Euv photomask and method of manufacturing the same

Abstract

This disclosure relates to EUV photomasks and methods for manufacturing the same. A method for manufacturing an extreme ultraviolet (EUV) photomask includes: sequentially forming a reflective multilayer stack, a cap layer, an absorber layer, and a hard mask layer on a substrate; forming a photoresist layer on the hard mask layer and patterning the photoresist layer; etching the hard mask layer to form a hard mask; etching the absorber layer to form a patterned absorber layer; removing the patterned photoresist layer and the hard mask; performing a first plasma treatment using a plasma formed from a mixture of oxygen and water; purging the plasma using a mixture of H2 and an inert gas; performing a second plasma treatment using a plasma formed from a mixture of H2 and an inert gas; and performing a wet cleaning operation.

Description

Technical Field

[0001] This disclosure relates to EUV photomasks and methods for manufacturing the same. Background Technology

[0002] Photolithography is one of the key operations in semiconductor manufacturing. Photolithography techniques include ultraviolet (UV) lithography, deep ultraviolet (DUV) lithography, and extreme ultraviolet (EUV) lithography. The photomask is a crucial component in the photolithography process. Importantly, it is essential to fabricate EUV photomasks that achieve high contrast between highly reflective and highly absorbent regions.

[0003] During EUV photomask manufacturing processes, critical dimension losses can occur during mask patterning operations. Oxygen and / or water vapor plasma treatments that help alter the wettability of the mask surface during mask patterning and cleaning operations may result in 1) large critical dimension losses following wet mask cleaning, and 2) oxidation of the ruthenium cap layer, which weakens the cap layer's ability to protect the multilayer from damage. Summary of the Invention

[0004] According to one embodiment of this disclosure, a method for manufacturing an extreme ultraviolet (EUV) mask is provided, comprising: sequentially forming a reflective multilayer stack, a capping layer, an absorption layer, and a hard mask layer on a substrate; forming a photoresist layer on the hard mask layer; patterning the photoresist layer; etching the hard mask layer to form a hard mask; etching the absorption layer to form a patterned absorption layer; removing the patterned photoresist layer and the hard mask; performing a first plasma treatment using a plasma formed from a mixture of oxygen and water; purging the plasma using a mixture of H2 and an inert gas; performing a second plasma treatment using a plasma formed from a mixture of H2 and an inert gas; and performing a wet cleaning operation.

[0005] According to one embodiment of this disclosure, a method for manufacturing a photomask is provided, comprising: forming a multilayer stack of alternating molybdenum and silicon layers on a substrate; forming a capping layer on the multilayer stack; forming an absorption layer on the capping layer; forming a hard mask layer on the absorption layer; patterning the hard mask layer to form a patterned hard mask; extending the pattern in the hard mask into the absorption layer to form a patterned absorption layer, the patterned absorption layer exposing a portion of the capping layer; removing the hard mask; applying a reducing agent to the exposed portions of the patterned absorption layer and the capping layer after removing the hard mask; and performing a wet cleaning operation.

[0006] According to one embodiment of this disclosure, a reflective photomask is provided, comprising: a reflective multilayer stack disposed on a substrate, wherein the reflective multilayer stack includes a plurality of alternating first and second layers; a cap layer disposed on the reflective multilayer stack; and a patterned absorption layer disposed on the cap layer, wherein the reflective photomask has an average extreme ultraviolet radiation reflectance of 65.1 ± 1%. Attached Figure Description

[0007] This disclosure is best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be emphasized that, in accordance with standard practice in the art, the various features are not drawn to scale but are for illustrative purposes only. In fact, for clarity of discussion, the dimensions of the various features may be arbitrarily enlarged or reduced.

[0008] Figure 1 This is a schematic diagram of an EUV lithography system having a laser-generated plasma (LPP) EUV radiation source according to some embodiments of the present disclosure.

[0009] Figure 2 A schematic diagram of an extreme ultraviolet lithography tool according to an embodiment of the present disclosure is shown.

[0010] Figure 3A , Figure 3B , Figure 3C , Figure 3D and Figure 3E An EUV photomask blank according to an embodiment of the present disclosure is shown.

[0011] Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9A , Figure 9B , Figure 10 and Figure 11 A method for manufacturing an EUV photomask according to an embodiment of the present disclosure is illustrated schematically.

[0012] Figure 12 , Figure 13 , Figure 14 , Figure 15 , Figure 16 , Figure 17A , Figure 17B , Figure 18 , Figure 19 , Figure 20 , Figure 21 , Figure 22 and Figure 23 A method for manufacturing an EUV photomask according to an embodiment of the present disclosure is illustrated schematically.

[0013] Figure 24A flowchart illustrating the fabrication of an EUV photomask according to an embodiment of the present disclosure is shown.

[0014] Figure 25 A flowchart illustrating the fabrication of an EUV photomask according to an embodiment of the present disclosure is shown.

[0015] Figure 26 A flowchart illustrating the fabrication of an EUV photomask according to an embodiment of the present disclosure is shown.

[0016] Figure 27 A flowchart illustrating the fabrication of an EUV photomask according to an embodiment of the present disclosure is shown.

[0017] Figure 28A , Figure 28B , Figure 28C and Figure 28D The sequential manufacturing operations of a method for manufacturing a semiconductor device according to embodiments of the present disclosure are illustrated. Detailed Implementation

[0018] It is to be understood that the following disclosure provides many different embodiments or examples for implementing various features of the invention. Specific embodiments or examples of components and arrangements are described below to simplify this disclosure. Of course, these are merely examples and not limiting. For example, the dimensions of elements are not limited to the disclosed range or values, but may depend on process conditions and / or the desired properties of the device. Furthermore, forming a first feature on or over a second feature in the following description may include embodiments where the first and second features are formed in direct contact, and may also include embodiments where an additional feature may be formed between the first and second features such that the first and second features do not need to be in direct contact. For simplicity and clarity, various features may be drawn at any scale.

[0019] Furthermore, for ease of description, this document may use spatially related terms such as “below,” “under,” “down,” “above,” “up,” etc., to describe the relationship between one element or feature as shown in the figure and another element(s) or feature(s). In addition to the orientation depicted in the figure, these spatially related terms are also intended to encompass different orientations of the device in use or operation. The device may be oriented in other ways (rotated 90 degrees or in other directions), and the spatially relative descriptors used herein may be interpreted accordingly. Furthermore, the term “made of” may mean “comprising” or “consisting of.” In this disclosure, the phrase “one of A, B, and C” refers to “A, B, and / or C” (A, B, C, A and B, A and C, B and C, or A, B, and C), and unless otherwise stated, does not refer to an element from A, an element from B, and an element from C.

[0020] Embodiments of this disclosure provide a method for manufacturing an EUV photomask. More specifically, this disclosure provides techniques for improving the contour of circuit patterns formed in the absorption layer of an EUV photomask. Embodiments of this disclosure suppress photomask critical dimension loss during patterning and cleaning operations.

[0021] EUV lithography employs a scanner that uses light from the extreme ultraviolet (EUV) region. The mask is a key component of the EUV lithography system. Because optical materials are opaque to EUV radiation, EUV photomasks are reflective masks. Circuit patterns are formed in an absorption layer, which is disposed on top of the reflective structure. The absorber has low EUV reflectivity, for example, less than 3% to 5%.

[0022] Figure 1 This is a schematic diagram of an EUV lithography system. The EUV lithography system includes: an EUV radiation source device 100 for generating EUV light; an exposure tool 200, such as a scanner; and an excitation laser source device 300. Figure 1 As shown, in some embodiments, the EUV radiation source device 100 and the exposure tool 200 are mounted on the main layer MF of the cleanroom, while the excitation laser source device 300 is mounted in the substrate layer BF below the main layer. The EUV radiation source device 100 and the exposure tool 200 are each placed on base plates PP1 and PP2 via shock absorbers DP1 and DP2, respectively. The EUV radiation source device 100 and the exposure tool 200 are coupled to each other by a coupling mechanism, which may include a focusing unit.

[0023] The EUV lithography system is designed to expose a resist layer using EUV light (or EUV radiation). The resist layer is a material sensitive to EUV light. The EUV lithography system uses an EUV radiation source device 100 to generate EUV light, for example, EUV light with wavelengths ranging from about 1 nm to about 100 nm. In a specific example, the EUV light generated by the EUV radiation source 100 has a center wavelength of about 13.5 nm. In this embodiment, the EUV radiation source 100 utilizes a laser-generated plasma (LPP) mechanism to generate EUV radiation.

[0024] Exposure tool 200 includes various reflective optical components, such as convex / concave / plane mirrors, a mask holding mechanism including a mask stage, and a wafer holding mechanism. EUV radiation generated by EUV radiation source 100 is guided by the reflective optical components onto a mask fixed on the mask stage. In some embodiments, the mask stage includes an electrostatic chuck for holding the mask. Because gas molecules absorb EUV light, the lithography system used for EUV lithography patterning is maintained in a vacuum or low-pressure environment to avoid EUV intensity loss.

[0025] Figure 2This is a schematic diagram detailing an extreme ultraviolet (EUV) lithography tool according to an embodiment of the present disclosure, illustrating the exposure of a photoresist-coated substrate 210 with a patterned EUV beam. The exposure apparatus 200 is an integrated circuit lithography tool, such as a stepper, scanner, step-scanning system, direct-write system, or device employing contact and / or proximity masks, etc., and is provided with one or more optical elements 205a, 205b for irradiating a patterned optical element 205c (such as a mask) with an EUV beam to generate a patterned beam, and one or more reduction projection optical elements 205d, 205e for projecting the patterned beam onto the substrate 210. Mechanical assemblies (not shown) may be provided for generating controlled relative movement between the substrate 210 and the patterned optical element 205c. Figure 2 As further shown, the EUV lithography tool includes an EUV light source 100, in which plasma in the ZE state within the chamber 105 emits EUV light, which is collected by a collecting mirror 110 and reflected along the optical path to an exposure device 200 for irradiating the substrate 210.

[0026] As used herein, the term "optical device" is intended to be interpreted broadly as including, but not limited to, one or more components that reflect and / or transmit and / or manipulate incident light, and includes, but is not limited to: one or more lenses, windows, filters, wedges, prisms, gratings, optical fibers, etalons, diffusers, homogenizers, detectors, and other instrument components, apertures, axial prisms and mirrors including multilayer mirrors, near-normal incident mirrors, grazing incident mirrors, specular reflectors, diffusers, and combinations thereof. Furthermore, unless otherwise stated, the term "optical device" as used herein is not limited to components that operate within one or more specific wavelength ranges (e.g., EUV output light wavelengths, irradiating laser wavelengths, wavelengths suitable for metrological detection, or any other specific wavelength).

[0027] In this disclosure, the terms "mask," "photomask," and "mask plate" are used interchangeably. In this embodiment, the mask is a reflective mask. An exemplary structure of the mask includes a substrate having a suitable material, such as a low thermal expansion material or fused silica. In various examples, the material includes SiO2 doped with TiO2, or other suitable materials having low thermal expansion. The mask includes multiple reflective layers deposited on the substrate. The multiple layers include multiple film pairs, such as molybdenum-silicon (Mo / Si) film pairs (e.g., in each film pair, a molybdenum layer is above or below a silicon layer). Alternatively, the multiple layers may include molybdenum-beryllium (Mo / Be) film pairs, or other suitable materials that can be configured to highly reflect EUV light. The mask may also include a capping layer (e.g., ruthenium (Ru)) disposed on the multiple reflective layers for protection. The mask also includes an absorption layer (e.g., a chromium nitride (CrN) or tantalum boron nitride (TaBN) layer) deposited on the multiple layers. The absorption layer is patterned to define an integrated circuit (IC) layer. Alternatively, another reflective layer can be deposited on top of multiple layers and patterned to define an integrated circuit layer, thereby forming an EUV phase-shift mask.

[0028] In this embodiment, the semiconductor substrate is a semiconductor wafer to be patterned, such as a silicon wafer or other type of wafer. In this disclosure, the semiconductor substrate is coated with a resist layer sensitive to EUV light. Various components (including those described above) are integrated together and operable to perform a photolithography exposure process. The photolithography system may also include other modules or be integrated (or coupled) with other modules.

[0029] like Figure 1 As shown, the EUV radiation source 100 includes a target droplet generator 115 and an LPP collector 110 surrounded by a chamber 105. The target droplet generator 115 generates a plurality of target droplets DP. In some embodiments, the target droplets DP are tin (Sn) droplets. In some embodiments, each tin droplet has a diameter of about 30 micrometers (µm). In some embodiments, the tin droplets DP are generated at a rate of about 50-50,000 droplets per second and introduced into the excitation region ZE at a speed of about 70 meters per second (m / s). Other materials may also be used for the target droplets, such as tin-containing liquid materials, such as tin- or lithium (Li) eutectic alloys.

[0030] The excitation laser LR2 generated by the excitation laser source device 300 is a pulsed laser. In some embodiments, the excitation laser includes a preheating laser and a main laser. The preheating laser pulse is used to heat (or preheat) the target droplet to generate a pancake-shaped, low-density target, which is subsequently heated (or reheated) by the main laser pulse to generate emission-enhanced EUV light. In various embodiments, the preheating laser pulse has a spot size of about 100 µm or less, and the main laser pulse has a spot size of about 200-300 µm.

[0031] The laser pulse LR2 is generated by the excitation laser source 300. The laser source 300 may include a laser generator 310, a laser guiding optics 320, and a focusing device 330. In some embodiments, the laser source 310 includes a carbon dioxide (CO2) or neodymium-doped yttrium aluminum garnet (Nd:YAG) laser source. The laser LR1 generated by the laser generator 300 is guided by the laser guiding optics 320 and focused by the focusing device 330 into the excitation laser LR2, which is then introduced into the EUV radiation source 100.

[0032] The laser LR2 is directed into the excitation region ZE through a window (or lens). The window is made of a suitable material that is substantially transparent to the laser beam. The generation of the pulsed laser is synchronized with the generation of the target droplet. As the target droplet moves through the excitation region, it is pre-pulsed and heated, transforming it into a pancake-shaped, low-density target. The delay between the pre-pulse and the main pulse is controlled to allow the pancake-shaped target to form and expand to an optimal size and geometry. When the main pulse heats the pancake-shaped target, a high-temperature plasma is generated. This plasma emits EUV radiation, which is collected by a collecting mirror 110. The collector 110 has a reflective surface that reflects and focuses the EUV radiation for use in photolithography exposure processes. In some embodiments, a droplet trap 116 is mounted opposite the target droplet generator 115. The droplet trap 116 is used to trap excess target droplets. For example, some target droplets may be intentionally missed by the laser pulse.

[0033] Collector 110 includes a suitable coating material and shape for use as an EUV collecting, reflecting, and focusing mirror. In some embodiments, collector 110 is designed to have an elliptical geometry. In some embodiments, the coating material of collector 110 is similar to a reflective multilayer of an EUV mask. In some examples, the coating material of collector 110 includes multiple layers (e.g., multiple Mo / Si film pairs) and may also include a capping layer (e.g., Ru) coated on the multiple layers to substantially reflect EUV light. In some embodiments, collector 110 also includes a grating structure designed to effectively scatter a laser beam directed onto collector 110. For example, in some embodiments, a silicon nitride layer is coated on collector 110 and patterned to have a grating pattern.

[0034] In this EUV radiation source device, plasma induced by the applied laser generates physical debris (e.g., ions, gases, and atoms of droplets) and the desired EUV radiation. It is necessary to prevent material from accumulating on the collector 110, and it is also necessary to prevent physical debris from leaving the chamber 105 and entering the exposure tool 200.

[0035] like Figure 1As shown, in some embodiments, buffer gas is supplied from a first buffer gas supplier 130 through an orifice in collector 110, through which pulsed laser light is delivered to the tin droplet. In some embodiments, the buffer gas is H2, He, Ar, N2, or another inert gas. In some embodiments, H2 is used as H radicals generated by the ionization of the buffer gas, which can be used for cleaning purposes. Buffer gas can also be supplied towards collector 110 and / or around the edge of collector 110 through one or more second buffer gas suppliers 135. Furthermore, chamber 105 includes one or more gas outlets 140 such that the buffer gas is discharged outside chamber 105. Hydrogen has low absorption to EUV radiation. Hydrogen reaching the coated surface of collector 110 reacts chemically with the metal of the droplet to form hydrides, such as metal hydrides. When tin (Sn) is used as the droplet, stanane (SnH4) is formed, which is a gaseous byproduct of the EUV generation process. The gaseous SnH4 is then pumped out through outlet 140. However, it is difficult to expel all gaseous SnH4 from the chamber and prevent SnH4 from entering the exposure tool 200. In order to capture SnH4 or other debris, one or more debris collection mechanisms or devices 150 are employed in the chamber 105.

[0036] Figure 3A and Figure 3B An EUV reflective photomask blank according to an embodiment of the present disclosure is shown. Figure 3A It's a floor plan (viewed from the top). Figure 3B It is a cross-sectional view along the X direction.

[0037] In some embodiments, the EUV photomask with circuit patterns is formed from an EUV photomask blank 5. The EUV photomask blank 5 includes a substrate 10, a multilayer Mo / Si stack 15 of alternating layers of silicon and molybdenum, a capping layer 20, an absorption layer 25, and a first hard mask layer 30. Furthermore, a back conductive layer 45 is formed on the back side of the substrate 10, such as... Figure 3B As shown.

[0038] In some embodiments, the substrate 10 is formed of a low thermal expansion material. In some embodiments, the substrate is a low thermal expansion glass or quartz, such as fused silica or fused silica. In some embodiments, the low thermal expansion glass substrate transmits light having wavelengths including: visible wavelengths, a portion of the infrared wavelengths near the visible spectrum (near-infrared), and a portion of the ultraviolet wavelengths. In some embodiments, the low thermal expansion glass substrate absorbs extreme ultraviolet wavelengths and deep ultraviolet wavelengths near the extreme ultraviolet. In some embodiments, the substrate 10 has dimensions of 152 mm × 152 mm and a thickness of approximately 20 mm. In other embodiments, the substrate 10 has dimensions less than 152 mm × 152 mm and greater than or equal to 148 mm × 148 mm. The substrate 10 is square or rectangular in shape.

[0039] In some embodiments, the functional layer above the substrate (e.g., a multilayer Mo / Si stack 15, a capping layer 20, an absorber layer 25, and a first hard mask layer 30) has a smaller width than the substrate 10. In some embodiments, the size of the functional layer is in the range of about 138 mm × 138 mm to about 142 mm × 142 mm. In some embodiments, the shape of the functional layer is a square or a rectangle as shown in the plan view.

[0040] In other embodiments, the absorber layer 25 and the first hard mask layer 30 have smaller dimensions than the substrate 10, the multilayer Mo / Si stack 15, and the cap layer 20, ranging from approximately 138 mm × 138 mm to approximately 142 mm × 142 mm, such as... Figure 3C As shown. When the individual layers are formed, for example by sputtering, a smaller size for one or more functional layers can be formed by using a frame-shaped cap having an opening ranging from about 138 mm × 138 mm to about 142 mm × 142 mm. In other embodiments, all layers above substrate 10 have the same dimensions as substrate 10.

[0041] In some embodiments, the Mo / Si multilayer stack 15 comprises alternating layers of about 30 to about 60 layers each of silicon and molybdenum. In some embodiments, alternating layers of about 40 to about 50 layers each of silicon and molybdenum are formed. In some embodiments, the multilayer stack comprises 40 ± 1 pairs of molybdenum and silicon layers. In some embodiments, the reflectivity is greater than about 70% for a wavelength of interest (e.g., 13.5 nm). In some embodiments, the silicon and molybdenum layers are formed by chemical vapor deposition (CVD), plasma-enhanced CVD (PECVD), atomic layer deposition (ALD), physical vapor deposition (PVD) (including sputtering), or any other suitable film formation method. Each silicon and molybdenum layer is about 2 nm to about 10 nm thick. In some embodiments, the silicon and molybdenum layers have approximately the same thickness. In other embodiments, the silicon and molybdenum layers have different thicknesses. In some embodiments, each silicon layer is about 4 nm thick, and each molybdenum layer is about 3 nm thick.

[0042] In other embodiments, the multilayer stack 15 comprises alternating layers of molybdenum and beryllium. In some embodiments, the number of layers in the multilayer stack 15 ranges from about 20 to about 100 layers; however, any number of layers is permissible as long as sufficient reflectivity is maintained for imaging the target substrate. In some embodiments, the reflectivity is greater than about 70% for the wavelength of interest (e.g., 13.5 nm). In some embodiments, the multilayer stack 15 comprises about 30 to about 60 alternating layers of Mo and Be. In other embodiments of this disclosure, the multilayer stack 15 comprises about 40 to about 50 alternating layers of Mo and Be.

[0043] In some embodiments, a capping layer 20 is disposed on top of a Mo / Si multilayer 15 to prevent oxidation of the multilayer stack 15. In some embodiments, the capping layer 20 is made of ruthenium, a ruthenium alloy (e.g., RuNb, RuZr, RuZrN, RuRh, RuNbN, RuRhN, RuV, or RuVN), or a ruthenium-based oxide (e.g., RuO2, RuNbO, RuVO, or RuON) with a thickness of about 2 nm to about 10 nm. In some embodiments, the thickness of the capping layer 20 is in the range of about 2 nm to about 5 nm. In some embodiments, the capping layer 20 has a thickness of 3.5 nm ± 10%. In some embodiments, the capping layer 20 is formed by CVD, PECVD, ALD, PVD (e.g., sputtering), or any other suitable film-forming method. In other embodiments, a Si layer is used as the capping layer 20.

[0044] In some embodiments, such as Figure 3D As shown, a protective (intermediate) layer 22 is formed between the cap layer 20 and the absorber layer 25. Similarly, in some embodiments, an oxide layer 27 is formed on the top surface of the absorber layer 25, such as... Figure 3D As shown. In some embodiments, the hard mask layer further includes a second hard mask layer 32, which is formed on top of the first hard mask layer 30, as shown. Figure 3D As shown. In some embodiments, the first hard mask layer 30 and the second hard mask layer 32 are made of different materials. In some embodiments, the mask preform 5 includes a protective layer 22, an oxide layer 27, and a second hard mask layer 32. In other embodiments, the mask preform includes only two of any combination of the protective layer 22, the oxide layer 27, and the second hard mask layer 32. In some embodiments, the mask preform includes only one of the protective layer 22, the oxide layer 27, and the second hard mask layer 32.

[0045] In some embodiments, the protective layer 22 protects the cap layer 20. In some embodiments, the protective layer 22 comprises a Ta-based material, such as TaB, TaO, TaO, or TaBN; silicon; a silicon-based compound (such as silicon oxide, silicon nitride, SiON, or MoSi); ruthenium; or a ruthenium-based compound (Ru or RuB). In some embodiments, the protective layer 22 has a thickness of about 2 nm to about 20 nm. In some embodiments, the protective layer 22 is formed by CVD, PECVD, ALD, PVD, or any other suitable film-forming method. In some embodiments, the protective layer 22 serves as an etch stop layer during the patterning operation of the absorber layer.

[0046] In other embodiments, the intermediate layer 22 is a photocatalytic layer that can catalyze hydrocarbon residues formed on the photomask into CO2 and / or H2O using EUV radiation. This performs in-situ self-cleaning of the mask surface. In some embodiments, oxygen and hydrogen are injected into the EUV chamber in the EUV scanner system to maintain chamber pressure (e.g., about 2 Pa). The chamber background gas can be a source of oxygen. In addition to its photocatalytic function, the photocatalytic layer is designed to have sufficient durability and resistance to a variety of chemicals and chemical processes (e.g., cleaning and etching). Ozoned water can be used in mask manufacturing processes to fabricate EUV reflective masks. Ozoned water can damage the cap layer 20 made of Ru, which can lead to a significant decrease in EUV reflectivity. Furthermore, after Ru oxidation, Ru oxide is easily etched away by etchants (e.g., Cl2 or CF4 gas). In some embodiments, the photocatalytic layer comprises one or more of titanium dioxide (TiO2), tin oxide (SnO), zinc oxide (ZnO), and cadmium sulfide (CdS). The thickness of the photocatalytic layer 22 is in the range of about 2 nm to about 10 nm in some embodiments, and in the range of about 3 nm to about 7 nm in other embodiments. When the thickness is too thin, the photocatalytic layer may be insufficient to serve as an etch stop layer. When the thickness is too large, the photocatalytic layer may absorb EUV radiation.

[0047] In some embodiments, the intermediate layer 22 is an antireflective layer. In some embodiments, the antireflective layer 22 is made of silicon oxide and has a thickness of about 2 nm to about 10 nm. In other embodiments, a TaBO layer having a thickness in the range of about 12 nm to about 18 nm is used as the antireflective layer 22. In some embodiments, the thickness of the antireflective layer 22 is in the range of about 3 nm to about 6 nm. In some embodiments, the antireflective layer 22 is formed by CVD, PECVD, ALD, PVD, or any other suitable film-forming method.

[0048] In some embodiments, the absorber layer 25 is disposed above the intermediate (protective) layer 22; in other embodiments, without the intermediate protective layer, the absorber layer is disposed above the cap layer 20. In some embodiments, the absorber layer 25 comprises a Cr-based material, such as Cr, CrN, CrON, and / or CrCON. In some embodiments, in the case of CrON or CrCON, the nitrogen content is in the range of about 10 atomic% to about 30 atomic%. In some embodiments, the absorber layer 25 has a multilayer structure of Cr, CrN, CrON, and / or CrCON.

[0049] In some embodiments, a CrN layer is used as absorber layer 25. In some embodiments, when a CrN layer is used, the nitrogen content is in the range of about 16 atomic% to about 40 atomic%. In some embodiments, when the nitrogen content is in the range of about 16 atomic% to about 30 atomic%, the CrN absorber layer comprises a Cr phase and a Cr2N phase. In some embodiments, when the nitrogen content is in the range of about 30 atomic% to about 33 atomic%, the CrN absorber layer is essentially made of the Cr2N phase (e.g., greater than 95 vol%). In some embodiments, when the nitrogen content is in the range of about 33 atomic% to about 40 atomic%, the CrN absorber layer comprises a Cr2N phase and a CrN phase. These phases can be observed by electron energy loss spectroscopy (EELS), transmission electron microscopy (TEM), and / or X-ray diffraction (XRD) analysis. In some embodiments, the two phases form a solid solution.

[0050] In some embodiments, the nitrogen concentration in the absorber layer 25 is non-uniform. In some embodiments, the nitrogen concentration in the middle or center of the absorber layer 25 is higher than that in the surface region of the absorber layer 25. In some embodiments, the CrN absorber layer includes one or more impurities other than Cr and N, the content of which is less than about 5 atomic%. In some embodiments, the absorber layer 25 also includes one or more elements selected from Co, Te, Hf and / or Ni.

[0051] The thickness of the absorber layer 25 is in the range of about 20 nm to about 50 nm in some embodiments, and in the range of about 35 nm to about 46 nm in other embodiments.

[0052] In some embodiments, the oxide layer 27 comprises one or more of Cr2O3 or CrO2. In some embodiments, the oxide layer 27 is formed during the fabrication operation of the mask preform. In some embodiments, the thickness of the oxide layer 27 is in the range of about 1 nm to about 3 nm.

[0053] In some embodiments, a first hard mask layer 30 is disposed on oxide layer 27. In some embodiments, the first hard mask layer 30 is formed on absorber layer 25. In some embodiments, the first hard mask layer 30 is made of a Ta-based material, such as TaB, TaO, TaBO, or TaBN. In other embodiments, the first hard mask layer 30 is made of silicon, a silicon-based compound (e.g., silicon oxide, silicon nitride, SiON, or MoSi), ruthenium, or a ruthenium-based compound (Ru or RuB). In some embodiments, the first hard mask layer 30 is made of the same or similar material as protective layer 22. In some embodiments, the first hard mask layer 30 has a thickness of about 2 nm to about 20 nm. In some embodiments, the first hard mask layer 30 is formed by CVD, PECVD, ALD, PVD, or any other suitable film-forming method.

[0054] In some embodiments, a second hard mask layer 32 is disposed above a first hard mask layer 30. In some embodiments, the second hard mask layer 32 is made of one or more of GaN, CrON, CrCON, silicon oxide, SiCO, and / or yttrium oxide. In some embodiments, the second hard mask layer 32 has a thickness of about 2 nm to about 20 nm. In some embodiments, the thickness of the second hard mask layer 32 is less than or greater than the thickness of the first hard mask layer 30. In some embodiments, the second hard mask layer 32 is formed by CVD, PECVD, ALD, PVD, or any other suitable film deposition method.

[0055] In some embodiments, for plasmas including chlorine and oxygen, the second hard mask layer 32 is made of a material with an etch rate higher than that of the first hard mask layer 30. In some embodiments, for plasmas including fluorine, the first hard mask layer 30 is made of a material with an etch rate higher than that of the second hard mask layer 32.

[0056] In some embodiments, one or more functional layers above the substrate (e.g., a multilayer Mo / Si stack 15, a capping layer 20, a protective layer 22, an absorption layer 25, an oxide layer 27, a first hard mask layer 30, and a second hard mask layer 32) have a polycrystalline structure (e.g., a nanocrystalline structure) or an amorphous structure.

[0057] In some embodiments, a back conductive layer 45 is disposed on a second main surface of the substrate 10, which is opposite to a first main surface of the substrate 10 on which a Mo / Si multilayer stack 15 is formed. In some embodiments, the back conductive layer 45 is formed of TaB (tantalum boride) or other Ta-based conductive materials. In some embodiments, tantalum boride is crystalline. Crystalline tantalum boride includes at least one of TaB, Ta5B6, Ta3B4, and TaB2. In other embodiments, tantalum boride is polycrystalline or amorphous. In other embodiments, the back conductive layer 45 is made of a Cr-based conductive material (CrN or CrON). In some embodiments, the sheet resistance of the back conductive layer 45 is equal to or less than 20 Ω / □. In some embodiments, the sheet resistance of the back conductive layer 45 is equal to or greater than 0.1 Ω / □. In some embodiments, the surface roughness Ra of the back conductive layer 45 is equal to or less than 0.25 nm. In some embodiments, the surface roughness Ra of the back conductive layer 45 is equal to or greater than 0.05 nm. Furthermore, in some embodiments, the flatness of the back conductive layer 45 is equal to or less than 50 nm (within an EUV photomask). In some embodiments, the flatness of the back conductive layer 45 is greater than 1 nm. In some embodiments, the thickness of the back conductive layer 45 is in the range of about 50 nm to about 400 nm. In other embodiments, the back conductive layer 45 has a thickness of about 50 nm to about 100 nm. In some embodiments, the thickness is in the range of about 65 nm to about 75 nm. In some embodiments, the back conductive layer 45 is formed by atmospheric pressure CVD, low pressure CVD, PECVD, laser-enhanced CVD, ALD, molecular beam epitaxy (MBE), PVD (including thermal deposition, pulsed laser deposition, electron beam evaporation, ion beam assisted evaporation, and sputtering), or any other suitable film-forming method. In some embodiments, in the case of CVD, the source gas includes TaCl5 and BCl3.

[0058] In some embodiments, such as Figure 3EAs shown, a substrate protective layer 12 is formed between the substrate 10 and the multilayer stack 15. In some embodiments, the substrate protective layer 12 is formed of Ru or a Ru compound (e.g., RuO, RuNb, RuNbO, RuZr, and RuZrO). In some embodiments, the substrate protective layer 12 is formed of the same or a different material as the cap layer 20. In some embodiments, the thickness of the substrate protective layer 12 is in the range of about 2 nm to about 10 nm. In some embodiments, the mask preform 5 includes the substrate protective layer 12, the second hard mask layer 32, the oxide layer 27, and the protective layer 22. In other embodiments, the mask preform 5 includes only one of the substrate protective layer 12, the second hard mask layer 32, the oxide layer 27, and the protective layer 22. In other embodiments, the mask preform 5 includes any combination of the substrate protective layer 12, the second hard mask layer 32, the oxide layer 27, and the protective layer 22.

[0059] Figures 4 to 11 A method for fabricating an EUV photomask for EUV lithography is illustrated schematically. It should be understood that it is possible to... Figures 4 to 11 Additional operations are provided before, during, and after the process shown. In other embodiments of the method, some of the operations described below may be replaced or eliminated. The order of operations / processes may be interchanged.

[0060] In some embodiments, during the fabrication of an EUV photomask, a first photoresist layer 35 is formed on the first hard mask layer 30 of the EUV photomask blank 5, such as... Figure 4 As shown. In some embodiments, the EUV photomask preform is inspected before the formation of the first photoresist layer 35.

[0061] In some embodiments, the photoresist layer 35 is patterned to form at least one opening 41 exposing the hard mask layer 30. The photoresist layer 35 is patterned by selectively exposing it to activation radiation 40, such as... Figure 5 As shown, the selectively exposed photoresist layer 35 is then developed to form at least one opening 41, as... Figure 6 As shown. In some embodiments, the activation radiation 40 is an electron beam or an ion beam. Figure 5 and Figure 6In the illustrated embodiments, the photoresist layer is made of a positive photoresist, wherein portions of the photoresist exposed to activation radiation are removed during development. In other embodiments, the photoresist is a negative photoresist, wherein portions of the photoresist layer not exposed to activation radiation are removed during development. In some embodiments, the opening 41 corresponds to a pattern of semiconductor device features that will be used to form in subsequent operations using an EUV photomask. In some embodiments, the thickness of the first photoresist layer 35 disposed on the second hard mask layer 32 is in the range of about 500 nm to about 1000 nm.

[0062] Next, as Figure 7 As shown, a pattern 40 in the first photoresist layer 35 is extended into the first hard mask layer 30 and the absorber layer 25, thereby forming a trench 50 in the absorber layer that exposes the cap layer 20. In some embodiments, an opening 41 extending into the first hard mask layer 30 is formed by etching with a suitable wet or dry etchant selectively targeting the first hard mask layer 30. In some embodiments, the first hard mask layer 30 and the absorber layer 25 are patterned using a plasma dry etching operation with chlorine-containing gases (e.g., Cl2, HCl, BCl, and CCl4) and oxygen-containing gases (e.g., O2). In other embodiments, the plasma dry etching operation uses fluorine-containing gases (e.g., fluorocarbons (CF4, CHF3, etc.) and SF6) to pattern the first hard mask layer 30. In some embodiments, different etchants are used to etch the first hard mask layer 30 and the absorber layer 25.

[0063] After forming trenches 50 in the absorption layer, the first photoresist layer 35 is removed using a photoresist stripper to expose the upper surface of the first hard mask layer 30, such as... Figure 8 As shown. In some embodiments, the photoresist layer 35 is removed after the opening is etched in the first hard mask layer 30 and before the opening is extended through the absorber layer 25.

[0064] In some embodiments, trench 50 has a width W1 ranging from about 300 nm to about 1 µm. In some embodiments, after the trench is etched, there is no measurable oxide layer on the sidewalls of the trench. In other words, trench 50 has a sidewall oxide layer with a thickness T1 of about 0 nm.

[0065] In some embodiments, the hard mask layer includes a first hard mask layer 30 and a second hard mask layer 32 disposed on the first hard mask layer 30, such as Figure 3D and Figure 3EAs shown. In some embodiments, the material of the first hard mask layer 30 is selected to have high etch resistance (low etch rate) to plasma dry etching operations using chlorine and oxygen, and etching essentially stops at the first hard mask layer 30 after the opening 41 is extended into the second hard mask layer 32. A pattern including at least one opening in the second hard mask layer 32 is then extended into the first hard mask layer 30. In some embodiments, different etchants (such as fluorinated gases, e.g., fluorocarbons (CF4, CHF3, etc.) and SF6) are used to extend the pattern 41 into the first hard mask layer 30.

[0066] In embodiments that include an oxide layer 27 disposed above the absorber layer 25, the oxide layer 27 is subsequently etched to expose the absorber layer 25. In some embodiments, the material of the oxide layer 27 is selected to have high etch resistance (low etch rate) to plasma dry etching operations using fluorine, and the etching of the first hard mask layer 30 substantially stops at the oxide layer 27.

[0067] Then, the patterns in the first hard mask layer 30 and the second hard mask layer 32 are extended into the absorber layer 25 to form a trench 50 that exposes a portion of the cap layer 20 or the intermediate layer 22 (in embodiments including the intermediate layer).

[0068] The absorber layer 25 and oxide layer 27 (if present) are etched using a suitable wet or dry etchant that is selective for the first hard mask layer 30 and the intermediate layer 22 (if present). In some embodiments, the material of the intermediate layer 22 is selected to have high etch resistance (lower etch rate) to the plasma dry etching operation of the absorber layer, and the etching essentially stops at the intermediate layer 22. In some embodiments, the second hard mask layer 32 (if present) is removed during the etching of the oxide layer 27 and / or the absorber layer 25. Specifically, when the second hard mask layer 32 is made of a Cr-based material (e.g., CrN, CrON, or CrCON), the second hard mask layer 32 is removed during the etching of the oxide layer 27 and / or the absorber layer 25. If the second hard mask layer 32 remains after etching the absorber layer 25, in some embodiments, an additional removal operation of the second hard mask layer 32 is performed using a suitable wet or dry etching process.

[0069] Then, the first hard mask layer 30 is removed using a suitable etching technique to form the photomask 75. In some embodiments, the etching is wet etching and / or dry etching. In some embodiments, exposed portions of the intermediate layer 22, if present, are also removed. In some embodiments, after removing the first hard mask layer, the photomask 75 undergoes a first plasma treatment including a first plasma 65, such as... Figure 9AAs shown. In some embodiments, the first plasma 65 is formed from a mixture of oxygen and water vapor. In some embodiments, the first plasma treatment is an inductively coupled plasma treatment. Oxygen plasma removes organic contaminants from the surface of photomask 75. In oxygen / water vapor plasma cleaning, water vapor can be used as a process gas along with oxygen to enhance the cleaning process. Water vapor can be used to decompose organic contaminants, improve the removal of certain materials, and / or introduce a higher level of hydrophilicity to the surface.

[0070] Before ignition of the plasma, an oxygen and water vapor stream can initially be applied using a source power of about 0 W and a bias power of about 0 W. In some embodiments, the gas stream includes an inert carrier gas. In some embodiments, the carrier gas is one or more selected from helium, neon, argon, xenon, and nitrogen. In some embodiments, the oxygen / water vapor plasma is applied for about 10 s to about 180 s with a source power of about 500 to about 1500 W and a bias power of about 0 W. In some embodiments, the gas flow rate of the source gas of the plasma is in the range of about 0.05 L / min to about 1 L / min, and in other embodiments in the range of about 0.1 L / min to about 0.5 L / min. Parameters for the first plasma treatment below the disclosed range may result in insufficient removal of organic contaminants, and parameters for the first plasma treatment above the disclosed range may not significantly improve the removal of organic contaminants.

[0071] However, the oxygen / water vapor plasma 65 also forms a thin oxide layer 60 on the surface of the absorber layer 25 and the exposed portions of the cap layer 20. In some embodiments, the thin oxide layer 60 has a thickness T2 ranging from about 1 nm to about 5 nm. In other embodiments, the thin oxide layer 60 has a thickness T2 ranging from about 2.5 nm to about 3.5 nm. In some embodiments, the formation of the thin oxide layer 60 reduces the trench width W2 by about 2 nm to about 10 nm, and in other embodiments by about 5 nm to about 7 nm. In some embodiments, after the first hard mask removal, the trench width W2 is about 290 nm to about 998 nm in some embodiments, and about 295 nm to about 990 nm in other embodiments. The thin oxide layer 60 protects the absorber layer 25 and the cap layer during subsequent wet cleaning operations. If the thickness T2 of the thin oxide layer 60 is less than the disclosed range, insufficient protection may be provided for the absorber layer pattern and the cap layer. If the thickness T2 of the thin oxide layer 60 is greater than the disclosed range, control over fine pattern details and pattern resolution may be lost.

[0072] After the first plasma treatment, the processing chamber for removing the first hard mask layer is purged with a mixture of hydrogen and inert gases (e.g., helium, neon, argon, nitrogen, and combinations thereof) for approximately 10 to approximately 60 seconds. Following purging of the processing chamber, as... Figure 9B As shown, a second plasma treatment is performed on photomask 75 using plasma 80 formed from a mixture of hydrogen and an inert gas. In some embodiments, plasma 80 is an inductively coupled plasma. In some embodiments, the concentration of hydrogen in the inert gas is in the range of about 0.5 mol.% to about 10 mol.%, and in other embodiments it is in the range of about 1 mol.% to about 5 mol.%. The inert gas may be selected from helium, neon, argon, nitrogen, and combinations thereof. In some embodiments, the inert gas is helium. In some embodiments, the first plasma treatment and the second plasma treatment are performed in the same processing chamber. In other embodiments, the first plasma treatment and the second plasma treatment are performed in different processing chambers. Hydrogen concentrations below the disclosed range may result in insufficient protection of the oxide layer, and hydrogen concentrations above the disclosed range may not significantly improve the protection of the oxide layer.

[0073] In some embodiments, the inductively coupled plasma parameters during plasma processing of photomask 75 include a source power in the range of about 500 W to about 4000 W without bias power applied (bias power is about 0 W), and in other embodiments, a source power in the range of about 1000 W to about 3000 W without bias power applied. In some embodiments, the gas flow rate of the source gas of the plasma is in the range of about 0.1 L / min to about 3.5 L / min, and in other embodiments, it is in the range of about 0.25 L / min to about 2.5 L / min. In some embodiments, the pressure in the processing chamber during inductively coupled plasma processing is in the range of about 300 mTorr to about 3000 mTorr, and in other embodiments, it is in the range of about 600 mTorr to about 1500 mTorr. In some embodiments, the thin oxide layer 60 is exposed to inductively coupled plasma processing (or a second plasma etching) for about 15 s to about 600 s, and in other embodiments, for about 30 s to about 300 s. In some embodiments, inductively coupled plasma treatment is performed at a temperature ranging from about 20°C to about 30°C in some embodiments and from about 24°C to about 26°C in other embodiments. Parameters for the second plasma treatment below the disclosed range may result in insufficient protection of the oxide layer, and parameters for the second plasma treatment above the disclosed range may result in no significant improvement in the protection of the oxide layer.

[0074] In some embodiments, the second plasma etching converts water- and / or acid-soluble oxides on the surfaces of the absorber layer and the cap layer into water- and / or acid-insoluble oxides. For example, in some embodiments, the second plasma etching converts water-soluble chromium oxide with various chromium / oxygen ratios into insoluble chromium oxide in the presence of hydrogen radicals, as follows: H Cr m O n (aq) → Cr2O3(s) + CrO2(s). In some embodiments, the second plasma etching converts water-soluble ruthenium oxide with various ruthenium / oxygen ratios into insoluble ruthenium oxide in the presence of hydrogen radicals, as follows: H RuO x (aq) → RuO2 (s) + RuO(s).

[0075] In some embodiments, the first stage of the cleaning process includes: after removing the first hard mask layer 30, applying a reducing agent 90 to the photomask 75, such as... Figure 10 As shown. In some embodiments, the reducing agent includes hydrogen plasma, hydrogen, carbon monoxide, sodium borohydride, lithium aluminum hydride, hydrazine, hydrogen peroxide, sulfur dioxide, sodium dithionite, and / or ascorbic acid. The hydrogen plasma may include hydrogen radicals formed by ICP, as disclosed herein. In some embodiments, the hydrogen plasma is formed from a mixture of hydrogen and an inert gas. In some embodiments, hydrogen is applied as a mixture of hydrogen and an inert gas. In some embodiments, the concentration of hydrogen in the inert gas is in the range of about 0.5 mol.% to about 10 mol.%, and in other embodiments in the range of about 1 mol.% to about 5 mol.%. The inert gas may be selected from helium, neon, argon, nitrogen, and combinations thereof. In some embodiments, the inert gas is helium. In some embodiments, the reducing agent is applied as a gas or a liquid. In some embodiments, the reducing agent is dissolved in a solvent. Suitable solvents may include water; alcohols, including methanol, n-propanol, isopropanol, n-butanol, sec-butanol or tert-butanol, pentanol and hexanol; ethers, including dimethyl ether, diethyl ether, dipropyl ether, dibutyl ether, dimethoxyethane, bis(2-methoxyethyl) ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether and dioxane; tetrahydrofuran; or acetonitrile.

[0076] In some embodiments, the reducing agent treatment converts water- and / or acid-soluble oxides on the surfaces of the absorber layer and the cap layer into water- and / or acid-insoluble oxides, as explained above regarding the second plasma etching.

[0077] Subsequently Figure 9B or Figure 10A wet cleaning operation is performed on the photomask 75. In some embodiments, the wet cleaning operation includes applying an aqueous solution of sulfuric acid and hydrogen peroxide to the photomask 75. In some embodiments, the cleaning solution is a piranha solution. Piranha solution can be used to remove organic contaminants from the photomask. In other embodiments, the wet cleaning solution comprises a mixture of carbon dioxide or hydrogen dissolved in water or deionized water.

[0078] For example, in some embodiments, the application of a reducing agent and subsequent wet cleaning effectively remove tin contaminants, as shown in the following reaction: a first reaction caused by the reducing agent removes the passivation layer to expose elemental tin, as follows: H SnO + SnO2→ Sn Then, the elemental tin is oxidized and dissolved by a sulfuric acid / peroxide wet wash, as shown below: OH Sn→ Sn 2+ .

[0079] In some embodiments, the application of a reducing agent and subsequent wet cleaning operations provide removal of: organic contaminants; metallic contaminants, including Cr, Ta, Al, Fe, Na, Mg, and Ru; and non-metallic contaminants, including Si and S. In some embodiments, after performing the reducing agent treatment and subsequent wet cleaning operations, there is a shift in the critical size of less than 0.1 nm.

[0080] In some embodiments, defects are detected using a laser scanning tool that combines optics and image processing methods to examine photomask defects, such as pattern anomalies or particles. In some embodiments, the type of defect is determined by energy-dispersive X-ray (EDX) analysis to determine the elemental composition of the material. In some embodiments, critical dimension (CD) measurements are performed using a CD scanning electron microscope metrology tool that measures the lines and / or spaces of the patterned mask.

[0081] like Figure 11As shown, after the wet cleaning operation, the thin oxide layer 60 remains substantially intact. The insoluble oxide formed during the second plasma etching operation (or plasma treatment) protects the thin oxide layer 60 from degradation by the wet cleaning operation because the thin oxide layer is substantially insoluble in aqueous and acidic cleaning solutions (e.g., piranha solution). In some embodiments, after the wet cleaning operation, the thickness of the thin oxide layer T3 is in the range of about 0.5 nm to about 5 nm in some embodiments. In other embodiments, the thin oxide layer 60 has a thickness T3 in the range of about 2 nm to about 3.5 nm. In some embodiments, the ratio of the thickness T3 of the oxide layer after the wet cleaning operation to the thickness T2 of the oxide layer before the wet cleaning operation is in the range of 0.8 to 1.0. In some embodiments, after the wet cleaning operation, the trench width W3 is in the range of about 291 nm to about 995 nm in some embodiments, and in the range of about 295 nm to about 990 nm in other embodiments. If the thickness T3 of the thin oxide layer 60 is less than the disclosed range, there may be insufficient protection for the absorber pattern and the capping layer. If the thickness T3 of the thin oxide layer 60 is greater than the disclosed range, control over fine pattern details and pattern resolution may be lost.

[0082] Figures 12 to 23 Another embodiment of a method for fabricating an EUV photomask for EUV lithography is illustrated schematically. It should be understood that... Figures 12 to 23 Additional operations are provided before, during, and after the illustrated process, and some of the operations described below may be replaced or eliminated for additional embodiments of the disclosed method. The order of operations / processes may be interchanged.

[0083] like Figure 12 As shown, a first photoresist layer 35 is formed on the first hard mask layer 30 of the EUV photomask preform 5. In some embodiments, the photomask preform 5 and Figure 4 The photomask preform shown is identical. In other embodiments, the photomask preform includes one or more of a second hard mask layer 32, an oxide layer 27, an intermediate layer 22, and a substrate protection layer 12, as referenced herein. Figure 3D , Figure 3E as well as Figures 4 to 11 As disclosed in the written description of the embodiments. In some embodiments, the EUV photomask preform is inspected prior to the formation of the first photoresist layer 35.

[0084] In some embodiments, the first photoresist layer 35 is patterned to form a pattern that exposes the hard mask layer 30. The photoresist layer 35 is patterned by selectively exposing it to activation radiation 40, such as... Figure 13 As shown, the selectively exposed photoresist layer 35 is then developed to form pattern 42, as shown. Figure 14 As shown. In some embodiments, the activation radiation 40 is an electron beam or an ion beam. Figure 13 and Figure 14 In the illustrated embodiments, the photoresist layer is made of a positive photoresist, wherein portions of the photoresist exposed to activation radiation are removed during development. In other embodiments, the photoresist is a negative photoresist, wherein portions of the photoresist layer not exposed to activation radiation are removed during development. In some embodiments, pattern 42 includes features having narrower and wider spacing. In some embodiments, 42 corresponds to a pattern of a semiconductor device structure that will be used to form in subsequent operations using an EUV photomask. In some embodiments, the thickness of the first photoresist layer 35 disposed on the hard mask layer 32 is in the range of about 500 nm to about 1000 nm.

[0085] Next, the pattern 42 in the first photoresist layer 35 is extended into the hard mask layer 30 and the absorption layer 25, thereby forming a pattern 52 in the absorption layer that exposes the capping layer 20, such as... Figure 15 As shown. In some embodiments, a pattern 42 extending into the hard mask layer 30 is formed by etching with a suitable wet or dry etchant that is selective to the first hard mask layer 30. In some embodiments, the first hard mask layer 30 and the absorber layer 25 are patterned using a plasma dry etching operation with a chlorine-containing gas (e.g., Cl2, HCl, BCl, and CCl4) and an oxygen-containing gas (e.g., O2). In other embodiments, the plasma dry etching operation uses a fluorine-containing gas (e.g., fluorocarbons (CF4, CHF3, etc.) and SF6) to pattern the first hard mask layer 30. In some embodiments, different etchants are used to etch the first hard mask layer 30 and the absorber layer 25.

[0086] After the pattern 52 is formed in the absorption layer, the first photoresist layer 35 is removed by a photoresist stripper to expose the upper surface of the first hard mask layer 30, such as... Figure 16 As shown. In some embodiments, the photoresist layer 35 is removed after the opening is etched in the first hard mask layer 30 and before the opening is extended through the absorber layer 25.

[0087] In some embodiments, the absorber layer pattern 52 has a wide width W4 separating the pattern features, ranging from about 100 nm to about 300 nm, and a narrow width W5 separating other pattern features, ranging from about 30 nm to about 100 nm. In some embodiments, the narrow width W5 ranges from about 40 nm to about 80 nm. In some embodiments, after the pattern is formed by etching, there is no measurable oxide layer on the sidewalls of the trench. In other words, the pattern features have a sidewall oxide layer with thicknesses T4 and T5 of about 0 nm.

[0088] In some embodiments, the hard mask layer includes a first hard mask layer 30 and a second hard mask layer 32, as described herein. The material used for the two hard mask layers 30, 32 can be any material disclosed herein for the first hard mask layer 30 and the second hard mask layer 32. Additionally, the first hard mask layer 30 and the second hard mask layer 32 can be etched to extend the pattern 42 according to the etch operations disclosed herein for the first hard mask layer 30 and the second hard mask layer 32.

[0089] In embodiments including an oxide layer 27 over an absorber layer 25, the oxide layer 27 is subsequently etched to expose the absorber layer, as referenced herein. Figures 4 to 11 The embodiments disclosed herein. Then, the pattern 42 in the first hard mask layer 30 is extended into the absorber layer 25 to form a pattern 52, which exposes a portion of the cap layer 20 or the intermediate layer 22 (in embodiments including the intermediate layer).

[0090] Then, the first hard mask layer 30 is removed to form the photomask 85. In some embodiments, the etching is wet etching and / or dry etching. In some embodiments, exposed portions of the intermediate layer (if present) are also removed. In some embodiments, after removing the first hard mask layer, the photomask 85 undergoes a first plasma treatment including a first plasma 65, such as... Figure 17A As shown. In some embodiments, the first plasma 65 comprises a mixture of oxygen and water vapor. In some embodiments, the first plasma treatment is an inductively coupled plasma treatment. Oxygen plasma removes organic contaminants from the surface of photomask 85. In oxygen / water vapor plasma cleaning, water vapor can be used together with oxygen as a process gas to enhance the cleaning process. Water vapor can be used to decompose organic contaminants, improve the removal of certain materials, and / or introduce a higher level of hydrophilicity to the surface. Parameters of the oxygen / water vapor plasma treatment (first plasma treatment) are referenced herein. Figure 9A What has been made public.

[0091] Oxygen / water vapor plasma forms a thin oxide layer 60 on the surface of the absorber layer 25 and the exposed portion of the cap layer 20. In some embodiments, the thin oxide layer 60 has a thickness T6 on the sidewalls of the wide-spaced features and a thickness T7 on the sidewalls of the narrow-spaced features, ranging from about 1 nm to about 5 nm. In other embodiments, the thicknesses T6 and T7 of the thin oxide layer 60 range from about 2.5 nm to about 3.5 nm. In some embodiments, the thicknesses T6 and T7 of the thin oxide layer are substantially the same for both the wide-spaced and narrow-spaced features. In some embodiments, the formation of the thin oxide layer 60 reduces the width of the space between the patterned features by about 2 nm to about 10 nm, and in other embodiments by about 5 nm to about 7 nm. In some embodiments, after the first hard mask is removed, the width W6 between the wide-spaced features of the pattern 52 ranges from about 90 nm to about 298 nm in some embodiments, and from about 95 nm to about 290 nm in other embodiments. In some embodiments, after the first hard mask is removed, the width W7 between the narrowly spaced features of pattern 52 is in the range of about 20 nm to about 98 nm in some embodiments, and in the range of about 25 nm to about 90 nm in other embodiments. If the thicknesses T6 and T7 of the thin oxide layer 60 are less than the disclosed range, there may be insufficient protection for the absorption layer pattern and the capping layer. If the thicknesses T6 and T7 of the thin oxide layer 60 are greater than the disclosed range, control over fine pattern details and pattern resolution may be lost.

[0092] After the first plasma treatment, the processing chamber for removing the first hard mask layer is purged with a mixture of hydrogen and inert gases (e.g., helium, neon, argon, nitrogen, and combinations thereof) for approximately 10 to approximately 180 seconds. Following purging of the processing chamber, as... Figure 17B As shown, a second plasma treatment is performed on a photomask 85 using a plasma 80 formed from a mixture of hydrogen and an inert gas. In some embodiments, plasma 80 is an inductively coupled plasma. In some embodiments, the concentration of hydrogen in the inert gas is in the range of about 0.5 mol.% to about 10 mol.%, and in other embodiments it is in the range of about 1 mol.% to about 5 mol.%. The inert gas may be selected from helium, neon, argon, nitrogen, and combinations thereof. In some embodiments, the inert gas is helium. In some embodiments, the first plasma treatment and the second plasma treatment are performed in the same processing chamber. In other embodiments, the first plasma treatment and the second plasma treatment are performed in different processing chambers. Hydrogen concentrations below the disclosed range may result in insufficient protection of the oxide layer, and hydrogen concentrations above the disclosed range may not significantly improve the protection of the oxide layer. The parameters of the hydrogen / inert gas plasma treatment (second plasma treatment) are referenced herein. Figure 9BWhat has been made public.

[0093] In some embodiments, the first stage of the cleaning process includes applying a reducing agent 90 to the photomask 85 after removing the first hard mask layer 30, such as... Figure 18 As shown, and referenced in this article Figure 10 The subject of discussion.

[0094] As explained herein, in some embodiments, a reducing agent treatment or a second plasma treatment converts water- and / or acid-soluble oxides on the surfaces of the absorber and cap layers into water- and / or acid-insoluble oxides. Subsequently, [the text abruptly ends here]. Figure 17B and Figure 18 The photomask 85 shown is subjected to a wet cleaning operation, as referenced in this document. Figures 4 to 11 The embodiments disclosed herein.

[0095] like Figure 19 As shown, after the wet cleaning operation, the thin oxide layer 60 remains substantially intact. The insoluble oxide formed during the second plasma treatment protects the thin oxide layer 60 from degradation by the wet cleaning operation because the thin oxide layer is substantially insoluble in aqueous and acidic cleaning solutions (e.g., piranha solution). In some embodiments, after the wet cleaning operation, the thicknesses of the thin oxide layers T8 and T9 are in the range of about 0.5 nm to about 5 nm in some embodiments. In other embodiments, the thicknesses T8 and T9 of the thin oxide layer 60 are in the range of about 2 nm to about 3.5 nm. In some embodiments, the ratio of the thicknesses T8 and T9 of the oxide layer after the wet cleaning operation to the thicknesses T6 and T7 of the oxide layer before the wet cleaning operation is in the range of 0.8 to 1.0. In some embodiments, after the wet cleaning operation, the width W8 between the widely spaced features of pattern 52 is in the range of about 91 nm to about 298 nm in some embodiments, and in the range of about 95 nm to about 290 nm in other embodiments. In some embodiments, after a wet cleaning operation, the width W9 between the narrowly spaced features of pattern 52 is about 21 nm to about 98 nm in some embodiments, and about 25 nm to about 90 nm in others. If the thicknesses T8 and T9 of the thin oxide layer 60 are less than the disclosed range, there may be insufficient protection for the absorber pattern and the capping layer. If the thicknesses T8 and T9 of the thin oxide layer 60 are greater than the disclosed range, control over fine pattern details and pattern resolution may be lost.

[0096] In some embodiments, the ratio of the thicknesses T8, T9 of the oxide layer 60 to the distance W9 separating adjacent features in the pattern 52 formed in the absorption layer is in the range of about 0.005 to about 0.24, and in other embodiments, it is in the range of about 0.01 to about 0.1. Outside the disclosed range, insufficient protection of the oxide layer or inadequate mask pattern resolution may exist for the oxide thickness / interval distance between adjacent pattern features.

[0097] In some embodiments, a black boundary is formed around a patterned absorption layer at the periphery of the photomask. For example... Figure 20 As shown, a second photoresist layer 70 is formed over the absorber layer 25 and the thin oxide layer 60, thereby filling the pattern 52 in the absorber layer 25. The second photoresist layer 70 is selectively exposed to photochemical radiation, such as an electron beam, ion beam, or UV radiation. The selectively exposed second photoresist layer 70 is developed to form the pattern 55 in the second photoresist layer 70, such as... Figure 21 As shown. Pattern 55 corresponds to the black boundary surrounding the circuit pattern. The black boundary is a frame-shaped area created by removing all layers from the area surrounding the circuit pattern on the EUV photomask. When the EUV photomask is printed on the wafer, the black boundary pattern prevents exposure of adjacent fields. In some embodiments, the width of the black boundary is in the range of about 1 mm to about 5 mm.

[0098] Next, in some embodiments, the pattern 55 in the second photoresist layer 70 is extended into the absorption layer 25, the capping layer 20, and the multilayer 15, thereby forming a pattern 57 on the portion of the exposed substrate 10, such as... Figure 22 As shown. Pattern 57 can be formed by etching using one or more suitable wet or dry etchants that selectively etch each layer. In some embodiments, plasma dry etching is used.

[0099] Then, the second photoresist layer 70 is removed using a suitable photoresist stripper to expose the upper surface of the thin oxide layer 60, thereby forming a photomask 75 with circuit pattern 52 and black boundary pattern 57, as shown. Figure 23 As shown.

[0100] It can also be done in Figures 4 to 11 In the embodiments, black boundaries are formed in the photomask. Furthermore, black boundaries can be formed in one or more of the photomask comprising oxide layer 27, intermediate layer 22, and substrate protection layer 12.

[0101] Embodiments of this disclosure provide 95% to 100% organic contaminant removal efficiency while maintaining high reflectivity of EUV photomasks 75 and 85. For example, in some embodiments, the reflectivity loss of the photomask is less than 0.2% per 10 cleaning cycles. In some embodiments, the initial average reflectivity of the EUV photomasks 75 and 85 according to this disclosure is improved by 2% compared to EUV photomasks manufactured by existing methods. In some embodiments, photomasks 75 and 85 have an average extreme ultraviolet (EUV) reflectivity of 65.1 ± 1%. The average EUV reflectivity is determined by averaging the reflectivity measured at 25 locations on the mask.

[0102] The effects of the second plasma treatment can be detected in photomasks 75 and 85 using time-of-flight secondary ion mass spectrometry (ToF-SIMS). ToF-SIMS analysis shows that photomasks fabricated according to embodiments of this disclosure can increase the hydrogen concentration on the ruthenium and silicon surfaces by up to two times compared to photomasks fabricated by existing methods, while reducing the oxygen concentration by up to three times. Notably, the hydrogen observed in the multilayered first silicon layer region is attributed to plasma penetration, a phenomenon occurring during the interaction between the plasma and the metal surface. The plasma penetration depth varies depending on the material. In this embodiment, hydrogen radicals penetrate through the ruthenium layer to the surface of the silicon layer.

[0103] In some embodiments, a critical dimension (CD) offset / nm of the patterned photomask manufactured according to this disclosure was observed: during the pre-processing phase, this value was approximately 0.07 ± 0.01 for both positive chemical amplification photoresist (PCAR) and negative chemical amplification photoresist (NCAR); while during the post-processing phase, the CD offset / nm for both PCAR and NCAR photoresists was ≤ 0.04. This process difference observed during the pre-processing and post-processing phases is attributed to the varying sulfuric acid content in the sulfuric acid peroxide mixture; higher sulfuric acid content results in a smaller CD offset / nm. For example, in some embodiments, the H2SO4:H2O2 ratio was approximately 10:1 in the pre-processing phase, while in the post-processing phase, the H2SO4:H2O2 ratio was greater than approximately 10:1. In some embodiments, the ratio in the post-processing phase was approximately 19:1. CD measurements were performed using a CD scanning electron microscope metrology tool that measures the lines and / or spaces of the patterned mask.

[0104] The ruthenium durability of the cap layer 20 is determined by subjecting masks 75 and 85 to an etching gas (e.g., xenon difluoride) for a series of etching cycles at an etching rate of about 0.1 to about 0.3 nm / cycle for about 3 to 4 minutes, with pauses of about 30 to 60 seconds between etching cycles. Analysis of the ruthenium durability of the cap layer of masks 75 and 85 manufactured according to this disclosure shows a significant improvement in durability compared to masks manufactured by existing methods.

[0105] Figure 24 A flowchart of a method 2400 for manufacturing an EUV mask according to an embodiment of the present disclosure is shown. In operation S2405, a reflective multilayer stack 15, a cap layer 20, an absorber layer 25, and a hard mask layer 30 are sequentially formed on a substrate 10. In operation S2410, a photoresist layer 35 is formed on the hard mask layer. In operation S2415, the photoresist layer 35 is patterned, and in operation S2420, the hard mask layer 30 is etched to form a hard mask. In some embodiments, in operation S2425, the absorber layer 25 is etched to form a patterned absorber layer using the hard mask as an etch mask. In operation S2430, the patterned photoresist layer and the hard mask are removed. In some embodiments, in operation S2455, the patterned photoresist layer is stripped using a suitable photoresist stripper, and the hard mask is removed by etching. In operation S2435, a first plasma treatment is performed using a plasma of a mixture of oxygen and water. In some embodiments, the water is water vapor. In some embodiments, in operation S2460, the first plasma treatment forms an oxide layer on the absorber layer and the cap layer. After the first plasma treatment, in operation S2440, oxygen and water in the treatment chamber are purged using a mixture of hydrogen and an inert gas. In some embodiments, a hydrogen and inert gas stream flows through the treatment chamber. After purging the treatment chamber, in operation S2445, a second plasma treatment is performed using a mixture of hydrogen and an inert gas. In some embodiments, the inert gas used in the second plasma treatment is the same as the inert gas used in purging operation S2440. In some embodiments, the inert gas is helium. In some embodiments, the second plasma treatment is an inductively coupled plasma treatment, as in operation S2465. In some embodiments, as in operation S2470, the inductively coupled plasma treatment is performed without applying bias power. In some embodiments, the source power for the inductively coupled plasma is in the range of 500W to 3000W, as in operation S2475. After performing the second plasma treatment, a wet cleaning operation is performed in operation S2450.

[0106] Figure 25A flowchart of a method 2500 for manufacturing a photomask according to an embodiment of the present disclosure is shown. In operation S2505, a multilayer stack 15 of alternating molybdenum and silicon layers is formed. In operation S2510, a capping layer 20 is formed on the multilayer stack 15. Then, in operation S2515, an absorption layer 25 is formed on the capping layer 20, and in operation S2520, a hard mask layer 30 is formed on the absorption layer 25. In operation S2525, the hard mask layer 30 is patterned to form a patterned hard mask. In operation S2530, patterns 41, 42 in the hard mask 30 are extended into the absorption layer 25 to form a patterned absorption layer 25 exposing portions of the capping layer 20. Next, in operation S2535, the hard mask is removed. Then, in operation S2540, an oxide layer is formed on the exposed portions of the patterned absorption layer 25 and the capping layer 20. In operation S2545, plasma treatment is performed using a mixture of hydrogen and an inert gas. Following the plasma treatment, a wet cleaning operation is performed in operation S2550. In some embodiments, in operation S2555, photomasks 75 and 85 are exposed to a solution comprising sulfuric acid and hydrogen peroxide.

[0107] Figure 26A flowchart of a method 2600 for manufacturing a photomask according to an embodiment of the present disclosure is shown. In operation S2605, a hard mask layer 30 is formed on a photomask preform 5. In some embodiments, the photomask preform includes: a multilayer stack 15 of alternating first and second layers disposed on a substrate 10, wherein the first and second layers are made of different materials; a cap layer 20 disposed on the multilayer stack 15, wherein the cap layer is made of a different material than the first and second layers; and an absorption layer 25 disposed on the cap layer 20, wherein the absorption layer 25 is made of a different material than the cap layer 20. In operation S2610, the hard mask layer 30 is patterned to form a patterned hard mask. In operation S2615, the absorption layer 25 is etched using the patterned hard mask 30 to extend the patterns 41, 42 in the hard mask into the absorption layer to form the patterned absorption layer 25. Then, in operation S2620, the hard mask is removed. In operation S2625, a first plasma 65 of oxygen and water is applied to the patterned absorber layer 25 in the processing chamber. After applying the first plasma 65, in operation S2630, the processing chamber is purged using a mixture of hydrogen and helium. After purging the processing chamber, in operation S2635, a second plasma 80 of a mixture of hydrogen and helium is applied to the patterned absorber layer 25. In some embodiments, the second plasma 80 is an inductively coupled plasma, as in operation S2645. In some embodiments, as in operation S2650, the inductively coupled plasma 80 is applied without bias power. After applying the second plasma 80, a wet cleaning operation S2640 is performed on the photomasks 75, 85. In some embodiments, the wet cleaning operation S2640 includes exposing the photomasks 75, 85 to a solution comprising sulfuric acid and hydrogen peroxide, as in operation S2655.

[0108] Figure 27A flowchart of a method 2700 for manufacturing a photomask according to an embodiment of the present disclosure is shown. In operation S2705, a multilayer stack 15 of alternating molybdenum and silicon layers is formed. In operation S2710, a capping layer 20 is formed on the multilayer stack 15. Then, in operation S2715, an absorption layer 25 is formed on the capping layer 20, and in operation S2720, a hard mask layer 30 is formed on the absorption layer 25. In operation S2725, the hard mask layer 30 is patterned to form a patterned hard mask. In operation S2730, the patterns 41, 42 in the hard mask 30 are extended into the absorption layer 25 to form a patterned absorption layer 25 exposing portions of the capping layer 20. Next, in operation S2735, the hard mask is removed. Then, in operation S2540, a reducing agent 90 is applied to the exposed portions of the patterned absorption layer 25 and the capping layer 30. The reducing agent includes at least one selected from hydrogen plasma, hydrogen, carbon monoxide, sodium borohydride, lithium aluminum hydride, hydrazine, hydrogen peroxide, sulfur dioxide, sodium dithionite, or ascorbic acid. Then, in operation S2745, a wet cleaning operation is performed.

[0109] Figure 28A , Figure 28B , Figure 28C and Figure 28D The sequential manufacturing operations of a method for manufacturing a semiconductor device according to embodiments of the present disclosure are illustrated. A semiconductor substrate or other suitable substrate is provided to be patterned to form an integrated circuit thereon. In some embodiments, the semiconductor substrate comprises silicon. Alternatively or additionally, the semiconductor substrate comprises germanium, silicon-germanium, or other suitable semiconductor materials, such as group III-V semiconductor materials.

[0110] like Figure 28A As shown, a target layer (TL) to be patterned is formed on a semiconductor substrate. In some embodiments, the target layer is the semiconductor substrate. In some embodiments, the target layer includes a conductive layer such as a metal layer or a polysilicon layer; a dielectric layer such as silicon oxide, silicon nitride, SiON, SiOC, SiOCN, SiCN, hafnium oxide, or aluminum oxide; or a semiconductor layer such as an epitaxially formed semiconductor layer. In some embodiments, the target layer is formed on an underlying structure (e.g., an isolation structure), transistor, or wiring. Figure 28A As shown, a photoresist layer PR is formed on the target layer TL. The photoresist layer is sensitive to radiation from the exposure source during subsequent photolithography processes. In this embodiment, the photoresist layer is sensitive to EUV light used in the photolithography process. The photoresist layer can be formed on the target layer by spin coating or other suitable techniques. The coated photoresist layer can be further baked to remove solvent from the photoresist layer.

[0111] The photoresist layer was then patterned using an EUV reflective mask fabricated according to the method disclosed herein, such as... Figure 28B As shown, patterning of the photoresist layer involves performing a photolithography process using an EUV mask through an EUV exposure system. During the exposure process, an integrated circuit (IC) design pattern defined on the EUV mask is imaged onto the photoresist layer to form a potential pattern thereon.

[0112] Patterning of the photoresist layer also includes: developing and exposing the photoresist layer to form a patterned photoresist layer with one or more openings, such as... Figure 28C As shown. In one embodiment where the photoresist layer is a positive photoresist layer, the exposed portions of the photoresist layer are removed during the development process. In other embodiments, the photoresist layer is a negative photoresist layer, and the unexposed portions of the photoresist layer are removed during the development process. Patterning of the photoresist layer may also include other process steps, such as various baking steps at different stages. For example, a post-exposure baking (PEB) process may be performed after the photolithography exposure process and before the development process.

[0113] like Figure 28C As shown, a patterned photoresist layer is used as an etching mask to pattern the target layer TL. In some embodiments, patterning the target layer includes applying an etching process to the target layer using the patterned photoresist layer as an etching mask. The portion of the target layer exposed within the openings of the patterned photoresist layer is etched, while the remaining portion is not etched. Furthermore, the patterned photoresist layer can be removed by wet stripping or plasma ashing, such as... Figure 28D As shown.

[0114] Embodiments of this disclosure prevent critical dimension loss during photomask fabrication and cleaning operations. Embodiments of this disclosure minimize material loss (such as chromium and ruthenium) during mask cleaning and simultaneously remove hydrocarbon contaminants, thereby providing improved EUV reflectivity. Embodiments of this disclosure provide twice the window expansion in the photomask patterning process during semiconductor device fabrication operations, extending photomask lifetime, improving hydrocarbon defect removal, and optimizing and controlling EUV reflectivity. Embodiments of this disclosure also provide durability of the capping layer when exposed to etching cycles. Embodiments of this disclosure also prevent watermark defects caused by the cleaning process. Embodiments of this disclosure provide 95% to 100% organic contaminant removal efficiency. Embodiments of this disclosure maintain high reflectivity of the EUV photomask. For example, in some embodiments, the reflectivity loss of the photomask is less than 0.2% per 10 cleaning cycles. In some embodiments, the EUV photomask according to this disclosure has an initial average reflectivity that is 2% higher than that of EUV photomasks fabricated by existing methods. In some embodiments, the photomask has an average extreme ultraviolet reflectance of 65.1 ± 1%. In some embodiments, no significant critical size change (e.g., -≤0.3 nm) occurs after 2 to 4 consecutive cycles of the first and second plasma treatments. In some embodiments, there is no significant damage to the ruthenium capping layer. In some embodiments, the application of a reducing agent and subsequent wet cleaning operations provide removal of: organic contaminants; metallic contaminants, including Cr, Ta, Al, Fe, Na, Mg, and Ru; and non-metallic contaminants, including Si and S.

[0115] In some embodiments, the methods disclosed herein provide improved resolution of the circuit pattern formed in the absorption layer. Embodiments of this disclosure provide improved mask critical dimension (CD) uniformity and prevent mask-induced CD profile attenuation.

[0116] It is understood that not all advantages need to be discussed herein, no particular advantage is necessary for all embodiments or examples, and other embodiments or examples may provide different advantages.

[0117] According to embodiments of this disclosure, a method for manufacturing an extreme ultraviolet (EUV) mask includes: sequentially forming a reflective multilayer stack, a capping layer, an absorber layer, and a hard mask layer on a substrate; forming a photoresist layer on the hard mask layer and patterning the photoresist layer; etching the hard mask layer to form a hard mask; etching the absorber layer to form a patterned absorber layer; removing the patterned photoresist layer and the hard mask; performing a first plasma treatment using a plasma formed from a mixture of oxygen and water; purging the plasma using a mixture of H2 and an inert gas; performing a second plasma treatment using a plasma formed from a mixture of H2 and an inert gas; and performing a wet cleaning operation. In embodiments, removing the patterned photoresist layer and the hard mask includes stripping the photoresist layer and etching the hard mask. In embodiments, the wet cleaning operation is performed after performing the second plasma treatment. In embodiments, the second plasma treatment is an inductively coupled plasma (ICP) treatment. In embodiments, the ICP treatment is performed without applying bias power. In one embodiment, the power applied during the second plasma treatment is in the range of 500 W to 4000 W. In one embodiment, the concentration of H2 in the mixture of H2 and inert gas is in the range of 1 mol.% to 5 mol.%. In one embodiment, an oxide layer is formed on the patterned absorber layer and capping layer during the first plasma treatment. In one embodiment, the ratio of the thickness of the oxide layer after the wet cleaning operation to the thickness of the oxide layer before the wet cleaning operation is in the range of 0.8 to 1.0.

[0118] According to another embodiment of this disclosure, a method of manufacturing a photomask includes: forming a multilayer stack of alternating molybdenum and silicon layers on a substrate; forming a capping layer on the multilayer stack and an absorption layer on the capping layer; forming a hard mask layer on the absorption layer and patterning the hard mask layer to form a patterned hard mask; extending the pattern in the hard mask into the absorption layer to form a patterned absorption layer exposing portions of the capping layer; removing the hard mask; forming an oxide layer on the exposed portions of the patterned absorption layer and capping layer; performing a plasma treatment using a plasma formed from a mixture of H2 and an inert gas, performing a wet cleaning operation. In an embodiment, the capping layer comprises ruthenium or a ruthenium alloy. In an embodiment, the absorption layer comprises chromium or a chromium compound. In an embodiment, the wet cleaning operation is performed after the plasma treatment. In an embodiment, the wet cleaning operation includes exposing the photomask to a solution comprising sulfuric acid and hydrogen peroxide. In an embodiment, the concentration of H2 in the mixture used to form the plasma is in the range of 1 mol.% to 5 mol.%.

[0119] Another embodiment of this disclosure is a method for manufacturing a photomask, comprising forming a hard mask layer on a photomask preform. The photomask preform includes: a multilayer stack of alternating first and second layers disposed on a substrate, wherein the first and second layers are made of different materials; a cap layer disposed on the multilayer stack, wherein the cap layer is made of a different material than the first and second layers; and an absorber layer disposed on the cap layer, wherein the absorber layer is made of a different material than the cap layer. The hard mask layer is patterned to form a patterned hard mask. The patterned hard mask is used as an etch mask to etch the absorber layer to extend the pattern in the hard mask into the absorber layer to form a patterned absorber layer. The patterned absorber layer exposes portions of the cap layer. The hard mask is removed. A first plasma formed of a mixture of oxygen and water is applied to the patterned absorber layer in a processing chamber. After applying the first plasma, the processing chamber is purged with a mixture of H2 and He. After purging the processing chamber, a second plasma formed of a mixture of H2 and He is applied to the patterned absorber layer. After applying the second plasma, a wet cleaning operation is performed on the photomask. In this embodiment, the second plasma is an inductively coupled plasma. In this embodiment, the inductively coupled plasma treatment is performed without applying bias power. In this embodiment, the wet cleaning operation includes exposing a photomask to a solution comprising sulfuric acid and hydrogen peroxide. In this embodiment, the concentration of H2 in the mixture used to form the second plasma is in the range of 1 mol.% to 5 mol.%.

[0120] Another embodiment of this disclosure is a method for manufacturing a photomask, comprising forming a multilayer stack of alternating molybdenum and silicon layers on a substrate. A capping layer is formed on the multilayer stack. An absorption layer is formed on the capping layer. A hard mask layer is formed on the absorption layer. The hard mask layer is patterned to form a patterned hard mask. The pattern in the hard mask is extended into the absorption layer to form a patterned absorption layer exposing portions of the capping layer, and the hard mask is removed. After removing the hard mask, a reducing agent is applied to the exposed portions of the patterned absorption layer and the capping layer, and a wet cleaning operation is performed. In embodiments, the reducing agent includes at least one selected from hydrogen plasma, hydrogen, carbon monoxide, sodium borohydride, lithium aluminum hydride, hydrazine, hydrogen peroxide, sulfur dioxide, sodium dithionite, or ascorbic acid. In embodiments, the reducing agent is dissolved in a solvent or an inert gas. In embodiments, the capping layer includes ruthenium or a ruthenium alloy. In embodiments, the absorption layer includes chromium or a chromium compound. In embodiments, the wet cleaning operation is performed after the application of the reducing agent.

[0121] Another embodiment of this disclosure is a reflective photomask comprising a reflective multilayer stack disposed on a substrate, wherein the reflective multilayer stack includes a plurality of alternating first and second layers. A cap layer is disposed on the reflective multilayer stack, and a patterned absorption layer is disposed on the cap layer. The reflective photomask has an average extreme ultraviolet reflectance of 65.1 ± 1%. In an embodiment, the reflective multilayer stack includes 40 ± 1 pairs of first and second layers. In an embodiment, the reflective photomask includes an oxide layer disposed on the patterned absorption layer. In an embodiment, the patterned absorption layer is made of Cr, CrN, CrON, or CrCON. In an embodiment, the cap layer is made of ruthenium, a ruthenium alloy, or a ruthenium-based oxide. In an embodiment, the reflective photomask includes a black boundary that exposes the substrate surrounding a patterned region of the photomask. In an embodiment, the reflective photomask includes an intermediate layer disposed between the cap layer and the patterned absorption layer, wherein the intermediate layer is made of a different material than the cap layer and the patterned absorption layer.

[0122] Another embodiment of this disclosure is a reflective photomask comprising a multilayer stack including multiple pairs of alternating first and second material layers disposed on a substrate, wherein the first material has a different composition than the second material layers. A capping layer having a different composition than the first and second materials is disposed on the multilayer stack. An absorber layer having a different composition than the capping layer is disposed on the capping layer, wherein a pattern is formed in the absorber layer. An oxide layer is disposed on the absorber layer. The thickness of the oxide layer is in the range of 2 nm to 3.5 nm. In an embodiment, the pattern comprises adjacent oxide-covered pattern features spaced apart from each other in the range of 25 nm to 100 nm. In an embodiment, the multilayer stack includes 40 ± 1 pairs of molybdenum and silicon layers. In an embodiment, the absorber layer is made of Cr, CrN, CrON, or CrCON. In an embodiment, the capping layer is made of ruthenium, a ruthenium alloy, or a ruthenium-based oxide. In an embodiment, the reflective photomask includes trenches that expose the substrate surrounding the pattern. In one embodiment, the reflective photomask includes an intermediate layer disposed between a cap layer and an absorber layer, wherein the intermediate layer is made of a different material than the cap layer and the absorber layer.

[0123] Another embodiment of this disclosure is a photomask comprising a multilayer stack including multiple pairs of alternating first and second layers, wherein the first layer is made of a different material than the second layer. A cap layer made of a different material than the first and second layers is disposed on the multilayer stack. An absorber layer made of a different material than the cap layer is disposed on the cap layer, wherein a pattern is formed in the absorber layer. An oxide layer is disposed on the absorber layer. The ratio of the thickness of the oxide layer to the distance separating adjacent features in the pattern formed in the absorber layer is in the range of 0.005 to 0.24. In one embodiment, the oxide layer is disposed on the top surface and sidewalls of the pattern formed in the absorber layer and on the portion of the cap layer between the pattern features in the absorber layer. In an embodiment, the multilayer stack includes 40 ± 1 pairs of molybdenum and silicon layers. In an embodiment, the absorber layer is made of Cr, CrN, CrON, or CrCON. In an embodiment, the cap layer is made of ruthenium, a ruthenium alloy, or a ruthenium-based oxide. In one embodiment, the photomask includes an intermediate layer disposed between a cap layer and an absorber layer, wherein the intermediate layer is made of a different material than the cap layer and the absorber layer.

[0124] The foregoing disclosure outlines features of several embodiments or examples, enabling those skilled in the art to better understand various aspects of this disclosure. Those skilled in the art should understand that they can readily use this disclosure as a basis for designing or modifying other processes and structures to implement the same purposes and / or achieve the same advantages of the embodiments or examples described herein.

[0125] Example 1 is a method for manufacturing an extreme ultraviolet (EUV) mask, comprising: sequentially forming a reflective multilayer stack, a capping layer, an absorber layer, and a hard mask layer on a substrate; forming a photoresist layer on the hard mask layer; patterning the photoresist layer; etching the hard mask layer to form a hard mask; etching the absorber layer to form a patterned absorber layer; removing the patterned photoresist layer and the hard mask; performing a first plasma treatment using a plasma formed from a mixture of oxygen and water; purging the plasma using a mixture of H2 and an inert gas; performing a second plasma treatment using a plasma formed from a mixture of H2 and an inert gas; and performing a wet cleaning operation.

[0126] Example 2 is the method of Example 1, wherein removing the patterned photoresist layer and the hard mask includes: stripping the photoresist layer and etching the hard mask.

[0127] Example 3 is the method described in Example 1, wherein the wet cleaning operation is performed after the second plasma treatment is performed.

[0128] Example 4 is the method described in Example 1, wherein the second plasma treatment is an inductively coupled plasma treatment.

[0129] Example 5 is the method described in Example 4, wherein the inductively coupled plasma treatment is performed without applying bias power.

[0130] Example 6 is the method described in Example 4, wherein the power applied during the second plasma treatment is in the range of 500W to 4000W.

[0131] Example 7 is the method described in Example 1, wherein the concentration of H2 in the mixture of H2 and inert gas is in the range of 1 mol.% to 5 mol.%.

[0132] Example 8 is the method of Example 1, wherein, during the first plasma treatment, an oxide layer is formed on the patterned absorption layer and the capping layer.

[0133] Example 9 is the method described in Example 8, wherein the ratio of the thickness of the oxide layer after the wet cleaning operation to the thickness of the oxide layer before the wet cleaning operation is in the range of 0.8 to 1.0.

[0134] Example 10 is a method for manufacturing a photomask, comprising: forming a multilayer stack of alternating molybdenum and silicon layers on a substrate; forming a cap layer on the multilayer stack; forming an absorption layer on the cap layer; forming a hard mask layer on the absorption layer; patterning the hard mask layer to form a patterned hard mask; extending the pattern in the hard mask into the absorption layer to form a patterned absorption layer, the patterned absorption layer exposing a portion of the cap layer; removing the hard mask; after removing the hard mask, applying a reducing agent to the exposed portions of the patterned absorption layer and the cap layer; and performing a wet cleaning operation.

[0135] Example 11 is the method of Example 10, wherein the reducing agent comprises at least one of hydrogen plasma, hydrogen, carbon monoxide, sodium borohydride, lithium aluminum hydride, hydrazine, hydrogen peroxide, sulfur dioxide, sodium dithionite, or ascorbic acid.

[0136] Example 12 is the method of Example 11, wherein the reducing agent is dissolved in a solvent or an inert gas.

[0137] Example 13 is the method described in Example 10, wherein the cap layer comprises ruthenium or a ruthenium alloy.

[0138] Example 14 is the method of Example 10, wherein the absorbent layer comprises chromium or a chromium compound.

[0139] Example 15 is the method described in Example 10, wherein the wet cleaning operation is performed after the reducing agent is applied.

[0140] Example 16 is a reflective photomask comprising: a reflective multilayer stack disposed on a substrate, wherein the reflective multilayer stack includes a plurality of alternating first and second layers; a cap layer disposed on the reflective multilayer stack; and a patterned absorption layer disposed on the cap layer, wherein the reflective photomask has an average extreme ultraviolet reflectivity of 65.1 ± 1%.

[0141] Example 17 is the reflective photomask described in Example 16, wherein the reflective multilayer stack includes 40±1 pairs of first and second layers.

[0142] Example 18 is the reflective photomask described in Example 16, further comprising: an oxide layer disposed on the patterned absorption layer.

[0143] Example 19 is the reflective photomask described in Example 16, further comprising: a black boundary that exposes the substrate and surrounds a patterned area of ​​the photomask.

[0144] Example 20 is the reflective photomask described in Example 16, further comprising: an intermediate layer disposed between the cap layer and the patterned absorption layer, wherein the intermediate layer is made of a different material from the cap layer and the patterned absorption layer.

Claims

1. A method for manufacturing an extreme ultraviolet (EUV) mask, comprising: A reflective multilayer stack, a capping layer, an absorption layer, and a hard mask layer are sequentially formed on the substrate. A photoresist layer is formed on the hard mask layer; Pattern the photoresist layer; Etch the hard mask layer to form a hard mask; Etching the absorption layer to form a patterned absorption layer; Remove the patterned photoresist layer and the hard mask; The first plasma treatment is performed using plasma formed from a mixture of oxygen and water; The plasma was purged using a mixture of H2 and an inert gas; The second plasma treatment is performed using plasma formed from a mixture of H2 and inert gas; as well as Perform wet cleaning operations.

2. The method according to claim 1, wherein, Removing the patterned photoresist layer and the hard mask includes: stripping the photoresist layer and etching the hard mask.

3. The method according to claim 1, wherein, The wet cleaning operation is performed after the second plasma treatment.

4. The method according to claim 1, wherein, The second plasma treatment is inductively coupled plasma treatment.

5. The method according to claim 4, wherein, The inductively coupled plasma treatment is performed without applying bias power.

6. The method according to claim 4, wherein, The power applied during the second plasma treatment is in the range of 500W to 4000W.

7. The method according to claim 1, wherein, The concentration of H2 in the mixture of H2 and inert gas is in the range of 1 mol.% to 5 mol.%.

8. The method according to claim 1, wherein, During the first plasma treatment, an oxide layer is formed on the patterned absorber layer and the capping layer.

9. A method for manufacturing a photomask, comprising: A multilayer stack of alternating molybdenum and silicon layers is formed on the substrate; A cap layer is formed on top of the multi-layered stack; An absorbent layer is formed on top of the cap layer; A hard mask layer is formed on top of the absorption layer; Pattern the hard mask layer to form a patterned hard mask; The pattern in the hard mask is extended into the absorbent layer to form a patterned absorbent layer that exposes a portion of the cap layer; Remove the hard mask; After removing the hard mask, a reducing agent is applied to the exposed portions of the patterned absorption layer and the capping layer; as well as Perform wet cleaning operations.

10. A reflective photomask, comprising: Reflective multilayer stacks are disposed on a substrate. The reflective multilayer stack includes multiple alternating first and second layers; A cap layer is disposed on the reflective multilayer stack; and A patterned absorption layer is disposed on the cap layer. The reflective photomask has an average extreme ultraviolet radiation reflectivity of 65.1±1%.

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