shot region on the wafer is performed using two paired photomasks 10 (10-1, 10-⒉). The state is shown in FIGS. 1(b) and (c). [

[0014] As shown in FIG. 1(b), exposure is performed on approximately half of the region of the shot region SH provided on the wafer using one of the paired photomasks 10 (10-1, 10-⒉), the photomask 10-1.

[0015] As described above, the photomask 10 of Embodiment 1 is, for example, a reflective photomask, and the light L2, which is reflected from the light source LS such as EUV light L1, is irradiated onto the shot region SH. Although not shown in the figure, these lights L1 and L2 each reach the target photomask 10 or the shot region SH on the wafer via multiple reflectors.

[0016] As shown in Figure 1(c), the other photomask 10-2 of the pair of photomasks 10 (10-1, 10-2) is used to expose approximately half of the remaining shot region SH on the wafer.

[0017] Here, the exposure region EX1 by photomask 10-1 and the exposure region EX2 by photomask 10-2 partially overlap each other near the center of the shot region SH. Therefore, since this overlapping exposure region Dex is double-exposed, it is preferable to make some adjustments to prevent excessive light intensity due to double exposure. This is because excessive light intensity can lead to large dimensional differences in the exposure region Dex, such as the transfer pattern to the wafer becoming thinner.

[0018] Therefore, the photomask 10 is provided with a stitching region ST corresponding to the exposure region Dex, which adjusts for excessive light intensity in the exposure region Dex.

[0019] More specifically, in photomask 10-1, a stitching area ST is provided at the right edge E12-1 of the paper, corresponding to the vicinity of the center of the shot area SH, among the left and right edges E11-1 and E12-1 of the paper. In photomask 10-2, a stitching area ST is provided at the left edge E12-2 of the paper, corresponding to the vicinity of the center of the shot area SH, among the left and right edges E12-2 and E11-2 of the paper.

[0020] In these stitching regions ST, transfer patterns and the like that spanning the exposure regions EX1 and EX2 of the two photomasks 10 are joined together so that they are aligned with each other within the shot region SH.

[0021] As shown in Figure 1(a), the basic configuration of the pair of photomasks 10 may be common to each other.

[0022] The photomask 10 comprises a glass substrate 12 with one side covered by a conductive layer 11, and the other side of the glass substrate 12 faces the wafer side, and is held by an electrostatic chuck 30 of the exposure apparatus via the conductive layer 11. The glass substrate 12 is made of, for example, low thermal expansion glass (LTEML Low-Thermal-Expansion substrate Material).

[0023] Furthermore, the photomask 10 has a reflective layer 13, a buffer layer 14, and a light-absorbing layer 15 on the surface of the glass substrate 12 facing the wafer, in that order from the glass substrate 12 side.

[0024] The reflective layer 13 has a multilayer structure in which, for example, multiple Mo layers and multiple Si layers are alternately stacked one layer at a time. As a result, light such as exposure light incident on the reflective layer 13 at a predetermined angle undergoes diffraction and is reflected at an angle corresponding to the angle of incidence. Since it is difficult to reflect extremely short wavelength light such as EUV with optical mirrors, such an artificial lattice structure is used to reflect it.

[0025] The buffer layer 14 is, for example, a Ru layer and serves as the base layer for the light-absorbing layer 15. The light-absorbing layer 15 is, for example, a TaBN layer and has the property of absorbing exposure light such as EUV. The light-absorbing layer 15, together with the buffer layer 14, forms a light-shielding pattern P1 having a predetermined pattern and is dispersed on the reflective layer 13.

[0026] The light L1 from the light source LS is absorbed by the light absorption layer 15 of the light-shielding pattern P1, while the remaining light L2 is reflected back to the wafer by the reflective layer 13 exposed from the light-shielding pattern P1, thereby transferring the light-shielding pattern P1 to the shot region SH of the wafer.

[0027] Furthermore, as will be described later, the photomask 10 has a light-shielding pattern in the stitching region ST that is not transferred to the wafer.

[0028] The pellicle 20 comprises, for example, a protective layer 21 and a frame 22, and protects the surface on which the light-shielding pattern P1 of the photomask 10 is placed.

[0029] The protective layer 21 is, for example, a carbon-based layer such as carbon nanotubes or graphene, a resin layer such as polyimide, or an inorganic layer such as polysilicon or silicon carbide. When the protective layer 21 is a carbon-based layer, it is preferable that it is made of a material with a carbon content of 40% by mass or more. As a result, the protective layer 21 has high transmittance to exposure light such as EUV, and can cover and protect the surface of the photomask 10 with almost no obstruction to the incidence of light L1 from the light source LS to the photomask 10 and the emission of light L2 reflected from the photomask 10.

[0030] The frame 22 is made of, for example, an aluminum alloy and supports the protective layer 21. In the example shown in Figure 2(a), the frame 22 is held together with the photomask 10 by the electrostatic chuck 30 of the exposure apparatus, but the lower end of the frame 22 may be directly held to the surface of the photomask 10 by an adhesive or the like.

[0031] The pellicle 20 may also have an oxidation-suppressing layer (not shown) on the wafer-facing side of the protective layer 21 to suppress oxidation of the protective layer 21. In this case, for example, an SiO2 layer or a SiN layer can be used as the oxidation-suppressing layer.

[0032] Alternatively, the protective layer 21 alone, or the protective layer 21 with an oxidation-inhibiting layer, which is not attached to the frame 22, may be used as the pellicle.

[0033] A photomask 10 having the above configuration can be manufactured, for example, as follows.

[0034] A reflective layer 13 is formed on a glass substrate 12 by alternately stacking Mo layers and Si layers one at a time using chemical vapor deposition (CVD) or sputtering. A buffer layer 14 and a light-absorbing layer 15 are then formed on the reflective layer 13 in that order using CVD or sputtering, and processed into a pattern shape including a light-shielding pattern P1 using reactive ion etching (RIE). A conductive layer 11 is also formed on the back surface of the glass substrate 12 using CVD or sputtering.

[0035] The photomask 10 of Embodiment 1 is manufactured as described above.

[0036] Furthermore, the pellicle 20 having the above configuration can be manufactured, for example, as follows.

[0037] A protective layer 21 is formed on the support substrate using CVD or the like. If the protective layer 21 is a resin layer, it is also possible to form the protective layer 21 by immersing the support substrate in a dispersion liquid containing the resin material that will be the material for the protective layer 21. Alternatively, an oxidation-inhibiting layer covering the protective layer 21 may be further formed using CVD or the like. After that, the protective layer 21 is attached to the frame 22.

[0038] The pellicle 20 of Embodiment 1 is manufactured as described above.

[0039] Figure 2 is a schematic diagram showing an example of the configuration of light-shielding patterns P1 and P2 provided on the wafer-facing surface of the photomask 10 according to Embodiment 1. More specifically, Figure 2(a) is a plan view showing an example of the configuration of light-shielding patterns P1 and P2, and Figures 2(b) to (g) are plan views showing several examples of the configuration of light-shielding pattern P2.

[0040] As shown in Figure 2(a), the light-shielding pattern P1 is provided over substantially the entire surface of the photomask 10 facing the wafer, including the stitching area ST. The light-shielding pattern P1 is a pattern transferred to the wafer as described above, and a pattern based on the design pattern can be arbitrarily selected from various patterns such as line and space patterns, dot patterns, and hole patterns.

[0041] The light-shielding pattern P2, like the light-shielding pattern P1, is a pattern composed of a light-absorbing layer 15 and a buffer layer 14 provided on the reflective layer 13. However, while the light-shielding pattern P1 is transferred to the wafer in combination with the reflective layer 13, as described above, the light-shielding pattern P2 is not transferred to the wafer. The light-shielding pattern P2 may be, for example, an SRAF (Sub-Resolution Assist Feature) pattern.

[0042] More specifically, the light-shielding pattern P2 is positioned in the stitching region ST, and is configured such that the coverage increases in stages from end E31, which is one end of the stitching region ST, to end E32, which is the other end of the stitching region ST.

[0043] Here, the end E31 of the stitching region ST is the end closer to the center of the photomask 10. Also, the end E32 of the stitching region ST is located at the end E12 on one side of the photomask 10. In other words, the end E32 of the stitching region ST and the end E12 on one side of the photomask 10 coincide.

[0044] Several examples of light-shielding patterns P2 with varying coverage are shown in Figures 2(b) to 2(g).

[0045] In the examples shown in Figures 2(b) to 2(d), the shading patterns P21a to P21c, which are shading patterns P2, all have a line and space pattern.

[0046] As shown in Figure 2(b), the light-shielding pattern P21a is composed of lines, each having a constant width, and spaces whose width decreases towards the end E32 of the stitching region ST.

[0047] As shown in Figure 2(c), the light-shielding pattern P21b is composed of lines that increase in width toward the edge E32 of the stitching region ST, and spaces that each have a constant width.

[0048] As shown in Figure 2(d), the light-shielding pattern P21c is composed of lines that increase in width and spaces that decrease in width toward the edge E32 of the stitching region ST.

[0049] In the examples shown in Figures 2(e) to 2(g), the light-shielding patterns P22a to P22c, which are light-shielding patterns P2, all have a dot pattern.

[0050] As shown in Figure 2(e), the light-shielding pattern 22a has dots, each having a certain area, and these dots are arranged such that the pitch decreases towards the edge E32 of the stitching region ST.

[0051] As shown in Figure 2(f), the light-shielding pattern 22b has multiple dots of different areas, and these dots are arranged so that their area increases towards the edge E32 of the stitching region ST.

[0052] As shown in Figure 2(g), the light-shielding pattern 22c has multiple dots of different areas, and these dots are arranged such that the area increases and the pitch decreases towards the edge E32 of the stitching region ST.

[0053] In this way, the light-shielding pattern P2 can be constructed by combining predetermined patterns such as line and space patterns and dot patterns, and by changing either or both of the arrangement density (pitch) and size (width, area) of these patterns, the light-shielding pattern P2 can be configured such that the coverage of the stitching region ST increases in stages from the edge E31 to the edge E32.

[0054] By configuring the light-shielding pattern P2 such that the coverage rate changes within the stitching region ST, the amount of exposure light reflected from the photomask 10 to the wafer per unit area weakens as you approach the edge E12 on one side of the photomask 10. Therefore, it is possible to suppress the excess light intensity due to double exposure in the overlapping portion of the exposure regions EX1 and EX2 (see Figure 1(b) and (c)) of the two pair of photomasks 10, i.e., in the exposure region Dex.

[0055] With this configuration, the stitching region ST of the photomask 10 of Embodiment 1 has the function of adjusting the light-shielding pattern P1, etc., which are transferred to the exposure regions EX1, EX2, so that they are aligned with each other within the shot region SH.

[0056] In the above example, the case where the light-shielding pattern P2 has a line-and-space pattern or a dot pattern was described, but the light-shielding pattern P2 is not limited to these patterns. Any pattern can be adopted, such as a combination of a line-and-space pattern and a dot pattern, or other patterns, as long as the reflectivity of the photomask 10 per unit area can be adjusted.

[0057] Furthermore, the basic configuration of the paired photomasks 10 (10-1, 10-2) is common, as described above. However, this does not mean that each paired photomask 10 has the same light-shielding pattern P1 and the same light-shielding pattern P2.

[0058] Regarding the light-shielding pattern P1, each photomask 10 may have different light-shielding patterns P1 depending on the location of the corresponding shot region SH (see Figure 1(b) and (c)) of the wafer. For example, one of a pair of photomasks 10 may have a light-shielding pattern P1 corresponding to the element pattern, while the other has a light-shielding pattern P1 corresponding to the peripheral circuit pattern. On the other hand, in cases where repeating patterns occupy most of the shot region SH, such as in a large-capacity cell array, the pair of photomasks 10 may have identical light-shielding patterns P1.

[0059] Furthermore, with respect to the light-shielding pattern P2, each pair of photomasks 10 can adopt a light-shielding pattern P2 of any shape and arrangement. Each photomask 10 may be configured to have the same light-shielding pattern P2, or it may be configured to have different light-shielding patterns P2.

[0060] (Pattern formation method) Next, a pattern formation method including an exposure method using the photomask 10 of Embodiment 1 will be described with reference to Figures 3 to 5.

[0061] Figures 3 and 4 are cross-sectional views illustrating, in sequence, a part of the procedure for the exposure method using the photomask 10 according to Embodiment 1.

[0062] As shown in Figure 3(a), a wafer 100 is prepared in which the workpiece layer 110 and the photoresist layer 120 are formed in this order.

[0063] The wafer 100 is a semiconductor substrate, such as a silicon wafer. The layer to be processed 110 is a layer to be processed into a shape such as a light-shielding pattern P1, and can be an insulating layer such as an SiO2 layer or a SiN layer, a semiconductor layer such as a polysilicon layer, or a metal layer such as a tungsten layer. In the examples in Figures 3 to 5, the layer to be processed 110 is assumed to be an insulating layer such as an SiO2 layer. The photoresist layer 120 is the target of exposure using the photomask 10 and is a layer that serves as a mask when processing the layer to be processed 110.

[0064] Furthermore, the wafer 100 is assumed to be divided into multiple shot regions SH.

[0065] As shown in Figure 3(b), one of the pair of photomasks 10 (for example, photomask 10-1) is attached to the electrostatic chuck 30 of the exposure apparatus and placed in a predetermined position facing the wafer 100 that has been transported into the exposure apparatus. Light L1 such as EUV is irradiated onto the photomask 10 from the light source LS of the exposure apparatus (see Figures 1(b) and 1(c)) and reflected, and the reflected light L2 is irradiated onto the photoresist layer 120 of a predetermined shot region SH among a plurality of shot regions SH on the wafer 100.

[0066] As described above, in high NA-EUV exposure, the mask magnification is, for example, 4 × 8 times, and by combining the pair of photomasks 10, the entire shot region SH corresponding to a mask magnification of 4 × 8 times is exposed. Therefore, the photoresist layer 120 is exposed in approximately half of the shot region SH by the process shown in Figure 3(b). As described above, the region exposed by one of the photomasks 10 is called the exposed region EX1.

[0067] In the exposure region EX1, a pattern similar in shape to the light-shielding pattern P1 of one of the photomasks 10 is transferred to the photoresist layer 120. However, within the exposure region EX1, in the region corresponding to the stitching region ST of the photomask 10 (exposure region Dex), attenuated exposure light (light L2) is irradiated, so the degree of photosensitivity of the photoresist layer 120 may be lower than in other parts of the exposure region EX1.

[0068] As shown in Figure 4(a), the other of the pair of photomasks 10 (for example, photomask 10-2) is attached to the electrostatic chuck 30 of the exposure apparatus and placed in a predetermined position facing the wafer 100 inside the exposure apparatus. Light L1 such as EUV is irradiated onto the photomask 10 from the light source LS of the exposure apparatus (see Figures 1(b) and 1(c)) and reflected, and the reflected light L2 is irradiated onto the photoresist layer 120 of the shot region SH described above.

[0069] As a result, the photoresist layer 120 is exposed in approximately the remaining half of the shot area SH. As described above, the area exposed by the other photomask 10 is called the exposure area EX2.

[0070] In the exposure region EX2, a pattern similar in shape to the light-shielding pattern P1 of the other photomask 10 is transferred to the photoresist layer 120.

[0071] Furthermore, in the double-exposed exposure region Dex, where exposure regions EX1 and EX2 overlap, the amount of light per exposure is suppressed by the stitch region ST provided by each of the paired photomasks 10. As a result, after the second exposure, the accumulated amount of light becomes approximately equal to that of the other parts of exposure regions EX1 and EX2, and the degree of photosensitivity of the photoresist layer 120 also becomes approximately the same as that of the other parts.

[0072] As shown in Figure 4(b), by developing the photoresist layer 120 exposed using two photomasks 10, a resist pattern 120p is obtained in which the light-shielding pattern P1 of these photomasks 10 is transferred. Due to the stitching region ST function of the photomasks 10, the dimensional conversion difference of the resist pattern 120p is reduced even in the double-exposed exposure region Dex.

[0073] With the above steps, the exposure process using the photomask 10 of Embodiment 1 is completed.

[0074] From this point onward, the workpiece layer 110 on the wafer 100 is processed using the resist pattern 120p obtained by the post-exposure heat treatment and development.

[0075] Figure 5 is a cross-sectional view illustrating a part of the procedure for processing the wafer 100 according to Embodiment 1.

[0076] As shown in Figure 5(a), the workpiece layer 110 is processed using the resist pattern 120p as a mask, for example, by RIE, to form a workpiece layer 110t having, for example, multiple grooves TR.

[0077] As shown in Figure 5(b), the resist pattern 120p is removed by ashing using oxygen plasma or the like.

[0078] As shown in Figure 5(c), a conductive layer 130, such as a Cu layer, is filled into the groove TR of the workpiece layer 110. The conductive layer 130 is formed so as to cover the upper surface of the workpiece layer 110t.

[0079] As shown in Figure 5(d), the conductive layer 130 covering the upper surface of the workpiece layer 110t is removed by chemical mechanical polishing (CMP) or the like. This forms multiple wirings 130w in which the conductive layer 130 is filled into grooves TR of the workpiece layer 110.

[0080] With the above steps, the pattern formation process on the workpiece layer 110 and the processing of the wafer 100 in Embodiment 1 are completed.

[0081] The wiring 130w formed as described above becomes, for example, part of a semiconductor device. That is, the exposure method using the photomask 10 of Embodiment 1 shown in Figures 3 to 5, and the pattern formation process on the workpiece layer 110 are included in the manufacturing method of a semiconductor device.

[0082] (Overview) In high-NA-EUV exposure, to maintain the exposure area on the wafer that can be exposed with a photomask of, for example, 4x4x, the mask magnification becomes, for example, 4x8x. To maintain the size of the photomask used previously, exposure processing is sometimes performed by combining two photomasks of approximately the same size using stitching technology. In this case, in order to align the transfer patterns that span the two exposure areas, parts of these exposure areas may be overlapped. At this time, a problem arises in the double-exposure area that occurs at the junction of the exposure areas created by the two photomasks, such as an increase in the dimensional conversion difference of the transfer pattern.

[0083] Therefore, various methods have been proposed, such as not placing patterns that require precise control of dimensional conversion differences, such as fine patterns, in the stitching area (Stitching Band), adjusting the resolution of the stitching area so that appropriate resolution can be obtained by double exposure (At-Resolution Stitching), or creating a gradient in the amount of light in the stitching area by controlling the on / off state of the light source during exposure (Dose-Gradient Stitching).

[0084] However, the first method requires significant design changes, the second method is prone to process variations, and the third method makes it difficult to achieve precise positional accuracy for switching the light source on and off.

[0085] According to the photomask 10 of Embodiment 1, the reflection intensity of the exposure light decreases from the end E31 of the stitching region ST located inside the photomask 10 toward the other end E32 of the stitching region ST located at one end E12 of the photomask 10. This makes it possible to suppress the dimensional transformation difference that occurs in double exposure due to the overlapping of exposure regions EX1 and EX2.

[0086] According to the photomask 10 of Embodiment 1, the coverage of the light-shielding pattern P2 increases from the end E31 of the stitching region ST located inside the photomask 10 to the other end E32 of the stitching region ST located at one end E12 of the photomask 10. This reduces the reflection intensity of the exposure light and suppresses the dimensional transformation difference caused by double exposure due to the overlapping of exposure regions EX1 and EX2.

[0087] According to the photomask 10 of Embodiment 1, in the light-shielding pattern P22a, the number of dots per unit area increases from the end E31 of the stitching region ST located inside the photomask 10 to the other end E32 of the stitching region ST located at one end E12 of the photomask 10. This increases the coverage of the light-shielding pattern P22a toward the end E12 of the photomask 10, thereby reducing the reflection intensity of the exposed light.

[0088] According to the photomask 10 of Embodiment 1, in the light-shielding pattern P22b, the area of ​​individual dots increases from the edge E31 of the stitching region ST located inside the photomask 10 to the other edge E32 of the stitching region ST located at one end E12 of the photomask 10. This increases the coverage of the light-shielding pattern P22b toward the edge E12 of the photomask 10, thereby reducing the reflection intensity of the exposed light.

[0089] According to the photomask 10 of Embodiment 1, in the light-shielding pattern P22c, the number of dots per unit area and the area of ​​each dot increase from the end E31 of the stitching region ST located inside the photomask 10 to the other end E32 of the stitching region ST located at one end E12 of the photomask 10. This increases the coverage of the light-shielding pattern P22c toward the end E12 of the photomask 10, thereby reducing the reflection intensity of the exposed light.

[0090] According to the photomask 10 of Embodiment 1, in the light-shielding pattern P21a, the number of lines per unit area increases from the end E31 of the stitching region ST located inside the photomask 10 to the other end E32 of the stitching region ST located at one end E12 of the photomask 10. This increases the coverage of the light-shielding pattern P21a toward the end E12 of the photomask 10, thereby reducing the reflection intensity of the exposed light.

[0091] According to the photomask 10 of Embodiment 1, in the light-shielding pattern P21b, the width of individual lines increases from the end E31 of the stitching region ST located inside the photomask 10 to the other end E32 of the stitching region ST located at one end E12 of the photomask 10. This increases the coverage of the light-shielding pattern P21b toward the end E12 of the photomask 10, thereby reducing the reflection intensity of the exposed light.

[0092] According to the photomask 10 of Embodiment 1, in the light-shielding pattern P21c, the number of lines per unit area and the width of each line increase from the end E31 of the stitching region ST located inside the photomask 10 to the other end E32 of the stitching region ST located at one end E12 of the photomask 10. This increases the coverage of the light-shielding pattern P21c toward the end E12 of the photomask 10, thereby reducing the reflection intensity of the exposed light.

[0093] (Variation 1) In the above-described embodiment 1, the coverage rate of the light-shielding pattern P2 was changed in order to change the reflectance intensity in the stitching region ST of the photomask 10. However, the method for changing the reflectance intensity of the photomask is not limited to this.

[0094] Below, using Figure 6, we will explain an example of changing the reflectivity of a photomask by changing the thickness of the light-absorbing layer 15 of the light-shielding pattern P3.

[0095] Figure 6 is a schematic diagram showing an example of the configuration of light-shielding patterns P1 and P3 provided on the wafer-facing surface of a photomask according to Modification 1 of Embodiment 1. More specifically, Figure 6(a) is a plan view showing an example of the configuration of light-shielding patterns P1 and P3, and Figures 6(b) to 6(d) are cross-sectional views showing examples of the configuration of light-shielding patterns P1 and P3.

[0096] In Figure 6, the same reference numerals are used for components similar to those in Embodiment 1 described above, and their descriptions may be omitted.

[0097] As shown in Figures 6(a) to 6(d), the light-shielding pattern P3, like the light-shielding pattern P1, is a pattern composed of a light-absorbing layer 15 and a buffer layer 14 provided on the reflective layer 13, and is positioned between the light-shielding patterns P1 in the stitching region STa of the photomask of Modified Example 1.

[0098] Furthermore, while the light-absorbing layer 15 in light-shielding pattern P1 has a constant thickness, in light-shielding pattern P3, the light-absorbing layer 15 is configured to gradually increase in thickness from the edge E31 near the center of the photomask of the stitching region STa to the other edge E32 of the stitching region ST located at one end E12 of the photomask.

[0099] The light-absorbing layer 15 has a predetermined absorption rate for exposure light, and the amount of exposure light that reaches the reflective layer 13 without being absorbed by the light-absorbing layer 15 differs depending on the thickness of the light-absorbing layer 15. More specifically, the thinner the light-absorbing layer 15, the easier it is for the exposure light to reach the reflective layer 13 without being absorbed, and the thicker the light-absorbing layer 15, the more the exposure light is absorbed and the harder it is for it to reach the reflective layer 13. Therefore, by increasing the thickness of the light-absorbing layer 15 toward the edge E12 of the photomask, the amount of exposure light that reaches the reflective layer 13 decreases, and the reflectivity per unit area of ​​the photomask 10 can be reduced.

[0100] In the example shown in Figure 6(c), the light-shielding pattern P31, as the light-shielding pattern P3, has a gently sloping inclined surface 15t, so that it becomes thicker from one end E31 to the other end E32 of the stitching region STa. At this time, the thickness of the light-absorbing layer 15 can be made minimal or nearly zero at the end E31 of the stitching region STa near the center of the photomask, and the light-shielding pattern P31 can be configured such that the thickness of the light-absorbing layer 15 at a predetermined distance from the center of the photomask is equal to or greater than that of the light-absorbing layer 15 of the light-shielding pattern P1.

[0101] Such light-shielding patterns P1 and P31 can be formed, for example, as follows.

[0102] A buffer layer 14 and a light-absorbing layer 15 are formed in this order across the entire surface of the reflective layer 13. The portions of the light-absorbing layer 15 that will form the light-shielding patterns P1 and P31 are covered with a resist pattern, and the light-absorbing layer 15 and buffer layer 14 are sequentially etched under conditions that result in an anisotropic shape such as RIE. After the resist pattern is removed, a resist pattern is further formed that exposes the inclined surface 15t of the light-absorbing layer 15, and the light-absorbing layer 15 is further etched under conditions that result in a tapered shape. To create a tapered shape for the light-absorbing layer 15, techniques such as using conditions that facilitate the deposition of etching by-products, or using conditions with low selectivity from the resist pattern, can be employed to recede the resist pattern during etching.

[0103] As a result, a light-shielding pattern P1 having a light-absorbing layer 15 and a buffer layer 14 in a substantially vertical shape, and a light-shielding pattern P31 having a light-absorbing layer 15 with a tapered shape and an inclined surface 15t are formed.

[0104] In the example shown in Figure 6(d), the light-shielding pattern P32, as the light-shielding pattern P3, has a stepped section 15s instead of a gently sloping surface 15t, so that it gradually increases in thickness from one end E31 to the other end E32 of the stitching region STa. In this case as well, the thickness of the light-absorbing layer 15 can be made minimal or nearly zero at the end E31 of the stitching region STa near the center of the photomask, and the light-shielding pattern P32 can be configured such that the thickness of the light-absorbing layer 15 at a predetermined distance from the center of the photomask is equal to or greater than that of the light-absorbing layer 15 of the light-shielding pattern P1.

[0105] Such light-shielding patterns P1 and P32 can be formed, for example, as follows.

[0106] The process can be carried out in the same manner as described above for the light-shielding pattern P31 until the light-shielding pattern P1 is formed and the first resist pattern is formed. After the resist pattern is peeled off, a resist pattern is further formed in which a portion of the stepped portion 15s of the light-absorbing layer 15 is exposed, and the slimming of the resist pattern and etching of the light-absorbing layer 15 are repeated multiple times.

[0107] As a result, a light-shielding pattern P1 having a light-absorbing layer 15 and a buffer layer 14 in a substantially vertical shape, and a light-shielding pattern P31 having a light-absorbing layer 15 with a stepped portion 15s are formed.

[0108] In the photomask of Modified Example 1, in the light-shielding pattern P3, the light-absorbing layer 15 thickens from the end E31 of the stitching region STa located inside the photomask of Modified Example 1 to the other end E32 of the stitching region STa located at one end E12 of the photomask.

[0109] This increases the amount of exposure light absorbed by the light-shielding pattern P3 toward the edge E12 of the photomask in Modified Example 1, thereby reducing the reflectivity of the exposure light in the photomask of Modified Example 1. Therefore, it is possible to suppress the dimensional transformation difference caused by double exposure due to the superposition of exposure regions EX1 and EX2.

[0110] In the photomask of Modified Example 1, the light-shielding pattern P31 has a gently sloping inclined surface 15t of the light-absorbing layer 15 extending from the end E31 of the stitching region STa located inside the photomask of Modified Example 1 to the other end E32 of the stitching region STa located at one end E12 of the photomask. This increases the amount of exposure light absorbed by the light-shielding pattern P31 toward the end E12 of the photomask of Modified Example 1, and reduces the reflection intensity of exposure light in the photomask of Modified Example 1.

[0111] In the photomask of Modified Example 1, the light-absorbing layer 15 gradually thickens in the light-shielding pattern P32, from the edge E31 of the stitching region STa located inside the photomask of Modified Example 1 to the other edge E32 of the stitching region STa located at one end E12 of the photomask. This increases the amount of exposure light absorbed by the light-shielding pattern P32 toward the edge E12 of the photomask of Modified Example 1, thereby reducing the reflectivity of the exposure light in the photomask of Modified Example 1.

[0112] The photomask of the modified example 1 also produces the same effects as the embodiment 1 described above.

[0113] (Modification 2) Next, as yet another method for changing the reflection intensity of the photomask, we will describe the modified photomask 10b in Figure 7.

[0114] Figure 7 is a schematic diagram showing an example of the configuration of a photomask 10b according to a modification 2 of Embodiment 1. More specifically, Figure 7(a) is a cross-sectional view of the photomask 10b with the pellicle 20 attached, and Figures 7(b) and 7(c) are enlarged cross-sectional views showing several examples of the reflective layer 13b provided by the photomask 10b.

[0115] In Figure 7, the same reference numerals are used for components similar to those in Embodiment 1 described above, and their descriptions may be omitted.

[0116] As shown in Figure 7(a), the photomask 10b has a reflective layer 13b (131b, 132b) that becomes thinner toward the edge E12 of the photomask 10b, instead of the reflective layer 13 of Embodiment 1 described above. For example, the photomask 10b has a light-shielding pattern P1 similar to Embodiment 1, and the reflective layer 13b exposed from the light-shielding pattern P1 becomes thinner toward the edge E12 of the photomask 10b.

[0117] In the reflective layer 13b, the reflectivity of exposure light such as EUV differs depending on its thickness. More specifically, the reflective layer 13b, like the reflective layer 13 in Embodiment 1 described above, has a multilayer structure in which, for example, multiple Mo layers and multiple Si layers are alternately stacked one layer at a time, and the exposure light is diffracted by each of these layers and reflected out of the reflective layer 13b. Therefore, the thinner the reflective layer 13b and the fewer layers there are, the lower the reflectivity of the exposure light, and the thicker the reflective layer 13b and the more layers there are, the higher the reflectivity of the exposure light.

[0118] Therefore, by reducing the thickness of the reflective layer 13b toward the edge E12 of the photomask 10b, the reflectivity of the exposure light decreases, and the reflectivity per unit area of ​​the photomask 10b can be reduced.

[0119] In the example shown in Figure 7(b), the reflective layer 131b, which is the reflective layer 13b, has a gently sloping inclined surface 13t, so that it gradually thins out from one end E31 to the other end E32 of the stitching region STb. At this time, the thickness of the reflective layer 131b can be set to the maximum at the end E31 near the center of the photomask 10b, i.e., to a thickness that provides sufficient reflectivity for exposure of the photoresist layer, etc., and the thickness of the reflective layer 131b can be set to the minimum or nearly zero at the end E12 of the photomask 10b.

[0120] Such a reflective layer 131b can be formed, for example, as follows.

[0121] A reflective layer 13 similar to that in Embodiment 1 is formed on the entire surface of the glass substrate 12, and a resist pattern is formed in which the portion that will become the inclined surface 13t of the reflective layer 131b is exposed, and the reflective layer 13 is etched under conditions that result in a tapered shape. In order to make the reflective layer 13b tapered, for example, methods such as using conditions that make it easy for etching by-products to accumulate, or using conditions with low selectivity from the resist pattern, can be employed to recede the resist pattern during etching.

[0122] As a result, a reflective layer 131b with a tapered shape and an inclined surface 13t is formed.

[0123] In the example shown in Figure 7(c), the reflective layer 132b, which serves as the reflective layer 13b, has a stepped section 13s instead of a gently sloping surface 13t, so that the stitching region STb gradually thins from one end E31 to the other end E32. This shape of the reflective layer 132b can be obtained, for example, by processing multiple layers of Mo and Si in a stepped manner.

[0124] In this case, the number of layers of the reflective layer 132b can be set to the maximum at the edge E31 near the center of the photomask 10b in the stitching region STb, that is, to a number of layers that provides sufficient reflectivity for exposure of the photoresist layer, etc., while the number of layers of the reflective layer 132b can be set to the minimum or nearly zero at the edge E12 position of the photomask 10b.

[0125] Such a reflective layer 132b can be formed, for example, as follows.

[0126] A reflective layer 13 of Embodiment 1 is formed on the entire surface of the glass substrate 12, and a resist pattern is formed in which a portion of the stepped portion 13s of the reflective layer 132b is exposed. The slimming of the resist pattern and etching of multiple layers each of the Mo layer and Si layer of the reflective layer 13 are repeated multiple times.

[0127] As a result, a reflective layer 132b having a stepped portion 13s is formed.

[0128] Furthermore, when the Mo layer and Si layer of the reflective layer 132 are formed by sputtering or the like, it is also possible to form the reflective layer 132 so that it has a stepped portion 13s during the film deposition stage.

[0129] In this case, a shielding plate or the like is placed between the glass substrate 12 on which the reflective layer 132 is formed and the sputtering target, and the position of the shielding plate is gradually shifted to narrow the area in which sputtered particles adhere and the Mo layer and Si layer are formed. A reflective layer 132b having a stepped portion 13s can also be formed by this method.

[0130] According to the photomask 10b of the modified example 2, the reflective layer 13b thins from the edge E31 of the stitching region STb located inside the photomask 10b to the other edge E32 of the stitching region STb located at one end E12 of the photomask 10b.

[0131] This reduces the reflectivity of the exposure light by the reflective layer 13b toward the edge E12 of the photomask 10b, thereby decreasing the reflection intensity of the exposure light. Thus, it is possible to suppress the dimensional transformation difference caused by double exposure due to the superposition of exposure regions EX1 and EX2.

[0132] According to the photomask 10b of the modified example 2, the reflective layer 131b has an inclined surface 13t that slopes gently from the end E31 of the stitching region STb located inside the photomask 10b to the other end E32 of the stitching region STb located at one end E12 of the photomask 10b. This reduces the reflectivity of the exposure light by the reflective layer 131b toward the end E12 of the photomask 10b, thereby reducing the reflection intensity of the exposure light.

[0133] In the photomask 10b of the modified example 2, the reflective layer 132b gradually thins out as the stretching distance between the multiple Mo layers and Si layers decreases, from the edge E31 of the stitching region STb located inside the photomask 10b to the other edge E32 of the stitching region STb located at one end E12 of the photomask 10b. This reduces the reflectivity of the exposure light by the reflective layer 132b toward the edge E12 of the photomask 10b, thereby reducing the reflection intensity of the exposure light.

[0134] The photomask 10b of the modified example 2 also provides the same effects as the embodiment 1 described above.

[0135] [Embodiment 2] In the above-described embodiment 1, the reflection intensity of the photomasks 10, 10b themselves is changed by the configuration of each part of the photomasks 10, 10b, etc., and the amount of light in the double-exposure exposure region Dex is adjusted. However, the method for adjusting the amount of light in the double-exposure region is not limited to this.

[0136] The configuration of Embodiment 2, which adjusts the light intensity of the double exposure area using a method different from Embodiment 1, will be described in detail below with reference to the drawings. In the following drawings, components similar to those in Embodiment 1 described above are denoted by the same reference numerals, and their descriptions may be omitted.

[0137] (Example of pellicle configuration) Figure 8 is a schematic diagram showing an example configuration of the photomask 10c according to Embodiment 2. More specifically, Figure 8(a) is a cross-sectional view of the photomask 10c with the pellicle 20 attached, and Figure 8(b) is an enlarged cross-sectional view of the pellicle 200.

[0138] As shown in Figure 8(a), the photomask 10c comprises a conductive layer 11, a glass substrate 12, a reflective layer 13, and a light-shielding pattern P1 including a buffer layer 14 and a light-absorbing layer 15. A stitching region STc is also provided near one end E12 of the photomask 10c.

[0139] The pellicle 200 comprises a protective layer 210 and a frame 22.

[0140] The protective layer 210 is, for example, a carbon nanotube layer, and its thickness changes in the region PL, which corresponds to the stitching region STc and through which exposure light reflected from the stitching region STc is transmitted. More specifically, the protective layer 210 becomes thicker from one end E21 to the other end E22 of the region PL, which corresponds to the stitching region STc.

[0141] Here, the end E21 in the above region PL is located at a position corresponding to the end E31 of the stitching region STc that is closer to the center of the photomask 10c, and the end E22 in the above region PL is located at a position corresponding to the other end E32 of the stitching region ST, which is located at the end E12 of the photomask 10c.

[0142] As shown in Figure 8(b), the protective layer 210, whose thickness changes as described above, has a stepped section 210s.

[0143] As described above, the protective layer 210 has high transmittance to exposure light such as EUV, but the transmittance of exposure light can be reduced by increasing the thickness of the protective layer 210. Therefore, by increasing the thickness of the protective layer 210 toward the position corresponding to the edge E12 of the photomask 10c, the amount of exposure light that passes through the protective layer 210 and reaches the reflective layer 13 is reduced, and the reflectance per unit area of ​​the photomask 10c can be reduced.

[0144] Furthermore, the pellicle 200 of Embodiment 2 may also further include an oxidation-inhibiting layer that covers the protective layer 210 and suppresses oxidation of the protective layer 210.

[0145] (Method of manufacturing pellicle) Next, the manufacturing method of the pellicle 200 according to Embodiment 2 will be described using Figures 9 and 10. Figures 9 and 10 are cross-sectional views illustrating, in order, a part of the manufacturing method of the pellicle 200 according to Embodiment 2.

[0146] As shown in Figure 9(a), a thin layer 210b, such as a carbon nanotube layer, is formed on the support substrate 320 by CVD or the like.

[0147] As shown in Figure 9(b), the support substrate 320 on which the thin layer 210b is formed is immersed in pure water or the like in the immersion tank BT to peel off the thin layer 210b from the support substrate 320.

[0148] As shown in Figure 9(c), a thin layer 210a, such as a carbon nanotube layer, is formed on a support substrate 310, which is different from the support substrate 320, by CVD or the like, so that its stretching distance is longer than that of the thin layer 210b, and the peeled thin layer 210b is then superimposed on the thin layer 210a.

[0149] As shown in Figure 9(d), a thin layer 210c with a shorter stretching distance than the thin layer 210b is formed on the support substrate 320 by CVD or the like, and then peeled off by immersion in the immersion tank BT.

[0150] As shown in Figure 9(e), the thin layer 210c is superimposed and attached onto the thin layer 210b of the support substrate 310.

[0151] As shown in Figures 10(a) to 10(f), the above process is repeated to sequentially layer and attach thin layers 210d to 210h, such as a carbon nanotube layer, onto the thin layer 210c of the support substrate 310. This forms a protective layer 210 in which multiple thin layers 210a to 210h are stacked.

[0152] After that, the protective layer 210 is attached to the frame 22.

[0153] The pellicle 200 of Embodiment 2 is manufactured as described above.

[0154] (Overview) According to the photomask 10c of Embodiment 2, the protective layer 210 of the pellicle 200 thickens in the region PL of the pellicle 200 from the end E21 corresponding to the inner position of the photomask 10c to the other end E22 corresponding to one end E12 of the photomask 10c.

[0155] This reduces the amount of exposure light reaching the reflective layer 13 towards the edge E12 of the photomask 10c, thereby decreasing the reflection intensity of the exposure light. Therefore, it is possible to suppress the dimensional transformation difference caused by double exposure due to the superposition of exposure regions EX1 and EX2.

[0156] The photomask 10c of Embodiment 2 also provides the same effects as those of Embodiment 1 described above.

[0157] In the above-described embodiment 2, the protective layer 210 was, for example, a carbon nanotube layer. However, the protective layer 210 in embodiment 2 may be, as described in embodiment 1, a graphene layer, a polyimide layer, a polysilicon layer, or a silicon carbide layer, for example. Even with a protective layer 210 made of these materials, the above effect can be obtained by changing the transmittance of exposure light, etc., by changing the thickness.

[0158] (Variation 1) In the above-described embodiment 2, the protective layer 210 was formed by stacking thin layers 210a to 201h, such as carbon nanotube layers, one layer at a time. However, the method for forming the protective layer 210 with varying thickness is not limited to the above.

[0159] In the following Modification 1, an example of a method for forming the protective layer 210 using a different method than that of Embodiment 2 will be described using Figures 11 to 15. Modification 1 differs from Embodiment 2 in that the protective layer 210 is formed by immersion.

[0160] Figures 11 to 15 are cross-sectional views illustrating, in order, a part of the manufacturing method of the pellicle 200 according to Modification 1 of Embodiment 2. In Figures 11 to 15, components similar to those in Embodiment 2 described above are denoted by the same reference numerals, and their descriptions may be omitted.

[0161] As shown in Figure 11(a), a thin layer 210a, such as a carbon nanotube layer, is formed on the support substrate 310 by CVD or the like. However, the thin layer 210a may also be formed by immersion or the like, as detailed below.

[0162] As shown in Figure 11(b), a portion of the support substrate 310 on which the thin layer 210a is formed is immersed in the carbon nanotube dispersion DSP in the immersion tank BT. The carbon nanotube dispersion DSP is a liquid in which fine molecules of carbon nanotubes are dispersed in pure water or an organic solvent, and commercially available products can be used.

[0163] As shown in Figure 12, when the support substrate 310, which has been immersed in a carbon nanotube dispersion DSP, is withdrawn from the dispersion DSP, a new thin layer 210b, such as a carbon nanotube layer, is formed on the support substrate 310, covering a portion of the thin layer 210a.

[0164] At this time, a thin layer 210b may also be formed on the back side of the support substrate 310. From this point onward, the illustration and explanation of the thin layer formed on the back side of the support substrate 310 by repeating the same process will be omitted.

[0165] As shown in Figure 13(a), a portion of the support substrate 310, on which thin layers 210a and 210b are formed, is immersed in the dispersion liquid DSP. At this time, the support substrate 310 is immersed more shallowly than in the process shown in Figure 11(b).

[0166] As shown in Figure 13(b), by withdrawing the support substrate 310 from the dispersion DSP, a new thin layer 210c is formed that covers a portion of the thin layer 210b.

[0167] As shown in Figure 13(c), a portion of the support substrate 310, on which thin layers 210a to 210c are formed, is immersed in the dispersion liquid DSP. At this time, the support substrate 310 is immersed even more shallowly than in the process shown in Figure 12(a).

[0168] As shown in Figure 14(a), by withdrawing the support substrate 310 from the dispersion DSP, a new thin layer 210d is formed that covers a portion of the thin layer 210c.

[0169] As shown in Figure 14(b), a portion of the support substrate 310 on which the thin layers 210a to 210d are formed is immersed in the dispersion liquid DSP and then pulled out. This forms a new thin layer 210e that covers a portion of the thin layer 210d.

[0170] As shown in Figure 15, by repeating the above immersion treatment, a protective layer 210 is obtained in which thin layers 210a to 2120h with gradually shorter stretching distances are laminated.

[0171] After that, the protective layer 210 is attached to the frame 22.

[0172] The pellicle 200 of Embodiment 2 is manufactured as described above.

[0173] According to the manufacturing method of the pellicle 200 of the modified example 1, a pellicle 200 that has the same effects as the embodiment 2 described above can be obtained.

[0174] (Modification 2) In the following Modification 2, an example of a method for forming the protective layer 210 using a different method from Embodiment 2 and Modification 1 will be described with reference to Figure 16. Modification 2 differs from Embodiment 2 and others described above in that the protective layer 210 is formed by compression.

[0175] Figure 16 is a cross-sectional view illustrating a part of the manufacturing method of the pellicle 200 according to a modified example 2 of Embodiment 2. In Figure 16, components similar to those in Embodiment 2 described above are denoted by the same reference numerals, and their descriptions may be omitted.

[0176] As shown in Figure 16(a), a thick film layer 210t, such as a carbon nanotube layer, is formed on the support substrate 310. Such a layer 210t preferably has a low layer density and can be formed, for example, by spraying the carbon nanotube dispersion DSP onto the support substrate 310 using a sprayer (not shown). The layer 210t may also be formed by the immersion treatment described above.

[0177] Furthermore, a mold 400 having a stepped shape is placed opposite the layer 210t on the support substrate 310. The mold 400 can be made of any material arbitrarily selected from various materials such as metal, ceramic, or resin.

[0178] As shown in Figure 16(b), the mold 400 is pressed against the layer 210t on the support substrate 310 to compress and mold the layer 210t. As described above, since the layer 210t is formed at a low density, it can be compressed by the mold 400 and molded into the desired shape. It is preferable to adjust the layer density when forming the layer 210t so that the desired layer density is achieved after compression.

[0179] As shown in Figure 16(c), the protective layer 210 is obtained by demolding the mold 400.

[0180] After that, the protective layer 210 is attached to the frame 22.

[0181] The pellicle 200 of Embodiment 2 is manufactured as described above.

[0182] According to the manufacturing method of the pellicle 200 of the modified example 2, a pellicle 200 that has the same effects as the embodiment 2 described above can be obtained.

[0183] (Variation 3) In the following Modification 3, an example of a method for forming the protective layer 210 using a method further different from that of Embodiment 2 and Modifications 1 and 2 will be described using Figures 17 to 19. Modification 3 differs from Embodiment 2 and others described above in that the protective layer 210 is formed by spraying.

[0184] Figures 17 to 19 are cross-sectional views illustrating, in order, a part of the manufacturing method of the pellicle 200 according to a modified example 3 of Embodiment 2. In Figures 17 to 19, components similar to those in Embodiment 2 described above are denoted by the same reference numerals, and their descriptions may be omitted.

[0185] As shown in Figure 17(a), a dispersion liquid DSP such as carbon nanotubes is sprayed by the sprayer 510 to form a thin layer 210a such as a carbon nanotube layer on the support substrate 310. A shielding plate 520 is placed above the support substrate 310 on which the thin layer 210a is formed to shield a portion of the support substrate 310 from the spraying of the dispersion liquid DSP by the sprayer 510.

[0186] The shielding plate 520 can be made of any material that does not dissolve or deteriorate in the dispersion liquid DSP, such as metal, ceramic, or resin, which can be arbitrarily selected from a variety of materials.

[0187] As shown in Figure 17(b), after forming a thin layer 210b that covers a portion of the thin layer 210a by partially shielding the support substrate 310, the shielding plate 520 is slid to expand the shielded area, and the dispersion liquid DSP is sprayed.

[0188] As shown in Figure 17(c), after expanding the shielding area of ​​the support substrate 310 to form a thin layer 210c that covers a portion of the thin layer 210b, the shielding plate 520 is further slid to further expand the shielding area, and then the dispersion liquid DSP is sprayed.

[0189] As shown in Figures 18(a) to 18(c), the shielding area is expanded by the shielding plate 520 and the dispersion liquid DSP is sprayed by the sprayer 510, and these processes are repeated multiple times to sequentially form thin layers 210d to 210f on the support substrate 310.

[0190] As shown in Figures 19(a) and 19(b), the shielding area is expanded by the shielding plate 520 and the dispersion liquid DSP is sprayed by the sprayer 510, and these processes are repeated to sequentially form thin layers 210g and 210h on the support substrate 310. This forms a protective layer 210 on the support substrate 310.

[0191] After that, the protective layer 210 is attached to the frame 22.

[0192] The pellicle 200 of Embodiment 2 is manufactured as described above.

[0193] According to the manufacturing method of the pellicle 200 of the modified example 3, a pellicle 200 that has the same effects as the embodiment 2 described above can be obtained.

[0194] (Modification 4) In the above-described embodiment 2 and modifications 1 to 3, the intensity of reflected light from the photomask 10c is changed by changing the thickness of the protective layer 210 of the pellicle 200, thereby adjusting the amount of light in the double-exposure exposure region Dex. However, the method of adjusting the amount of light in the double-exposure region using the pellicle is not limited to this.

[0195] In the following Modification 4, Figure 20 will be used to describe a method for adjusting the light intensity using the pellicle 200a in a manner different from that of Embodiment 2 and Modifications 1 to 3.

[0196] Figure 20 is a schematic diagram showing an example of the configuration of a photomask 10c according to a modification 4 of Embodiment 2. More specifically, Figure 20(a) is a cross-sectional view of the photomask 10c with the pellicle 200a attached, and Figure 20(b) is an enlarged cross-sectional view of the pellicle 200a.

[0197] As shown in Figure 20(a), the pellicle 200a comprises a protective layer 21, an oxidation-inhibiting layer 23, and a frame 22.

[0198] The oxidation suppression layer 23 is, for example, an SiO2 layer or a SiN layer, and is arranged to cover the wafer-facing surface of the protective layer 21 in order to suppress oxidation of the protective layer 21. Furthermore, in the modified example 4, the oxidation suppression layer 23 has varying thickness in the region corresponding to the stitching region STc. More specifically, in the region PL of the pellicle 200a, the oxidation suppression layer 23 thickens from the edge E21 corresponding to the edge E31 near the center of the photomask 10c of the stitching region STc, to the edge E22 corresponding to the other edge E32 of the stitching region STc located at the edge E12 of the photomask 10c.

[0199] As shown in Figure 20(b), the oxidation-suppressing layer 23, whose thickness changes as described above, has a stepped section 23s.

[0200] The oxidation-suppressing layer 23, like the protective layer 21, has high transmittance to exposure light such as EUV, but the transmittance of exposure light can be reduced by increasing the thickness of the oxidation-suppressing layer 23. Therefore, by increasing the thickness of the oxidation-suppressing layer 23 toward the position corresponding to the edge E12 of the photomask 10c, the amount of exposure light reaching the reflective layer 13 is reduced, and the reflectance intensity per unit area of ​​the photomask 10c can be reduced.

[0201] The oxidation-suppressing layer 23 having such a shape can also be formed by CVD or the like, and by etching or the like.

[0202] According to the photomask 10c of the modified example 4, the oxidation-suppressing layer 23 of the pellicle 200a thickens in the region PL of the pellicle 200a from the end E21 corresponding to the inner position of the photomask 10c to the other end E22 corresponding to one end E12 of the photomask 10c.

[0203] This reduces the amount of exposure light reaching the reflective layer 13 towards the edge E12 of the photomask 10c, thereby decreasing the reflection intensity of the exposure light. Thus, it is possible to suppress the dimensional transformation difference caused by double exposure due to the superposition of exposure regions EX1 and EX2.

[0204] The photomask 10c of the modified example 4 also provides the same effects as the embodiment 2 described above.

[0205] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0206] 10, 10b, 10c... Photomask, 12... Glass substrate, 13, 13b, 131b, 132b... Reflective layer, 14... Buffer layer, 15... Light absorption layer, 13s, 15s, 23s, 210s... Staircase section, 13t, 15t... Inclined surface, 20, 200, 200a... Pellicle, 21, 210... Protective layer, 22... Frame, 23... Oxidation suppression layer, 100... Wafer, EX1, EX2, Dex... Exposure area, P1, P2, P3, P21a~P21c, P22a~P22c, P31, P32... Light shielding pattern, SH... Shot area, ST, STa~STc... Stitching area.

Claims

1. A photomask including a stitching region having a first end at one end and a second end at a predetermined distance inward from the first end, circuit board and A reflective layer is disposed on the first surface of the substrate and reflects light, The reflective layer comprises a light-shielding pattern including a light-absorbing layer that absorbs light, which is disposed on a second surface opposite to the substrate of the reflective layer, In the stitching region, The reflection intensity of the light is configured to be lower at the first end than at the second end. Photomask.

2. The aforementioned light-shielding pattern is A first light-shielding pattern is disposed on the second surface of the reflective layer including the stitching region, The reflective layer includes a second light-shielding pattern disposed in the stitching region of the second surface of the reflective layer, The coverage ratio of the second light-shielding pattern is The first end of the stitching region is larger than the second end. The photomask according to claim 1.

3. The coverage ratio of the second light-shielding pattern is The stitching region increases in stages from the second end toward the first end. The photomask according to claim 2.

4. The first light-shielding pattern is, Displaced in the region between the one end and the other end relative to the one end, The photomask according to claim 2.

5. The aforementioned light-shielding pattern is A first light-shielding pattern is disposed on the second surface of the reflective layer including the stitching region, The reflective layer includes a second light-shielding pattern disposed in the stitching region of the second surface of the reflective layer, In the second light-shielding pattern described above, The light-absorbing layer is thicker on the first end side than on the second end side of the stitching region. The photomask according to claim 1.

6. The aforementioned reflective layer is The first end of the stitching region is thinner than the second end. The photomask according to claim 1.

7. circuit board and A reflective layer is disposed on the first surface of the substrate and reflects light, A light-shielding pattern is provided on the second surface of the reflective layer opposite to the substrate, and includes a light-absorbing layer that absorbs the light. A pellicle is provided which is positioned at a predetermined distance from the light-shielding pattern and faces the first surface, The aforementioned pellicle is The region includes a first end located at a position corresponding to one end of the substrate, and a second end located at a position corresponding to a position located a predetermined distance inward from the first end of the substrate. Having a first layer that becomes thicker from the second end toward the first end, Photomask.

8. The first layer is, This is a protective layer that protects the light-shielding pattern. The photomask according to claim 7.

9. The aforementioned pellicle is The first layer further comprises a second layer covering a third surface facing the light-shielding pattern of the first layer, The first layer is an oxidation-inhibiting layer that suppresses oxidation of the second layer, The second layer is a protective layer that protects the light-shielding pattern. The photomask according to claim 7.

10. A first region extending from one end of a shot region on a wafer to a position a first distance inside the shot region is exposed using a first photomask. By exposing a second region, which is located a second distance inside the shot region from the other end of the shot region and extends to a position within the first region, using a second photomask, the entire shot region is exposed while the third region located in the center of the shot region is double-exposed. The first and second photomasks are, The stitching region corresponds to the third region and has a first end at one end of each of the first and second photomasks, and a second end at a predetermined distance inward from the first end, circuit board and A reflective layer is disposed on the first surface of the substrate and reflects light, The reflective layer comprises a light-shielding pattern including a light-absorbing layer that absorbs light, which is disposed on a second surface opposite to the substrate of the reflective layer, In the stitching region, The reflection intensity of the light is configured to be lower at the first end than at the second end. Exposure method.

11. A first region extending from one end of a shot region on a wafer to a position a first distance inside the shot region is exposed using a first photomask. By exposing a second region, which is located a second distance inside the shot region from the other end of the shot region and extends to a position within the first region, using a second photomask, the entire shot region is exposed while the third region located in the center of the shot region is double-exposed. The first and second photomasks are, circuit board and A reflective layer is disposed on the first surface of the substrate and reflects light, A light-shielding pattern is provided on the second surface of the reflective layer opposite to the substrate, and includes a light-absorbing layer that absorbs the light. The pellicle is positioned at a predetermined distance from the light-shielding pattern and faces the first surface, The aforementioned pellicle is A region corresponding to the third region, having a first end at a position corresponding to one end of each of the first and second photomasks, and a second end at a position corresponding to a position located a predetermined distance inward from one end of each of the first and second photomasks, Having a first layer that becomes thicker from the second end toward the first end, Exposure method.

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