Membrane structure, narrow-band filter and preparation method and application of narrow-band filter

Abstract

The invention provides a film structure for a narrow-band filter, and belongs to the technical field of optical elements. The invention provides a membrane structure for a narrow-band filter. The membrane structure comprises repeated unit layers, each unit layer comprises a strong absorption layer and a space layer which are stacked in sequence; the strong absorption layer is a Ni layer, and the thickness of the strong absorption layer is 1.3 nm; the space layer is a Si layer, and the thickness of the space layer is 5.4 nm; the number of periodic layers of the repeated unit layers is 60. Based on the standing wave principle, the standing wave nodes are designed at the strong absorption layer Ni layer, the filter obtained by the film structure has high working wavelength transmissivity, narrow working bandwidth and high transmission intensity for extreme ultraviolet light, the signal-to-noise ratio of detection or detection equipment is greatly improved, and the close-range working effect can be ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of optical elements, and in particular relates to a membrane structure, a narrow-band filter, and a preparation method and application thereof. Background Art

[0002] A filter is an optical element that separates, selects and adjusts light waves by selectively transmitting or blocking light of a specific frequency or wavelength. Currently, filters are mainly divided into metal filters and thin film filters. Metal filters are made by pressing metal into thin sheets. Because metal materials have only fixed absorption edges, filters made by this method can only filter incident light at or above a certain energy point, and have high selectivity. However, metal filters are not suitable for large-scale applications due to their high cost, heavy weight, sensitivity to mechanical damage and unsatisfactory high-frequency filtering effects. Thin film filters are transmissive thin film filters obtained by coating thin films on soluble materials and dissolving the soluble substances. They have the advantages of simple structure, small size, low cost and high reliability, which makes them a more economical and efficient choice in industrial production. Narrowband filters are filters that are highly selective to light, allowing light of a specific wavelength band to pass through while blocking other wavelength bands, and have high selectivity and transmittance. In the extreme ultraviolet energy region, due to absorption edge and energy reasons, the electromagnetic waves here are absorbed very strongly by the material, resulting in low transmission intensity of the filter in the prior art in the EUV band.

[0003] Therefore, it is necessary to design a narrowband filter serving a specific wavelength, which is not only suitable for the EUV region but also has high transmittance and transmission intensity. Summary of the invention

[0004] The purpose of the present invention is to provide a membrane structure, a narrow-band filter, and a preparation method and application thereof. The narrow-band filter obtained by the membrane structure of the present invention has a high transmittance for the working wavelength of extreme ultraviolet light, a narrow working bandwidth, and a high transmission intensity, which greatly improves the signal-to-noise ratio of the detection or testing equipment, and can also ensure the working effect at a close distance.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: A membrane structure for a narrowband filter comprises repeated unit layers; each unit layer comprises a strong absorption layer and a space layer stacked in sequence; the strong absorption layer is a Ni layer with a thickness of 1.3 nm; the space layer is a Si layer with a thickness of 5.4 nm; the number of periodic layers of the repeated unit layers is 60.

[0006] The present invention also provides a method for preparing the above membrane structure, comprising the following steps: Using Ni target material and Si target material as sputtering target materials, magnetron sputtering is alternately performed on the surface of a substrate to form repeated unit layers on the substrate, and each repeated unit layer includes a Ni layer and a Si layer stacked in sequence.

[0007] Preferably, the magnetron sputtering is performed in an Ar gas atmosphere, and the working gas pressure of the magnetron sputtering is 0.2-0.3 Pa; the magnetron sputtering power of the Ni layer is 110-130 W, and the magnetron sputtering power of the Si layer is 90-110 W.

[0008] The present invention provides a narrow-band filter, comprising the membrane structure described in the above technical solution or the membrane structure prepared by the preparation method described in the above technical solution.

[0009] Preferably, the narrowband filter further includes a cap layer.

[0010] Preferably, the cap layer includes a Ru layer disposed on the surface of the outermost space layer in the membrane structure, and the thickness of the Ru layer is 1-3 nm.

[0011] The present invention also provides a method for preparing the above narrow-band filter, comprising the following steps: A cap layer is deposited on the outermost space layer of the membrane structure by magnetron sputtering.

[0012] Preferably, the magnetron sputtering coating of the cap layer is carried out in an Ar gas atmosphere, and the working gas pressure of the magnetron sputtering coating of the cap layer is 0.2-0.3Pa.

[0013] Preferably, when the cap layer includes a Ru layer, the sputtering power of the Ru layer is 170-190W.

[0014] The present invention also provides the application of the narrow-band filter described in the above technical solution or the preparation method of the narrow-band filter prepared by the preparation method described in the above technical solution in extreme ultraviolet lithography, detection and detection.

[0015] Beneficial effects: The present invention provides a membrane structure for a narrowband filter, comprising repeated unit layers; each unit layer comprises a strong absorption layer and a space layer stacked in sequence; the strong absorption layer is a Ni layer with a thickness of 1.3nm; the space layer is a Si layer with a thickness of 5.4nm; the number of periodic layers of the repeated unit layers is 60. Based on the principle of standing waves, the present invention designs the node of the standing wave at the strong absorption layer Ni layer, at which time the potential energy is the largest, the amplitude of the electric field in the absorption layer is small, and the absorption of the incident radiation is reduced compared with other incident radiation, so the transmittance increases; the peak width affects the filtering effect of the membrane structure, but too small a peak width will also cause the overall transmission signal to decrease. The peak width of the membrane structure of the present invention can reach 0.27nm, the working bandwidth is suitable, and the transmittance is high. The results of the embodiment show that the narrowband filter obtained by the present invention has a maximum peak transmittance of 0.5%~1% and a high transmission efficiency: the width of the main transmission peak of the filter is about 0.27nm, the working bandwidth is about 1.8%, and the working bandwidth is narrow. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments are briefly introduced below.

[0017] Figure 1 is a schematic diagram of the membrane structure; Figure 2 This is a schematic diagram of the standing wave principle of the membrane structure; Figure 3 This is a calculation diagram of the narrow-band transmission peak of the filter obtained in Example 1. DETAILED DESCRIPTION

[0018] The present invention provides a membrane structure for a narrowband filter, comprising repeated unit layers; each unit layer comprises a strong absorption layer and a space layer stacked in sequence; the strong absorption layer is a Ni layer with a thickness of 1.3nm; the space layer is a Si layer with a thickness of 5.4nm; the number of periodic layers of the repeated unit layers is 60.

[0019] In the present invention, the thickness of the strong absorption layer is 1.3 nm, the thickness of the space layer is 5.4 nm, and the optimal ratio (γ) of the strong absorption layer to the total thickness of the strong absorption layer and the space layer is 0.19.

[0020] The present invention also provides a method for preparing the above membrane structure, comprising the following steps: Using Ni target material and Si target material as sputtering target materials, magnetron sputtering is alternately performed on the surface of a substrate to form repeated unit layers on the substrate, and each repeated unit layer includes a Ni layer and a Si layer stacked in sequence.

[0021] In the present invention, the substrate is preferably a soluble substrate; the soluble substrate is preferably a sodium chloride substrate.

[0022] In the present invention, the magnetron sputtering is preferably performed in an Ar atmosphere, and the working pressure of the magnetron sputtering is preferably 0.2-0.3 Pa. In the present invention, DC pulse magnetron sputtering is preferably used, and the coating method is linear target-grabbing coating.

[0023] In the present invention, the magnetron sputtering power of the Ni layer is preferably 110-130W, specifically 120W, and the target material used is a Ni target; the magnetron sputtering power of the Si layer is preferably 90-110W, specifically 100W, and the target material used is a Si target. In the present invention, the allowable thickness error range of each layer of the magnetron sputtering coating is ±0.1nm.

[0024] The present invention provides a narrow-band filter, comprising the membrane structure described in the above technical solution or the membrane structure prepared by the preparation method described in the above technical solution.

[0025] In the present invention, the narrowband filter preferably further includes a cap layer.

[0026] In the present invention, the cap layer preferably further includes a Ru layer disposed on the surface of the outermost space layer in the membrane structure, and the thickness of the Ru layer is preferably 1-3 nm, specifically 2 nm.

[0027] The present invention also provides a method for preparing the above narrow-band filter, comprising the following steps: A cap layer is deposited on the outermost space layer of the membrane structure by magnetron sputtering.

[0028] In the present invention, the magnetron sputtering coating of the cap layer is preferably carried out in an Ar gas atmosphere, and the working gas pressure of the magnetron sputtering coating of the cap layer is preferably 0.2-0.3 Pa, and specifically can be 0.25 Pa.

[0029] In the present invention, when the cap layer preferably includes a Ru layer, the sputtering power of the Ru layer is preferably 170-190 W, specifically 180 W, and the target material used is a Ru target material.

[0030] In the present invention, after completing the magnetron sputtering, it is preferred that the obtained film material is annealed, and the annealing temperature is preferably 150-200°C, specifically 160°C, 180 or 190°C; the annealing holding time is preferably 10-20min, specifically 15min.

[0031] The present invention also provides the application of the narrow-band filter described in the above technical solution or the preparation method of the narrow-band filter prepared by the preparation method described in the above technical solution in extreme ultraviolet lithography, detection and detection.

[0032] In the present invention, the working wavelength of the narrowband filter is preferably 13.5 nm. In the present invention, the electromagnetic wave of 13.5 nm is preferably incident at normal incidence, with an incident angle of 0.

[0033] In order to further illustrate the present invention, the membrane structure and narrow-band filter provided by the present invention are described in detail below in conjunction with the accompanying drawings and embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0034] Example 1 Prepare a soluble substrate (NaCl) for cleaning and drying; Place the substrate into the magnetron sputtering coating equipment and prepare three target materials, namely Ni, Si, and Ru; The Ni sputtering power is 120W, the Si sputtering power is 100W, and the Ru sputtering power is 180W. DC pulse magnetron sputtering is used. The magnetron coating machine is vacuumed to 1.0×10 -4 Pa high vacuum, filled with Ar gas, maintaining a sputtering pressure of 0.25 Pa; Turn on the Ar gas control switch through the program; Run the program, use the linear target coating method, and sequentially coat Ni and Si film materials on the soluble substrate, forming a repeating unit layer on the soluble substrate, with a repeating period of 60 layers; each unit layer includes a Ni layer and a Si layer stacked in sequence, and in each unit layer, the thickness of the Ni layer is 1.3nm, and the thickness of the Si layer is 5.4nm; finally, coat the Ru layer, and the thickness of the Ru layer is 2nm to protect the overall film performance. After the coating is completed, turn off the Ar gas, and complete the film coating after natural cooling; The obtained film is then subjected to low temperature annealing at a temperature of 180° C. for 10 min to obtain a narrow-band filter.

[0035] The working wavelength of the filter prepared in Example 1 is 13.5nm. The electromagnetic wave is incident at normal incidence, the incident angle is 0, the transmission peak width is 0.27nm, the maximum transmission efficiency is about 1%, and the optimal thickness ratio γ is 0.19.

[0036] Figure 1 Schematic diagram of membrane structure.

[0037] Figure 2 Schematic diagram of the standing wave principle of membrane structure.

[0038] Figure 3 The narrow-band transmission peak calculation diagram of the filter obtained in Example 1; Figure 3The results show that the total thickness and thickness ratio of the prepared filter are accurate, the maximum transmittance of the filter is at an operating wavelength of 13.5nm, the maximum transmittance is close to 1%, and the peak width is also moderate. When the wavelength deviates from the operating wavelength of 13.5nm, its transmission efficiency decreases sharply, which can effectively achieve a narrowband filtering effect.

[0039] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A membrane structure for a narrowband filter, characterized in that: It comprises repeated unit layers; each unit layer comprises a strong absorption layer and a space layer stacked in sequence; the strong absorption layer is a Ni layer with a thickness of 1.3 nm; the space layer is a Si layer with a thickness of 5.4 nm; the number of periodic layers of the repeated unit layers is 60.

2. The method for preparing the membrane structure according to claim 1, characterized in that: The following steps are involved: Using Ni target material and Si target material as sputtering target materials, magnetron sputtering is alternately performed on the surface of a substrate to form repeated unit layers on the substrate, and each repeated unit layer includes a Ni layer and a Si layer stacked in sequence.

3. The preparation method according to claim 2, characterized in that: The magnetron sputtering is performed in an Ar gas atmosphere, and the working gas pressure of the magnetron sputtering is 0.2-0.3 Pa; the magnetron sputtering power of the Ni layer is 110-130 W, and the magnetron sputtering power of the Si layer is 90-110 W.

4. A narrowband filter, characterized in that: It includes a membrane structure prepared by the membrane structure according to claim 1 or the preparation method according to any one of claims 2 or 3.

5. The narrowband filter according to claim 4, characterized in that: The narrowband filter further includes a cap layer.

6. The narrowband filter according to claim 5, characterized in that: The cap layer includes a Ru layer disposed on the surface of the outermost space layer in the membrane structure, and the thickness of the Ru layer is 1-3 nm.

7. The method for preparing a narrowband filter according to any one of claims 4 to 6, characterized in that: The following steps are involved: A cap layer is deposited on the outermost space layer of the membrane structure by magnetron sputtering.

8. The preparation method according to claim 7, characterized in that: The magnetron sputtering cap layer is deposited in an Ar atmosphere, and the working pressure of the magnetron sputtering cap layer is 0.2-0.3Pa.

9. The preparation method according to claim 7, characterized in that: When the cap layer includes a Ru layer, the sputtering power of the Ru layer is 170-190W.

10. Use of the narrow-band filter according to any one of claims 4 to 6 or the narrow-band filter prepared by the preparation method according to any one of claims 7 to 9 in extreme ultraviolet lithography, detection and detection.

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