阅读说明：本技术 图案化装置 (Patterning device ) 是由 M·A·范德凯克霍夫 L·C·德温特 E·范塞腾 于 2018-05-02 设计创作，主要内容包括：一种用于与光刻设备一起使用的图案化装置,该装置包括：被配置为吸收入射辐射并且反射部分入射辐射的吸收器部分,吸收器部分包括第一层和第二层,吸收器部分的第一层包括第一材料,该第一材料与吸收器部分的第二层的第二材料不同；被布置在吸收器部分下方的反射器部分,反射器部分被配置为反射入射辐射；以及被布置在反射器部分与吸收器部分之间的相位调谐部分,相位调谐部分被配置为在由反射器部分反射的辐射与由吸收器部分反射的部分辐射之间引起相移,使得由反射器部分反射的辐射与由吸收器部分反射的部分辐射相消干涉。(A patterning device for use with a lithographic apparatus, the device comprising: an absorber portion configured to absorb incident radiation and reflect a portion of the incident radiation, the absorber portion comprising a first layer and a second layer, the first layer of the absorber portion comprising a first material that is different from a second material of the second layer of the absorber portion; a reflector portion disposed below the absorber portion, the reflector portion configured to reflect incident radiation; and a phase tuning portion disposed between the reflector portion and the absorber portion, the phase tuning portion configured to induce a phase shift between radiation reflected by the reflector portion and a portion of the radiation reflected by the absorber portion such that the radiation reflected by the reflector portion destructively interferes with the portion of the radiation reflected by the absorber portion.)

1. A patterning device for use with a lithographic apparatus, the device comprising:

an absorber portion configured to absorb incident radiation and reflect a portion of the incident radiation, the absorber portion comprising a first layer and a second layer, the first layer of the absorber portion comprising a first material that is different from a second material of the second layer of the absorber portion,

a reflector portion disposed below the absorber portion, the reflector portion configured to reflect incident radiation; and

a phase tuning portion disposed between the reflector portion and the absorber portion, the phase tuning portion configured to induce a phase shift between radiation reflected by the reflector portion and a portion of radiation reflected by the absorber portion such that radiation reflected by the reflector portion destructively interferes with the portion of radiation reflected by the absorber portion.

2. The apparatus of claim 1, wherein the phase tuning portion comprises a material and/or thickness selected such that the phase shift caused by the phase tuning portion causes destructive interference between radiation reflected by the reflector portion and a portion of radiation reflected by the absorber portion.

3. The device of claim 1 or 2, wherein the first material comprises one or more optical properties different from one or more properties of the second material.

4. The device of any preceding claim, wherein the first and second materials are selected such that the reflectivity of the absorber portion is lower than the reflectivity of the reflector portion.

5. The apparatus of any one of the preceding claims, wherein the first material and the second material are selected such that the absorber portion comprises a reflectivity in a range of about 1% to 20%.

6. The apparatus of any preceding claim, wherein the first and second materials are selected such that the thickness of the absorber portion is equal to or less than 25nm or 30 nm.

7. The apparatus of any one of the preceding claims, wherein the absorber portion comprises a plurality of first layers and a plurality of second layers.

8. The apparatus of claim 7, wherein the/each first layer of the plurality of first layers is alternately arranged with the/each second layer of the plurality of second layers.

9. The apparatus of any preceding claim, wherein the/each first layer and the/each second layer are arranged such that the portion of radiation partially reflected by the absorber is in phase or comprises a single phase.

10. A device according to any preceding claim, wherein the first material of the/each first layer comprises a refractive index and/or absorption coefficient which is higher than that of the second material of the/each second layer.

11. The apparatus of any one of claims 7 to 10, wherein the number of first and second layers is selected to provide a predetermined reflectivity of the absorber portion.

12. The device of any preceding claim, wherein the ratio of the thickness of the first and second materials and/or the first layer to the thickness of the second layer is selected to provide a predetermined reflectivity.

13. An apparatus as claimed in any preceding claim, wherein the phase tuning portion comprises the same material as the first material of the/each first layer or the second material of the/each second layer or the reflector portion.

14. An apparatus as claimed in any one of claims 1 to 12, wherein the phase tuning portion comprises a material different from the first material of the/each first layer and/or the second material of the/each second layer.

15. The apparatus of any one of the preceding claims, wherein the absorber comprises a third layer and a fourth layer.

16. The apparatus of claim 15, wherein one of the third layer or the fourth layer is disposed on one of the first layer or the second layer and the other of the third layer or the fourth layer is disposed on the one of the third layer or the fourth layer disposed on the one of the first layer or the second layer.

17. The device of claim 15 or 16, wherein the first layer and/or the fourth layer comprise at least one of silver, tantalum nitride, and nickel.

18. The device of any one of claims 15 to 17, wherein the second layer and/or the third layer comprise at least one of aluminum and silicon.

19. The apparatus of any preceding claim, wherein the phase tuning portion comprises at least one of ruthenium, silicon and molybdenum.

20. The apparatus of any preceding claim, wherein the absorber portion is arranged on the phase tuning portion and/or the reflector portion to form a pattern to be projected on a substrate by a lithographic apparatus.

21. The device according to any of the preceding claims, wherein the device is provided for use with radiation having a wavelength of about 13.5nm or about 6.7 nm.

22. A method of manufacturing a patterning device for use with a lithographic apparatus, the method comprising:

forming a reflector portion configured to reflect incident radiation;

forming an absorber portion configured to absorb incident radiation and reflect a portion of the incident radiation, wherein the reflector portion is formed below the absorber portion, the absorber portion comprising a first layer and a second layer, the first layer comprising a first material different from a second material of the second layer; and

forming a phase tuning portion between the reflector portion and the absorber portion, the phase tuning portion configured to induce a phase shift between radiation reflected by the reflector portion and a portion of radiation reflected by the absorber portion such that radiation reflected by the reflector portion destructively interferes with the portion of radiation reflected by the absorber portion.

23. Use of a patterning device according to any of claims 1 to 21 with a lithographic apparatus.

24. A method comprising projecting a patterned beam of radiation onto a substrate, wherein the beam of radiation is patterned by a patterning device according to any one of claims 1 to 21.

Technical Field

The present invention relates to a patterning device for use with a lithographic apparatus and a method of manufacturing the patterning device.

Background

A lithographic apparatus is a machine that is configured to apply a desired pattern onto a substrate. Lithographic apparatus can be used, for example, in the manufacture of Integrated Circuits (ICs). The lithographic apparatus can, for example, project a pattern from a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (resist) provided on the substrate.

The wavelength of radiation used by the lithographic apparatus to project a pattern onto a substrate determines the minimum size of features that can be formed on the substrate. Lithographic apparatus using EUV radiation (electromagnetic radiation having a wavelength in the range of 4-20 nm) may be used to form features on a substrate that are smaller than conventional lithographic apparatus (e.g. electromagnetic radiation having a wavelength of 193nm may be used).

The patterning device may be provided in the form of a binary mask comprising a substrate with a reflective part and an absorbing part on top. The absorbing portion may comprise a thickness of about 60 to 70 nm. Such a thickness of the absorbing portion may be problematic for the performance of the lithographic apparatus. The size of the features to be imaged may be small relative to the thickness of the absorbing portion, which may lead to complex three-dimensional diffraction or shadowing effects. For example, due to the angle of incidence (which may be non-zero) of EUV radiation on the patterning device, a large difference between horizontal and vertical lines, so-called H-V difference, may be observed on the substrate. In addition, the absorbing portion may introduce non-telecentricity to the radiation projected by the patterning device.

Disclosure of Invention

According to a first aspect of the invention, there is provided a patterning device for use with a lithographic apparatus, the device comprising: an absorber portion configured to absorb incident radiation and reflect a portion of the incident radiation, the absorber portion comprising a first layer and a second layer, the first layer of the absorber portion comprising a first material that is different from a second material of the second layer of the absorber portion; a reflector portion disposed below the absorber portion, the reflector portion configured to reflect incident radiation; and a phase tuning portion disposed between the reflector portion and the absorber portion, the phase tuning portion configured to induce a phase shift between radiation reflected by the reflector portion and a portion of the radiation reflected by the absorber portion such that the radiation reflected by the reflector portion destructively interferes with the portion of the radiation reflected by the absorber portion.

By providing the absorber portion with a first layer comprising a first material different from a second material of the second layer, the reflectivity of the absorber portion may be varied. This allows the thickness of the absorber section to be reduced relative to an absorber section comprising a single material.

The phase tuning portion may comprise a material and/or thickness selected such that the phase shift caused by the phase tuning portion may cause destructive interference between radiation reflected by the reflector portion and a portion of radiation reflected by the absorber portion.

The first material may include one or more optical properties that are different from one or more properties of the second material.

The first material and the second material may be selected such that the reflectivity of the absorber portion may be lower than the reflectivity of the reflector portion.

The first material and the second material may be selected such that the absorber portion may include a reflectivity in a range of about 1% to 20%.

The first material and the second material may be selected such that the thickness of the absorber portion may be equal to or less than 25nm or 30 nm. By selecting the first material and the second material such that the thickness of the absorber portion may be equal to or less than 25nm or 30nm, shadowing or non-telecentricity effects may be reduced, which may improve the performance of the lithographic apparatus.

The absorber portion may include a plurality of first layers and/or a plurality of second layers.

The/each first layer of the plurality of first layers may be alternately arranged with the/each second layer of the plurality of second layers.

The first layer/each first layer and the second layer/each second layer may be arranged such that the portion of the radiation partially reflected by the absorber may be in-phase, e.g. substantially in-phase, or comprise a single phase.

The refractive index and/or absorption coefficient of the first material of the/each first layer may be higher than the refractive index and/or absorption coefficient of the second material of the/each second layer.

The number of first and second layers may be selected to provide a predetermined reflectivity of the absorber portion.

The ratio of the thickness of the first and second materials and/or the first layer to the thickness of the second layer may be selected to provide a predetermined reflectivity.

The material of the phase tuning section may be the same as the first material of the/each first layer or the second material of the/each second layer or the material of the reflector section. This may facilitate the fabrication of the patterning device.

The material of the phase tuning section may be different from the first material of the/each first layer and/or the second material of the/each second layer.

The absorber may include a third layer and a fourth layer.

One of the third layer or the fourth layer may be disposed on one of the first layer or the second layer. The other of the third layer or the fourth layer may be disposed on the above-mentioned one of the third layer or the fourth layer disposed on the above-mentioned one of the first layer or the second layer.

The first layer and/or the fourth layer may include at least one of silver, tantalum nitride, and nickel.

The second layer and/or the third layer may include at least one of aluminum and silicon.

As described above, by providing the third layer and/or the fourth layer to the absorber portion, one or more characteristics of the patterning device, e.g., the absorber portion, may be adjusted. For example, the provision of the third and/or fourth layer of the absorber portion may improve the stability/performance of the patterning device under the load imposed on the patterning device by the radiation and/or hydrogen environment of the lithographic apparatus. The provision of the third and/or fourth layer may facilitate cleaning and/or inspection of the patterning device, for example deep ultraviolet inspection.

The phase tuning part may include at least one of ruthenium, silicon, and molybdenum.

The absorber portion may be arranged on the phase tuning portion and/or the reflector portion to form a pattern to be projected on the substrate by the lithographic apparatus.

A patterning device may be provided for use with radiation including wavelengths of about 13.5nm or about 6.7 nm.

According to a second aspect of the invention, there is provided a method of manufacturing a patterning device for use with a lithographic apparatus, the method comprising: forming a reflector portion configured to reflect incident radiation; forming an absorber portion configured to absorb incident radiation and reflect a portion of the incident radiation, wherein the reflector portion is formed below the absorber portion, the absorber portion comprising a first layer comprising a first material and a second layer, the first material being different from a second material of the second layer; and forming a phase tuning section between the reflector section and the absorber section, the phase tuning section configured to induce a phase shift between the radiation reflected by the reflector section and the portion of the radiation reflected by the absorber section such that the radiation reflected by the reflector section destructively interferes with the portion of the radiation reflected by the absorber section.

According to a third aspect of the invention, there is provided a patterning device according to the first aspect for use in conjunction with a lithographic apparatus.

According to a fourth aspect of the invention, there is provided a method comprising projecting a patterned beam of radiation onto a substrate, wherein the beam of radiation is patterned by a patterning device according to the first aspect.

Various aspects and features of the invention set forth above or below may be combined with various other aspects and features of the invention that will be apparent to those skilled in the art.

Drawings

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which:

FIG. 1 depicts a lithographic system comprising a lithographic apparatus and a patterning device according to an embodiment of the invention;

fig. 2 schematically depicts a patterning device according to an embodiment of the invention;

FIG. 3 depicts a graph of the reflectivity of the absorber portion of the patterning device according to an embodiment of the invention;

FIG. 4 depicts a graph of the reflectivity of the absorber portion of the patterning device according to an embodiment of the invention;

fig. 5 depicts a graph of the reflectivity of an absorber portion of a patterning device according to another embodiment of the invention;

fig. 6 depicts a graph of the reflectivity of an absorber portion of a patterning device according to another embodiment of the invention;

fig. 7 schematically depicts a patterning device according to an embodiment of the invention; and

fig. 8 depicts a flow chart of a method of manufacturing a patterning device according to an embodiment of the invention.

Detailed Description

FIG. 1 depicts a lithographic system including a patterning device MA according to one embodiment of the invention. The lithographic system comprises a radiation source SO and a lithographic apparatus LA. The radiation source SO is configured to generate a beam B of Extreme Ultraviolet (EUV) radiation. The lithographic apparatus LA comprises an illumination system IL, a support structure MT configured to support a patterning device MA, a projection system PS, and a substrate table WT configured to support a substrate W. The illumination system IL is configured to condition the radiation beam B before it is incident on the patterning device MA. The projection system is configured to project the radiation beam B (which has now been patterned by the mask MA) onto the substrate W. The substrate W may include a previously formed pattern. In this case, the lithographic apparatus aligns the patterned radiation beam B with a pattern previously formed on the substrate W.

The source SO, the illumination system IL and the projection system PS may all be constructed and arranged such that they are isolated from the external environment. A gas (e.g., hydrogen) at a pressure below atmospheric pressure may be provided in the radiation source SO. A vacuum may be provided in the illumination system IL and/or the projection system PS. A small amount of gas (e.g. hydrogen) at a pressure substantially below atmospheric pressure may be provided in the illumination system IL and/or the projection system PS.

The radiation source SO shown in fig. 1 is of a type that may be referred to as a Laser Produced Plasma (LPP) source. Laser 1 (which may be, for example, CO)₂A laser) is arranged to deposit energy via a laser beam 2 into a fuel such as tin (Sn) provided from a fuel emitter 3. Although tin is mentioned in the following description, any suitable fuel may be used. The fuel may for example be in liquid form and may for example be a metal or an alloy. The fuel emitter 3 may comprise a nozzle, e.g. in the form of droplets, configured to direct tin along a trajectory towards the plasma formation region 4. The laser beam 2 is incident on the tin at the plasma formation region 4. The deposition of laser energy in the tin generates a plasma 7 at the plasma formation region 4. During deenergization and recombination of ions of the plasma, radiation, including EUV radiation, is emitted from the plasma 7.

EUV radiation is collected and focused by a near normal incidence radiation collector 5 (sometimes more generally referred to as a normal incidence radiation collector). The collector 5 may have a multilayer structure arranged to reflect EUV radiation (e.g. EUV radiation having a desired wavelength such as 13.5 nm). The collector 5 may have an elliptical configuration with two elliptical foci. As described below, the first focus may be at the plasma formation region 4 and the second focus may be at the intermediate focus 6.

The laser 1 may be remote from the radiation source SO. In this case, the laser beam 2 may be delivered from the laser 1 to the radiation source SO by means of a beam delivery system (not shown) comprising, for example, suitable directing mirrors and/or a beam expander, and/or other optics. The laser 1 and the radiation source SO may together be considered a radiation system.

The radiation reflected by the collector 5 forms a radiation beam B. The radiation beam B is focused at point 6 to form an image of the plasma formation region 4, which plasma formation region 4 serves as a virtual radiation source for the illumination system IL. The spot 6 at which the radiation beam B is focused may be referred to as intermediate focus. The radiation source SO is arranged such that the intermediate focus 6 is located at or near an opening 8 in a closed structure 9 of the radiation source.

The radiation beam B enters the illumination system IL from a radiation source SO, and the illumination system IL is configured to condition the radiation beam. The illumination system IL may comprise a facetted field lens device 10 and a facetted pupil lens device 11. Together, the multi-facet field lens arrangement 10 and the multi-facet pupil lens arrangement 11 provide the radiation beam B with a desired cross-sectional shape and a desired angular intensity distribution. The radiation beam B passes from the illumination system IL and is incident on the patterning device MA, which is held by the support structure MT. The patterning device MA reflects and patterns the radiation beam B. The illumination system IL may comprise other mirrors or devices in addition to or instead of the multi-surface field lens device 10 and the multi-surface pupil lens device 11.

After reflection from the patterning device MA, the patterned radiation beam B enters the projection system PS. The projection system comprises a plurality of mirrors 13, 14 configured to project the radiation beam B onto a substrate W held by the substrate table WT. The projection system PS may apply a reduction factor to the beam of radiation so as to form an image having features smaller than corresponding features on the patterning device MA. For example, a reduction factor of 4 may be applied. Although the projection system PS has two mirrors in fig. 1, the projection system may include any number of mirrors (e.g., six mirrors).

The radiation source SO shown in fig. 1 may comprise components not shown. For example, a spectral filter may be provided in the radiation source. The spectral filter may be substantially transmissive for EUV radiation but substantially blocking for other wavelengths of radiation, such as infrared radiation.

FIG. 2 schematically depicts a patterning device MA for use with a lithographic apparatus according to an embodiment of the invention. The patterning device MA may be provided in the form of a mask MA, for example an EUV mask. The mask MA comprises an absorber portion 16 configured to absorb incident radiation B and to reflect part of the incident radiation. The mask MA comprises a reflector portion 18 arranged below the absorber portion 16. The reflector portion 18 is configured to reflect incident radiation. The mask MA may include a phase tuning section 20 disposed between the reflector section 18 and the absorber section 16. The phase tuning section 20 is then configured to induce a phase shift between the radiation reflected by the reflector section 18 and the portion of the radiation reflected by the absorber section 16 such that the radiation reflected by the reflector section 18 destructively interferes with the portion of the radiation reflected by the absorber section 16. The provision of the phase tuning section 20 may allow a reduction in the thickness of the absorber section 20. This in turn may reduce shadowing effects and/or non-telecentric effects.

The term "radiation" can be considered to include at least a portion or all of a radiation beam. The term "radiation" may be used interchangeably with the term "radiation beam".

The phase shift caused by the phase tuning section may be or comprise a 180 ° phase shift. Radiation reflected by the reflector portion 18 may pass through the phase tuning portion 20 and the absorber portion 16, for example, before destructively interfering with a portion of the radiation reflected by the absorber portion 16.

The reflector portion 18 may comprise a multilayer structure. The reflector portion 18 may comprise a plurality of layers. The reflector portion may comprise pairs of layers 18 a. Each pair of layers 18a includes a first layer 18b having a first material and a second layer 18c having a second material. The first material of the first layer 18b may be different from the second material of the second layer 18 c. The first material may include one or more optical properties that are different from one or more properties of the second material. For example, the first material may comprise a refractive index and/or absorption coefficient that is lower than the refractive index and/or absorption coefficient of the second material. The first material may be considered to comprise an optical impedance that is lower than the optical impedance of the second material. By providing the reflector portion with a first layer comprising a first material different from a second material of the second layer, the reflectivity of the reflector portion may be varied. The pairs of layers 18a are arranged on top of each other such that the first layers 18b and the second layers 18c are arranged alternately. The first material may include silicon and/or beryllium. The second material may comprise molybdenum and/or ruthenium. In embodiments where the first material comprises silicon and the second material comprises molybdenum, the reflector portion 18 may comprise a reflectivity of approximately 70%.

The reflector portion 18 may be disposed on a substrate 22, and the substrate 22 may include a glass substrate.

The phase tuning section 20 may comprise a material selected such that the phase shift caused by the phase tuning section causes destructive interference between radiation reflected by the reflector section 18 and a portion of radiation reflected by the absorber section 16. The phase tuning section 20 may comprise silicon. It should be understood that the phase tuning portion disclosed herein is not limited to including silicon, and in other embodiments, one or more other materials may be used. For example, in other embodiments, the phase tuning section may include molybdenum and/or ruthenium.

The mask MA may comprise a protective layer 21. The protective layer 21 may be considered as a neutral layer. In other words, the protective layer 21 may allow the order of the layers (e.g., the first layer 18b and the second layer 18c) of the reflector portion 18, and/or the order of one or more layers of the absorber portion 16 (to be described below) to be changed or altered. This may allow tuning or altering the phase between the radiation reflected by the reflector portion 18 and the portion of the radiation reflected by the absorber portion 16, for example, such that the radiation reflected by the reflector portion 18 destructively interferes with the portion of the radiation reflected by the absorber portion 16. The protective layer 21 may be arranged on the reflector portion 18, such as between the reflective portion 18 and the phase tuning portion 20. The protective layer may be considered to be a cover layer of the reflector portion 18. The protective layer 21 may comprise a chemically stable material. For example, the protective layer 21 may include ruthenium.

The protective layer 21 may be considered as part of the phase tuning section 20. For example, the protective layer 21 may comprise a material selected such that the phase shift caused by the phase tuning portion 20 causes destructive interference between radiation reflected by the reflector portion 18 and a portion of radiation reflected by the absorber portion 16. In other words, one or more optical characteristics of the protective layer 21 may be taken into account when selecting the material of the phase tuning section 20.

Although fig. 2 depicts the protective layer 21 disposed between the reflector portion 18 and the phase tuning portion 20, it should be understood that in other embodiments, the protective layer may define or include the phase tuning portion. In other words, the protective layer may be configured to induce a phase shift between the radiation reflected by the reflector portion and the portion of the radiation reflected by the absorber portion such that the radiation reflected by the reflector portion destructively interferes with the portion of the radiation reflected by the absorber portion. In the example in which the protective layer includes ruthenium, the thickness of the protective layer may be increased as compared with the thickness of the protective layer in the example in which the phase tuning portion is provided in addition to the protective layer.

The phase tuning section 20 may include a thickness a selected such that the phase shift caused by the phase tuning section 20 causes destructive interference between radiation reflected by the reflector section 18 and a portion of radiation reflected by the absorber section 16. In embodiments in which the mask MA comprises a phase tuning portion 20 and a protective layer 21, the thickness of the phase tuning portion 20 may be in the range of about 2nm to 5 nm. The protective layer 21 may comprise a thickness of about 2 to 5 nm. At a thickness of about 2 to 5nm, the absorption of the protective layer 21 may be considered reduced, low or negligible. It should be understood that the protective layers disclosed herein are not limited to including thicknesses of about 2nm to 5nm, and in other embodiments, the protective layers may include thicknesses greater than or less than 2nm to 5 nm. For example, in embodiments in which the protective layer defines the phase tuning portion, the thickness of the protective layer 21 may be greater than 2nm to 5 nm.

The absorber section 16 may comprise a multi-layer absorber. For example, the absorber section 16 includes a first layer 16a and a second layer 16 b. The first layer 16a of the absorber portion comprises a first material different from the second material of the second layer 16 b. The first material may include one or more optical properties that are different from one or more properties of the second material. For example, the first material may include a refractive index and/or absorption coefficient that is higher than a refractive index and/or absorption coefficient of the second material. The first material may be considered to comprise an optical impedance that is higher than the optical impedance of the second material. By providing the absorber portion with a first layer comprising a first material different from a second material of the second layer, the reflectivity of the absorber portion may be changed. In addition, the thickness of the absorber portion may be reduced relative to an absorber portion comprising a single material.

The first material and the second material may be selected such that the reflectivity of the absorber portion is lower than the reflectivity of the reflector portion. For example, the first material and the second material may be selected such that the reflectivity of the absorber portion is a fraction, such as a well-defined fraction, of the reflectivity of the reflector portion. The first and second materials may be selected such that the absorber portion 16 includes a reflectivity in a range of about 1% to 20% (e.g., 5% to 15%). The first and second materials may be selected based on one or more optical properties of the first and second materials. For example, the first and second materials may be selected such that there is an optical contrast or difference between the first and second layers 16a, 16 b. The optical contrast or difference between the first material and the second material may also determine the reflectivity of the absorber portion 16. For example, the first and second materials may be selected such that there is a difference between the refractive indices (e.g., the real and/or imaginary parts of the refractive indices) of the first and second materials.

The selection of the first and second materials of the first and second layers 16a, 16b may allow the reflectivity of the absorber portion 16 to be varied or tuned, as will be explained below. The first material and the second material may be selected such that the thickness of the absorber portion 16 is equal to or less than 25nm or 30 nm. For example, the first and second materials may be selected such that the thickness of the absorber portion is in the range of about 10nm to 25nm, while the resulting reflectivity of the absorber portion is in the range of 1% to 20%. By providing a mask with an absorber portion having a thickness equal to or less than 25nm or less than 30nm, shadowing or non-telecentricity effects may be reduced, which may improve the performance of the lithographic apparatus.

As shown in fig. 2, the absorber section 16 may include a plurality of first layers 16a and a plurality of second layers 16 b. Each of the plurality of first layers is alternately arranged with each of the plurality of second layers 16 b. The/each first layer 16a and second layer 16b may form a pair of layers 16 c. In the embodiment shown in fig. 2, four pairs of layers 16c are stacked on top of each other. It should be understood that in other embodiments, the absorber portion 16 may include more or less than four pairs of layers. For example, as will be explained below, the number of layer pairs may be reduced or increased to change or tune the reflectivity of the absorber portion 16.

The first layer 16 a/each first layer 16a and the second layer/each second layer 16b may be arranged such that the part of the radiation reflected by the absorber portion 16 is in phase or comprises a single phase. The sum of the thickness of the first layer and the thickness of the second layer may correspond to N times about half the wavelength λ of the radiation (e.g., λ/2 × N, where N ═ 1, 2, 3 … …). For example, in embodiments where the radiation includes a wavelength λ of 13.5nm, the sum of the thicknesses of the first and second layers 16a, 16b may be about 7nm or N times 7nm (e.g., 7nm x N). It should be understood that in other embodiments, the radiation may include a wavelength of about 6.7 nm. In such embodiments, the sum of the thicknesses of the first and second layers may be about 3nm or N times 3nm (e.g., 3nm N). It will be appreciated that the exact thickness of each or both of the first and second layers may depend on the phase shift introduced into the radiation at the interface between the first and second layers.

The first layer 16 a/each first layer 16a and the second layer 16 b/each second layer 16b may be arranged such that part of the radiation reflected by the absorber portion 16 is reflected at least at an interface between the first layer 16 a/each first layer 16a and the second layer 16 b/each second layer 16 b. The remainder of the incident radiation may be absorbed by the absorber portion 16. The absorber portion 16 can be configured to include an absorption rate of about 85% to 95% (e.g., about 98%). In the embodiment shown in fig. 2, the first material of the first layer 16a comprises silver and the second material of the second layer 16b comprises aluminum. In the embodiment of fig. 2, a second layer 16b comprising a second material is arranged on the phase tuning part 20, followed by a first layer 16a comprising a first material. It should be understood that in other embodiments, a first layer comprising a first material may be disposed on the phase tuning portion.

Fig. 3 depicts a graph of the simulated reflectivity of the absorber portion 16 depending on the thickness of the phase tuning portion 20 (comprising silicon in this embodiment) and the ratio between the thickness of the first layer 16a and the thickness of the second layer 16 b. For an absorber portion in which the first material of the first layer 16a comprises silver and the second material of the second layer 16b comprises aluminum, the reflectivity of the absorber portion 16 is obtained. As can be seen from fig. 3, the reflectivity of the absorber portion 16 is reduced by increasing the thickness of the first layer 16a relative to the thickness of the second layer 16b, and/or the reflectivity of the absorber portion 16 is increased by reducing the thickness of the first layer 16a relative to the thickness of the second layer 16 b. This may be due to the material of the first layer 16a having a higher absorption coefficient than the material of the second layer 16 b. However, it should be understood that the material of the first layer is not limited to having a higher absorption coefficient than the material of the second layer. For example, it is understood that an increase or decrease in the thickness of the first layer relative to the thickness of the second layer may cause an increase or decrease in the absorptivity of the first layer relative to the absorptivity of the second layer.

The variation in the thickness of the phase tuning section 20 causes variation in the reflectivity of the absorber section. For example, as shown in fig. 3, an increase in the thickness of the phase tuning section 20 may result in an increase in the reflectivity of the absorber section 16. The thickness of the phase tuning section 20 may be varied instead of or in addition to varying the thickness of the first layer 16a and/or the second layer 16 b. The reflectivity of the absorber portion 16 may be tuned or changed by changing the thickness of the first layer 16a and/or the second layer 16b of the absorber portion 16 and/or the thickness of the phase tuning portion 20. For example, the thickness of the first layer 16a and/or the second layer 16b of the absorber portion 16 and/or the thickness of the phase tuning portion 20 may be selected to provide a predetermined or desired reflectivity of the absorber portion 16. In other words, the ratio of the thickness of the first material to the thickness of the second material may be selected to provide a predetermined or desired reflectivity.

Fig. 4 depicts a graph of simulated reflectance with respect to the absorber portion 16 depicted in fig. 3 as a function of the thickness of the first layer 16a or the second layer 16 b. Each line shown in fig. 4 corresponds to the configuration of the phase tuning section 20, for example, the thickness of the phase tuning section 20. In the graph shown in fig. 4, the thickness of the phase tuning section 20 varies between about 0nm and 5 nm. By reducing the thickness of the first layer 16a or the thickness of the second layer 16b, the reflectivity of the absorber portion 16 increases, and the increase in the thickness of the first layer 16a or the thickness of the second layer 16b causes a decrease in the reflectivity of the absorber portion 16. As described above, a decrease or increase in the thickness of the first layer 16a or the second layer 16b may cause a relative decrease or increase in the absorptivity of the first layer 16a or the second layer 16 b. For example, in an embodiment in which the absorber portion 16 comprises two pairs of layers 16c, each first layer 16a comprises silver, each second layer 16b comprises aluminum, and each of the first and second layers has a thickness of about 3.5nm, the reflectivity of the absorber portion 16 is about 10%. In this embodiment, the thickness of the absorber section 16 is about 14nm, while the thickness of the phase tuning section 20 is about 5 nm.

It should be understood that the number of first and second layers 16a, 16b (e.g., the number of layer pairs 16 c) may be varied to tune or vary the reflectivity of the absorber portion 16. Fig. 5 depicts another graph of simulated reflectivity of the absorber portion 16 depending on the thickness of the first layer 16a or the second layer 16 b. In fig. 5, a simulated reflectivity of an absorber portion similar to that described above with respect to fig. 3 is depicted. However, fig. 5 depicts the simulated reflectance of the absorber portion 16 including three pairs of layers 16c (e.g., three first layers 16a and three second layers 16 b). As can be seen from fig. 5, the absorber portion 16 including three pairs of layers 16c has a reduced reflectivity of the absorber portion 16 compared to the absorber portion 16 including two pairs of layers 16 c. For example, when the thickness of the first layer 16a or the second layer 16a is 3.5nm, the reflectance of the absorber portion 16 is reduced to almost 0%. The number of first and second layers 16a, 16b may be selected to provide a predetermined or desired reflectivity of the absorber portion 16.

Fig. 6 depicts another graph of simulated reflectivity of the absorber portion 16 depending on the thickness of the first layer 16a or the second layer 16 b. In fig. 6, a simulated reflectivity of an absorber portion similar to that described above with respect to fig. 4 is depicted. However, the ratio of the thickness of the first layer 16a to the thickness of the second layer 16b is about 1: 2. in other words, the thickness of the second layer 16b is about twice the thickness of the first layer 16 a. As can be seen from fig. 6, an increase in the thickness of the second layer 16b causes an increase in the reflectivity of the absorber portion 16. For example, when the thickness of the first layer 16a or the second layer 16b is 3.5nm, the reflectance of the absorber portion is greater than 10%.

Fig. 3 to 6 relate to embodiments of the absorber portion 16 comprising silver as the first material of the first layer 16a and aluminum as the second material of the second layer 16 b. It should be understood that the absorber portions described herein are not limited to including a first layer comprising silver and a second layer comprising aluminum. The first and second materials of the first and second layers may be selected to provide a predetermined or desired reflectivity, for example, a predetermined or desired reflectivity of about 5% to 15%. For example, in other embodiments, the first material of the first layer comprises tantalum or tantalum nitride, and/or the second material of the second layer may comprise silicon. The tantalum, tantalum nitride and/or silicon comprise an absorption coefficient that is less than that of silver. By providing tantalum or tantalum nitride as the first material of the first layer and/or silicon as the second material of the second layer, the reflectivity of the absorber portion may be increased relative to an absorber portion comprising silver as the first material of the first layer and aluminum as the second material of the second layer. The absorber portion 16 comprising tantalum or tantalum nitride as the first material of the first layer 16a and/or silicon as the second material of the second layer 16b may have a reflectivity of more than 2% and less than 20%. The reflectivity of the absorber portion 16 may be varied by varying the number of pairs 16c of the first and second layers 16a, 16b and/or the thickness of the first layer 16a relative to the thickness of the second layer 16 b.

FIG. 7 depicts another embodiment of a mask MA for use with a lithographic apparatus.

The mask MA shown in FIG. 7 is similar to the mask MA shown in FIG. 2. In the embodiment shown in fig. 7, the first material of the first layer 16a may comprise silver and the second material of the second layer 16b may comprise silicon. In the embodiment shown in fig. 7, a first layer 16a is arranged on the phase tuning section 20, followed by a second layer 16 b.

In the embodiment depicted in fig. 7, the absorber section 16 further includes a third layer 16d and a fourth layer 16 e. The third layer 16d and the fourth layer 16e may each comprise a material different from the first material of the first layer 16a and the second material of the second layer 16 b. For example, the third material of the third layer 16d may include aluminum, and the fourth material of the fourth layer 16e may include tantalum nitride. In the embodiment depicted in fig. 7, a third layer 16d is disposed on the first layer 16a, and a fourth layer 16e is disposed on the third layer 16 d. It should be understood that the absorber portions disclosed herein are not limited to such an arrangement of the third and fourth layers. For example, in other embodiments, the fourth layer may be disposed on the first layer, or one of the third and fourth layers may be disposed on the second layer, while the other of the third and fourth layers is disposed on one of the third and fourth layers disposed on the second layer. By providing the third layer and/or the fourth layer to the absorber portion 16, one or more characteristics of the patterning device, e.g., the absorber portion, may be adjusted. For example, the provision of the third and/or fourth layer of the absorber portion may improve the stability/performance of the mask under the load imposed on the mask by the radiation and/or hydrogen environment of the lithographic apparatus. The provision of the third and/or fourth layer may facilitate cleaning and/or inspection of the mask, for example deep ultraviolet inspection.

Fig. 8 depicts a flow chart of a method of manufacturing the mask MA depicted in fig. 2 or 7. The method includes forming reflector portions 18 (step 1005). As mentioned above, the reflector portion 18 is configured to reflect incident radiation B. The method includes forming an absorber section 16. The absorber section 16 is configured to absorb incident radiation B and reflect a portion of the incident radiation B (step 1010). The reflector portion 18 is formed below the absorber portion 16. As described above, the absorber section 16 includes the first layer 16a and the second layer 16 b. The first layer 16a of the absorber portion comprises a first material different from the second material of the second layer 16 b. The absorber section 16 may be formed as a multi-layer absorber section. The method includes forming a phase tuning section 20 between the reflector section and the absorber section (step 1015). The phase tuning section 20 is configured to induce a phase shift between the radiation reflected by the reflector section 18 and the portion of the radiation reflected by the absorber section 16 such that the radiation reflected by the reflector section 18 destructively interferes with the portion of the radiation reflected by the absorber section 16.

The reflector portion 18 may be formed on a substrate such as a glass substrate. The absorber section 16, the reflector section 18, and/or the phase tuning section 20 may be formed by one or more deposition methods, such as chemical vapor deposition.

The absorber section 16 may be arranged on the phase tuning section 20 and/or the reflector section 18. The method may include forming a pattern in the absorber section 16 (step 1020). The pattern formed in the absorber portion 16 can be projected on the substrate by the lithographic apparatus LA. For example, a radiation sensitive material (e.g., resist or photoresist) may be applied to the absorber portion 16. The pattern may be exposed on the absorber portion 16. The exposed areas of the absorber portion 16 may be removed, for example, by etching the absorber layer 16.

Although the phase tuning section 20 is described as comprising a different material than the first material of the/each first layer of the absorber section 16 and/or the second material of the/each second layer, for example ruthenium, it will be appreciated that in other embodiments the phase tuning section may comprise the same material as the first material of the first layer or the second material of the second layer of the absorber section 16 or the reflector section 18. For example, the first layer of the phase tuning section 20, which may comprise ruthenium, may be a cap section, which is considered to be the reflector section 18. For example, the cap portion may become part of the absorber portion 16 when the thickness of at least one layer of the reflector portion 18 (e.g., the top or last layer of the reflective layer 18) increases or decreases. At least one layer of the reflector portion may then define the phase tuning portion 20 (or at least a portion thereof). At least one layer of the reflector portion may comprise silicon. In other words, the phase tuning section may be provided by one or more layers adjacent to the cover section. This may facilitate the manufacture of the mask MA.

Although specific reference may be made in this text to embodiments of the invention in the context of lithographic apparatus, embodiments of the invention may be used in other apparatus. Embodiments of the invention may be used in a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or processes an object such as a wafer (or other substrate) or a mask (or other patterning device). These devices may be generally referred to as lithographic tools. Such a lithography tool may use vacuum conditions or ambient (non-vacuum) conditions.

The term "EUV radiation" may be considered to include electromagnetic radiation having a wavelength in the range of 4nm-20nm (e.g., in the range of 13nm-14 nm). The wavelength of the EUV radiation may be less than 10nm, for example in the range 4nm-10nm, such as 6.7nm or 6.8 nm. The mask MA may be provided for use with EUV radiation having a wavelength in the range 13nm-14nm, for example 13.5nm, or in the range 4nm-10nm, for example 6.7nm or 6.8 nm.

Although fig. 1 depicts the radiation source SO as a laser produced plasma LPP source, any suitable source may be used to illustrate EUV radiation. For example, an EUV emitting plasma may be generated by converting a fuel (e.g., tin) into a plasma state using an electrical discharge. This type of radiation source may be referred to as a Discharge Produced Plasma (DPP) source. The discharge may be generated by a power source, which may form part of the radiation source, or may be a separate entity connected via an electrical connection to the radiation source SO.

Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications. Other possible applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, Liquid Crystal Displays (LCDs), thin film magnetic heads, etc.

While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The above description is intended to be illustrative, and not restrictive. Thus, it will be apparent to those skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.