A multilayer film material, an extreme ultraviolet light mirror and a preparation method and application thereof

Abstract

This invention belongs to the field of extreme ultraviolet (EUV) optical element technology, specifically relating to a multilayer film material, an EUV mirror, its fabrication method, and its applications. The invention provides a multilayer film material comprising stacked periodic units, each periodic unit consisting of sequentially stacked B4C, Mo, Y, and Si layers; the two side layers of the multilayer film material are B4C and Si layers, respectively. By adding a Y layer between the Mo and Si layers and a B4C layer between the Si and Mo layers, this invention suppresses diffusion between the Mo and Si layers, thereby improving the boundary clarity between the Mo and Si layers in the multilayer film material, and consequently increasing the reflectivity of the multilayer film material to EUV light.

Description

Technical Field

[0001] This invention belongs to the field of extreme ultraviolet (EUV) optical element technology, specifically relating to a multilayer film material, an EUV reflector, its preparation method, and its application. Background Technology

[0002] The extreme ultraviolet (EUV) band typically refers to the wavelength range of 121 nm to 10 nm (corresponding to photon energies from 10.25 electron volts to 124 electron volts, respectively). With the miniaturization and high performance of integrated circuits, photolithography has become one of the manufacturing processes for integrated circuits. EUV lithography, as a possible method for manufacturing very large-scale integrated circuits, has attracted considerable attention. An EUV lithography machine mainly consists of an EUV light source system, an EUV light reflection system, and an illumination, exposure, and etching system. The EUV light reflection system mainly consists of EUV mirrors, which are currently primarily constructed from Mo / Si multilayer films. At an EUV wavelength of 13.5 nm, Mo and Si exhibit high optical contrast and low absorption rates of EUV light, which is beneficial for reflecting EUV light. The theoretical peak reflectivity of Mo / Si multilayer film mirrors is 74.06%.

[0003] Research has shown that in extreme ultraviolet (EUV) reflective systems, using 10 mirrors consecutively to project patterns onto wafers results in a maximum reflectivity of only about 3% in the final stage. A 1% increase in the reflectivity of multilayer mirrors can increase the overall yield of the EUV lithography system by approximately 15%. To further improve the utilization rate of EUV light in EUV lithography machines, it is necessary to further enhance the reflectivity of the EUV reflective film. Summary of the Invention

[0004] In view of this, the present invention provides a multilayer film material, an extreme ultraviolet (EUV) light reflector, a preparation method thereof, and an application thereof. The multilayer film material provided by the present invention has a high reflectivity for EUV light, and its use in EUV light reflectors of EUV lithography machines can improve the utilization rate of EUV light by EUV lithography machines.

[0005] To address the aforementioned technical problems, the present invention provides a multilayer film material comprising stacked periodic units, wherein the periodic units include sequentially stacked B4C layers, Mo layers, Y layers, and Si layers; the two sides of the multilayer film material are B4C layers and Si layers, respectively.

[0006] Preferably, in one periodic unit, the thickness of the B4C layer is 0.48–0.52 nm, the thickness of the Mo layer is 2.22–2.26 nm, the thickness of the Y layer is 0.48–0.52 nm, and the thickness of the Si layer is 3.67–3.71 nm.

[0007] Preferably, the thickness of a periodic unit is 6.9–6.98 nm.

[0008] Preferably, the number of periodic units is 40 to 60.

[0009] The present invention also provides an extreme ultraviolet light reflector, comprising a substrate and a multilayer film on the substrate surface, wherein the multilayer film is composed of the multilayer film material described in the above technical solution; the substrate surface is in direct contact with the B4C layer in the multilayer film.

[0010] Preferably, the substrate comprises a monocrystalline silicon wafer, quartz, or K9 glass;

[0011] The roughness of the substrate is 0.28–0.32 nm.

[0012] The present invention also provides a method for preparing the extreme ultraviolet light reflector described in the above technical solution, comprising the following steps:

[0013] A B4C layer, a Mo layer, a Y layer and a Si layer are sequentially deposited on the substrate surface to form a periodic unit, and the periodic unit is repeatedly deposited to form a multilayer film.

[0014] Preferably, the deposition method includes magnetron sputtering or pulsed laser deposition.

[0015] Preferably, when the deposition method is magnetron sputtering, the sputtering power for depositing the B4C layer is 110-130W, the sputtering power for depositing the Mo layer is 40-60W, the sputtering power for depositing the Y layer is 10-20W, and the sputtering power for depositing the Si layer is 90-110W.

[0016] The present invention also provides the application of the extreme ultraviolet light reflector described in the above technical solution or the extreme ultraviolet light reflector prepared by the preparation method described in the above technical solution in an extreme ultraviolet lithography machine.

[0017] This invention provides a multilayer film material comprising stacked periodic units, wherein each periodic unit includes a B4C layer, a Mo layer, a Y layer, and a Si layer stacked sequentially; the two side layers of the multilayer film material are a B4C layer and a Si layer, respectively. This invention adds a Y layer between the Mo and Si layers and a B4C layer between the Si and Mo layers, which can suppress diffusion between the Mo and Si layers, thereby improving the boundary clarity of the Mo and Si layers in the multilayer film material, and thus improving the reflectivity of the multilayer film material to extreme ultraviolet light. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of an extreme ultraviolet light reflector, where 1 is the substrate, 2 is the B4C layer, 3 is the Mo layer, 4 is the Y layer, 5 is the Si layer, 6 is the periodic unit, and 7 is the multilayer film material.

[0019] Figure 2 The reflectance curves are shown for the extreme ultraviolet reflectors prepared in Example 1 and Comparative Examples 1-3. Detailed Implementation

[0020] The present invention provides a multilayer film material comprising stacked periodic units, wherein the periodic units include sequentially stacked B4C layers, Mo layers, Y layers and Si layers; the two sides of the multilayer film material are B4C layers and Si layers, respectively.

[0021] In this invention, the thickness of the B4C layer in one periodic unit is preferably 0.48–0.52 nm, more preferably 0.5 nm; the thickness of the Mo layer in one periodic unit is preferably 2.22–2.26 nm, more preferably 2.24 nm; the thickness of the Y layer in one periodic unit is preferably 0.48–0.52 nm, more preferably 0.5 nm; and the thickness of the Si layer in one periodic unit is preferably 3.67–3.71 nm, more preferably 3.69 nm. In this invention, the thickness of one periodic unit is preferably 6.9–6.98 nm, more preferably 6.93 nm. In this invention, the operating wavelength and the thickness of one periodic unit preferably satisfy the Bragg equation. In this invention, when the thickness of one periodic unit is 6.93 nm, the multilayer film material exhibits good reflectivity for extreme ultraviolet light with a wavelength of 13.5 nm.

[0022] In this invention, the number of periodic units is preferably 40 to 60, more preferably 50 to 55.

[0023] In this invention, the B4C layer has good thermal stability, which can improve the thermal stability of the multilayer film material.

[0024] The multilayer film material is preferably prepared by magnetron sputtering in this invention. In this invention, the magnetron sputtering is preferably DC magnetron sputtering. In this invention, the purity of the B4C target used for magnetron sputtering the B4C layer is preferably 99-99.8%, more preferably 99.5%; the purity of the Mo target used for magnetron sputtering the Mo layer is preferably 99.9-99.99%, more preferably 99.99%; the purity of the Y target used for magnetron sputtering the Y layer is preferably 99.9-99.99%, more preferably 99.99%; and the purity of the Si target used for magnetron sputtering the Si layer is preferably 99.9-99.999%, more preferably 99.999%. In this invention, the sputtering power of the magnetron sputtered B4C layer is preferably 110-130W, more preferably 115-120W; the sputtering power of the magnetron sputtered Mo layer is preferably 40-60W, more preferably 50-55W; the sputtering power of the magnetron sputtered Y layer is preferably 10-20W, more preferably 15-18W; and the sputtering power of the magnetron sputtered Si layer is preferably 90-110W, more preferably 95-100W. In this invention, the sputtering rate of the magnetron sputtering B4C layer is preferably 0.06–0.15 nm / s, more preferably 0.08 nm / s; the sputtering rate of the magnetron sputtering deposited Mo layer is preferably 0.12–0.43 nm / s, more preferably 0.28 nm / s; the sputtering rate of the magnetron sputtering deposited Y layer is preferably 0.08–0.19 nm / s, more preferably 0.14 nm / s; and the sputtering rate of the magnetron sputtering deposited Si layer is preferably 0.16–0.63 nm / s, more preferably 0.42 nm / s. In this invention, the working gas for magnetron sputtering is preferably argon, and the purity of the argon is preferably 99.999%; the pressure of the working gas is preferably 0.14–0.16 Pa, more preferably 0.15 Pa. In this invention, the base vacuum of the magnetron sputtering is preferably 1.8 × 10⁻⁶. -4 ~2.2×10 -4 Pa, more preferably 2×10 Pa -4 Pa.

[0025] This invention utilizes magnetron sputtering to prepare multilayer film materials, which can precisely control the thickness of each layer and improve the uniformity of each layer, thereby increasing the reflectivity of the multilayer film material to extreme ultraviolet light.

[0026] This invention also provides an extreme ultraviolet (EUV) reflector, comprising a substrate and a multilayer film on the substrate surface, wherein the multilayer film is composed of the multilayer film material described in the above-described technical solution; the substrate surface is in direct contact with the B4C layer in the multilayer film. In this invention, the substrate preferably comprises a monocrystalline silicon wafer, quartz, or K9 glass, more preferably a monocrystalline silicon wafer. In this invention, the monocrystalline silicon wafer is preferably oriented 100°. In this invention, the roughness of the substrate is preferably 0.28–0.32 nm, more preferably 0.3 nm. Limiting the substrate roughness to the above range in this invention can further improve the reflectivity of the EUV reflector.

[0027] In this invention, Figure 1 The diagram shows the structure of the extreme ultraviolet reflector, where 1 is the substrate, 2 is the B4C layer, 3 is the Mo layer, 4 is the Y layer, 5 is the Si layer, 6 is the periodic unit, and 7 is the multilayer film.

[0028] The present invention also provides a method for preparing the extreme ultraviolet light reflector described in the above technical solution, comprising the following steps:

[0029] A B4C layer, a Mo layer, a Y layer and a Si layer are sequentially deposited on the substrate surface to form a periodic unit, and the periodic unit is repeatedly deposited to form a multilayer film.

[0030] In this invention, the deposition method preferably includes magnetron sputtering or pulsed laser deposition, more preferably magnetron sputtering. In this invention, the magnetron sputtering is preferably DC magnetron sputtering. In this invention, the purity of the B4C target used for magnetron sputtering to deposit the B4C layer is preferably 99-99.8%, more preferably 99.5%; the purity of the Mo target used for magnetron sputtering to deposit the Mo layer is preferably 99.9-99.99%, more preferably 99.99%; the purity of the Y target used for magnetron sputtering to deposit the Y layer is preferably 99.9-99.99%, more preferably 99.99%; and the purity of the Si target used for magnetron sputtering to deposit the Si layer is preferably 99.9-99.999%, more preferably 99.999%. In this invention, when the deposition method is magnetron sputtering, the sputtering power for depositing the B4C layer is preferably 110-130W, more preferably 115-120W; the sputtering power for depositing the Mo layer is preferably 40-60W, more preferably 50-55W; the sputtering power for depositing the Y layer is preferably 10-20W, more preferably 15-18W; and the sputtering power for depositing the Si layer is preferably 90-110W, more preferably 95-100W. In this invention, the sputtering rate for magnetron sputtering of the B4C layer is preferably 0.06–0.15 nm / s, more preferably 0.08 nm / s; the sputtering rate for magnetron sputtering of the Mo layer is preferably 0.12–0.43 nm / s, more preferably 0.28 nm / s; the sputtering rate for magnetron sputtering of the Y layer is preferably 0.08–0.19 nm / s, more preferably 0.14 nm / s; and the sputtering rate for magnetron sputtering of the Si layer is preferably 0.16–0.63 nm / s, more preferably 0.42 nm / s. In this invention, the working gas for magnetron sputtering is preferably argon, and the purity of the argon is preferably 99.999%; the pressure of the working gas is preferably 0.14–0.16 Pa, more preferably 0.15 Pa. In this invention, the base vacuum of the magnetron sputtering is preferably 1.8 × 10⁻⁶. -4 ~2.2×10 -4 Pa, more preferably 2×10 Pa -4 Pa.

[0031] The present invention also provides the application of the extreme ultraviolet light reflector described in the above technical solution or the extreme ultraviolet light reflector prepared by the preparation method described in the above technical solution in an extreme ultraviolet lithography machine.

[0032] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0033] Example 1

[0034] Using a single-crystal silicon wafer (100° orientation) as the substrate, the wafer has a roughness of 0.3 nm. A B4C layer, a Mo layer, a Y layer, and a Si layer are deposited on the surface of the single-crystal silicon wafer by magnetron sputtering. This process is repeated 50 times to obtain an extreme ultraviolet (EUV) reflector. The magnetron sputtering is a DC magnetron sputtering method with a base vacuum of 2 × 10⁻⁶. -4 The DC magnetron sputtering power for the B4C layer was 120 W, with a sputtering rate of 0.08 nm / s; the sputtering power for the Mo layer was 50 W, with a sputtering rate of 0.28 nm / s; the sputtering power for the Y layer was 15 W, with a sputtering rate of 0.14 nm / s; and the sputtering power for the Si layer was 100 W, with a sputtering rate of 0.42 nm / s. The working gas for DC magnetron sputtering was 99.999% pure argon, and the working gas pressure was 0.15 Pa. The magnetron sputtering was performed using... The purity of the B4C target is 99.5%, the purity of the Mo target for magnetron sputtering is 99.99%, the purity of the Y target for magnetron sputtering is 99.99%, and the purity of the Si target for magnetron sputtering is 99.999%. The thickness of the B4C layer is 0.50 nm, the thickness of the Mo layer is 2.24 nm, the thickness of the Y layer is 0.50 nm, and the thickness of the Si layer is 3.69 nm, that is, the thickness of the periodic unit is 6.93 nm; the thickness of the multilayer film material is 346.5 nm.

[0035] Comparative Example 1

[0036] An extreme ultraviolet reflector was prepared according to the method of Example 1, except that the order in which the multilayer film material was deposited on the substrate surface was Y layer, Mo layer, B4C layer and Si layer.

[0037] Comparative Example 2

[0038] An extreme ultraviolet reflector was prepared according to the method in Example 1, except that the roughness of the single-crystal silicon wafer was 0.8 nm.

[0039] Comparative Example 3

[0040] The extreme ultraviolet reflector was prepared according to the method of Example 1, except that only the Mo layer and Si layer were used in the process of depositing multilayer film material on the substrate surface, without the Y layer and B4C layer.

[0041] The reflectance curves of the extreme ultraviolet reflectors prepared in Example 1 and Comparative Examples 1-3 were simulated using IMD software, as shown below. Figure 2 As shown in Table 1, the theoretical reflectivity of the extreme ultraviolet reflectors prepared in Example 1 and Comparative Examples 1-3 was calculated based on the reflectivity curves.

[0042] Table 1. Theoretical reflectivity of the extreme ultraviolet light reflecting mirrors prepared in Example 1 and Comparative Examples 1-3

[0043] Example Theoretical reflectance (%) Example 1 74.33 Comparative Example 1 72.22 Comparative Example 2 70.98 Comparative Example 3 74.06

[0044] Combining Table 1 and Figure 2 It is evident that the extreme ultraviolet (EUV) reflector provided by this invention improves the theoretical reflectivity compared to existing EUV reflectors. Comparing the results of Example 1 and Comparative Example 1, it is clear that the stacking order of the B4C, Mo, Y, and Si layers affects the reflectivity; only by depositing the B4C, Mo, Y, and Si layers on the substrate surface in this order can the theoretical reflectivity of the EUV reflector be improved. Comparing the results of Example 1 and Comparative Example 2, it is clear that only by limiting the substrate roughness to the range of 0.28–0.32 nm can the theoretical reflectivity of the EUV reflector be improved. Comparing the results of Example 1 and Comparative Example 3, it is clear that intercalating a Y layer between the Mo and Si layers, and intercalating a B4C layer between the Si and Mo layers, can suppress diffusion between the Mo and Si layers, thereby improving the boundary clarity of the Mo and Si layers in the multilayer film material and increasing the reflectivity of the EUV reflector for EUV light.

[0045] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A multilayer film material comprising stacked periodic units, wherein the periodic unit comprises sequentially stacked B4C layers, Mo layers, Y layers and Si layers; the two sides of the multilayer film material are B4C layers and Si layers, respectively; the multilayer film material is prepared by magnetron sputtering. In one periodic cell, the thickness of the B4C layer is 0.48~0.52nm, the thickness of the Mo layer is 2.22~2.26nm, the thickness of the Y layer is 0.48~0.52nm, and the thickness of the Si layer is 3.67~3.71nm.

2. The multilayer film material according to claim 1, characterized in that, The thickness of a single periodic cell is 6.9~6.98 nm.

3. The multilayer film material according to claim 1 or 2, characterized in that, The number of periodic units is 40 to 60.

4. An extreme ultraviolet (EUV) reflector, comprising a substrate and a multilayer film on the substrate surface, characterized in that, The multilayer film is composed of the multilayer film material according to any one of claims 1 to 3; the substrate surface is in direct contact with the B4C layer in the multilayer film.

5. The extreme ultraviolet light reflector according to claim 4, characterized in that, The substrate includes a monocrystalline silicon wafer, quartz, or K9 glass; The roughness of the substrate is 0.28~0.32nm.

6. The method for preparing the extreme ultraviolet reflector according to claim 4 or 5, comprising the following steps: A B4C layer, a Mo layer, a Y layer and a Si layer are sequentially deposited on the substrate surface to form a periodic unit, and the periodic unit is repeatedly deposited to form a multilayer film.

7. The preparation method according to claim 6, characterized in that, The deposition methods include magnetron sputtering or pulsed laser deposition.

8. The preparation method according to claim 7, characterized in that, When the deposition method is magnetron sputtering, the sputtering power for depositing the B4C layer is 110~130W, the sputtering power for depositing the Mo layer is 40~60W, the sputtering power for depositing the Y layer is 10~20W, and the sputtering power for depositing the Si layer is 90~110W.

9. The application of the extreme ultraviolet reflector according to claim 4 or 5 or the extreme ultraviolet reflector prepared by the preparation method according to any one of claims 6 to 8 in an extreme ultraviolet lithography machine.

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