Lithography mask and method of manufacturing

Abstract

One embodiment of the present disclosure relates to a lithography mask and a method of manufacturing the same. The method includes forming a multilayer reflective structure on a substrate. A capping layer is formed over the multi-layer reflective structure. A buffer layer is formed over the capping layer, and an absorber layer is formed over the buffer layer. The absorption layer at least comprises a first absorption layer and a second absorption layer, each absorption layer comprises non-alloy elements, and the first absorption layer and the second absorption layer are made of different non-alloy elements.

Description

Technical Field

[0001] One embodiment disclosed herein relates to a photomask and a method for manufacturing the photomask. Background Technology

[0002] The semiconductor integrated circuit (IC) industry has experienced rapid growth. Advances in IC materials and design technologies have resulted in generation after generation of ICs, each generation smaller and more complex than the last. However, these advancements have increased the complexity of IC fabrication and manufacturing, requiring similar developments in these areas to achieve the same level of progress. Throughout IC development, functional density (the number of interconnects per unit wafer area) has generally increased, while geometric dimensions (the smallest element (or line) that can be manufactured using a specific process) have decreased.

[0003] As semiconductor device sizes continue to shrink, such as into the nanometer (nm) node, traditional photolithography techniques suffer from optical limitations, leading to resolution issues and potentially failing to achieve the required lithographic performance. In contrast, extreme ultraviolet (EUV) lithography can achieve even smaller device sizes. However, existing EUV lithography technologies may still face certain challenges. For example, the material used in the absorption layer of current EUV masks may be too thick, potentially reducing the lithographic performance of the EUV mask.

[0004] Therefore, although existing EUV lithography systems and methods are generally sufficient for their intended use, there is still room for improvement. Summary of the Invention

[0005] According to some embodiments disclosed herein, a method for manufacturing a photolithographic mask includes forming a multilayer reflective structure on a substrate, forming a capping layer on the multilayer reflective structure, forming a buffer layer on the capping layer, and forming an absorption layer on the buffer layer. The absorption layer includes at least one first absorption layer and one second absorption layer, each comprising a non-alloy component selected from platinum (Pt), palladium (Pd), gold (Au), iridium (Ir), osmium (Os), rhodium (Rh), ruthenium (Ru), indium (In), tellurium (Te), chromium (Cr), tungsten (W), molybdenum (Mo), tantalum (Ta), nickel (Ni), cobalt (Co), or titanium (Ti), and the first absorption layer and the second absorption layer are made of different non-alloy components.

[0006] According to some embodiments disclosed herein, a method for manufacturing a photomask includes forming a multilayer reflective structure on a substrate, forming a capping layer on the multilayer reflective structure, forming a buffer layer on the capping layer, and forming a plurality of absorption layers on the buffer layer. The absorption layers include at least one first absorption layer and one second absorption layer, each comprising a non-alloy component selected from platinum (Pt), palladium (Pd), gold (Au), iridium (Ir), osmium (Os), rhodium (Rh), ruthenium (Ru), indium (In), tellurium (Te), chromium (Cr), tungsten (W), molybdenum (Mo), tantalum (Ta), nickel (Ni), cobalt (Co), or titanium (Ti). The first and second absorption layers are made of different non-alloy components; a plurality of hard masks are formed on the absorption layers; a photoresist layer is formed on the hard masks; and a patterning process is performed on the photomask to obtain a patterned photomask.

[0007] According to some embodiments disclosed herein, a photolithography mask includes a substrate, a multilayer reflective structure, a capping layer, a buffer layer, and an absorption layer. The multilayer reflective structure is disposed on the substrate. The capping layer is disposed on the multilayer reflective structure. The buffer layer is disposed on the capping layer. The absorption layer is disposed on the buffer layer. The absorption layer includes at least one first absorption layer and one second absorption layer, each comprising a non-alloy component selected from platinum (Pt), palladium (Pd), gold (Au), iridium (Ir), osmium (Os), rhodium (Rh), ruthenium (Ru), indium (In), tellurium (Te), chromium (Cr), tungsten (W), molybdenum (Mo), tantalum (Ta), nickel (Ni), cobalt (Co), or titanium (Ti), wherein the first absorption layer and the second absorption layer are made of different non-alloy components. Attached Figure Description

[0008] Aspects of one embodiment of this disclosure can be best understood by reading the following detailed description in conjunction with the accompanying drawings. It should be noted that, according to industry standard practice, the various features are not drawn to scale. In fact, for clarity of discussion, the dimensions of the various features may be arbitrarily increased or decreased.

[0009] Figure 1 A schematic diagram of a photolithography system constructed according to some embodiments disclosed herein;

[0010] Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 and Figure 11 Cross-sectional views illustrating various steps in the fabrication of a photolithographic mask according to some embodiments disclosed herein;

[0011] Figure 12 , Figure 13 , Figure 14 , Figure 15 , Figure 16 , Figure 17 , Figure 18 , Figure 19 , Figure 20 , Figure 21 and Figure 22 Cross-sectional views illustrating various steps in fabricating a patterned photomask according to some embodiments of this disclosure;

[0012] Figure 23 A method for manufacturing a photomask is illustrated according to some embodiments disclosed herein;

[0013] Figure 24 Methods for manufacturing patterned photomasks are illustrated according to some embodiments disclosed herein.

[0014] [Symbol Explanation]

[0015] 10: Photolithography System

[0016] 12: Radiation source

[0017] 14:Illuminator

[0018] 16: Shielding Platform

[0019] 18: EUV lithography mask

[0020] 20:POB

[0021] 22: Modulator

[0022] 24: Plane

[0023] 26: Target

[0024] 28:Substrate table

[0025] 30:Substrate

[0026] 32: Conductive layer

[0027] 34: Multi-layered reflection structure

[0028] 35: Cap layer

[0029] 37: Buffer layer

[0030] 39, 39a, 39b, 39c, 39d: Absorption layers

[0031] 41,43: Interdiffusion layer

[0032] 44: Side view

[0033] 45, 45a, 45b, 45c, 45d: Hard mask

[0034] 47: Photoresist layer

[0035] 47a: Part

[0036] 49: Opening

[0037] S2301, S2303, S2305, S2307, S2401, S2403, S2405, S2407, S2409, S2411, S2413: Steps Detailed Implementation

[0038] The following disclosure provides many different implementations or examples for performing the different features of the main content provided. Specific components and configuration examples are described below to simplify one implementation of this disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature on or over a second feature described may include implementations where the first and second features are formed in direct contact, and may also include implementations where additional features may be formed within the first and second features so that the first and second features are not in direct contact. Furthermore, one implementation of this disclosure may repeat references to numbers and / or letters in various examples. This repetition is for simplification or clarity and does not specify the relationship between the various implementations and / or configurations discussed.

[0039] Furthermore, spatially related terms, such as "below," "lower part," "above," and "upper part," are used here to simply describe the relationship of one element or feature to other elements or features illustrated in the diagram. Spatially related terms are intended to include the orientation of different devices in use or operation. Instruments may have other orientations (rotated 90 degrees or other orientations), and spatially related descriptions used here are subject to interpretation.

[0040] EUV lithography is widely used due to its ability to achieve miniaturized semiconductor devices. However, conventional systems and methods for performing EUV lithography still face various challenges. For example, conventional EUV systems employ a lithographic mask configured for EUV lithography. In addition, the EUV lithographic mask includes an absorption layer that absorbs EUV light and minimizes reflection to ensure the contrast between the patterned image and the multilayer coating. The EUV mask patterning process depends on the correct selection of the EUV mask's absorbing material, which directly impacts mask quality, such as critical dimension (CD) control. Some conventional EUV lithographic masks may use absorption layers that are too thick. If the absorption layer is too thick, for example, between 45 and 70 nm, it is difficult to adjust the refractive index and extinction coefficient values ​​of the EUV mask. Some conventional absorption layers use binary alloy materials, resulting in a thicker absorption layer that makes it difficult to obtain ideal refractive index and extinction coefficient values. Thick absorption layers can be affected by three-dimensional effects of the mask, such as the shadows that occur when EUV light illuminates an EUV mask at a certain angle, leading to asymmetrical shadows and dimensional deviations between features in different directions. Furthermore, thick absorption layers can distort the phase of the incident light, resulting in aberration-like effects. Additionally, thicker absorption layers can allow for greater exposure energy.

[0041] To alleviate the aforementioned problems, one embodiment of this disclosure provides an EUV lithography mask having a multilayer absorption layer comprising pure elements, resulting in a thinner absorption layer. The thinner absorption layer makes it easier to adjust the EUV refractive index and extinction coefficient values. In some embodiments, the material used in the multilayer absorption layer provides a low refractive index to obtain a phase difference close to π (e.g., 1 to 1.2π) between light passing through the absorber region and the open region.

[0042] Furthermore, by utilizing one embodiment of this disclosure, reducing the thickness of the absorption layer helps to reduce the occurrence of three-dimensional effects in the photomask, lower exposure energy, and improve the Normalized Image Log Slope (NILS). NILS is an important indicator for evaluating EUV image quality; it is measured by the steepness of the intensity transition at the edge of the photomask pattern normal, where the steepness directly affects the edge sharpness of the resulting photoresist pattern. Various aspects of one embodiment of this disclosure will be discussed in more detail below with reference to the accompanying drawings.

[0043] The following is for reference Figure 1This paper discusses an EUV lithography system according to one embodiment of the present disclosure. The figures show schematic diagrams of an EUV lithography system 10 constructed according to some embodiments. The EUV lithography system 10, commonly referred to as a scanner, is configured to perform a lithographic exposure process using a corresponding radiation source and exposure mode. The EUV lithography system 10 is designed to expose a photoresist layer by EUV light or EUV radiation. The photoresist layer is a material sensitive to EUV light. The UV lithography system 10 uses a radiation source 12 to generate EUV light, for example, EUV light with a wavelength range of about 1 nm to about 100 nm. In some examples, the radiation source 12 generates EUV light with wavelengths between 10 and 121 nm. Therefore, the radiation source 12 is also referred to as an EUV radiation source 12.

[0044] The lithography system 10 also employs an illuminator 14. In various embodiments, the illuminator 14 includes various refractive optical elements, such as a single lens or a lens system with multiple lenses (area plates), or alternatively, reflective optical elements (for EUV lithography systems), such as a single mirror or a mirror system with multiple mirrors, for guiding light from the radiation source 12 onto the mask stage 16, particularly onto the EUV lithography mask 18 fixed to the mask stage 16. The mask stage 16 is configured to hold the EUV lithography mask 18. In some embodiments, the mask stage 16 includes an electrostatic chuck to hold the EUV lithography mask 18. In this embodiment, the radiation source 12 generates light in the EUV wavelength range, while the illuminator 14 employs reflective optical elements. In some embodiments, the illuminator 14 includes a bipolar illumination assembly.

[0045] In some embodiments, illuminator 14 is operable to configure mirrors to provide appropriate illumination to the EUV lithography mask 18. In one example, the mirrors of illuminator 14 are switchable to reflect EUV light to different illumination positions. In some embodiments, stages preceding illuminator 14 include additional switchable mirrors that are controllable to direct EUV light to illumination positions different from those of the mirrors of illuminator 14. In some embodiments, illuminator 14 is configured to provide on-axis illumination (ONI) to the EUV lithography mask 18. In one example, a disk illuminator 14 with a partial coherence σ of at most 0.3 is employed. In some other embodiments, illuminator 14 is configured to provide off-axis illumination (OAI) to the EUV lithography mask 18. For example, illuminator 14 is a dipole illuminator. In some embodiments, the dipole illuminator has a partial coherence σ of at most 0.3.

[0046] exist Figure 1In the implementation method described herein, the lithography system 10 is an EUV lithography system, and the EUV lithography mask 18 is a reflective mask. In one embodiment of this disclosure, the terms mask, photomask, and mask plate are used interchangeably to refer to the same item. An exemplary structure of the EUV lithography mask 18 is provided for illustration. The EUV lithography mask 18 includes a substrate having a suitable material, such as a low thermal expansion material (LTEM) or fused silica. In various examples, the LTM includes SiO2 doped with TiO2 or other suitable materials having low thermal expansion. In some implementations, the LTM includes 5%-20% by weight of TiO2 and has a coefficient of thermal expansion of less than about 1.0 × 10⁻⁶. -6 / °C. In some implementations, the coefficient of thermal expansion of the TiO2-doped SiO2 material in the LTM changes by less than one part per 6 billion for every 1 degree Celsius change. Of course, other suitable materials with a coefficient of thermal expansion equal to or less than that of TiO2-doped SiO2 can also be considered.

[0047] The EUV lithography mask 18 also includes a multilayer reflective structure deposited on the substrate. The multilayer reflective structure includes multiple film pairs, such as molybdenum-silicon (Mo / Si) film pairs (e.g., a molybdenum layer in each film pair is located above or below a silicon layer). Alternatively, the multilayer reflective structure includes molybdenum-beryllium (Mo / Be) film pairs, or other suitable materials configured to reflect EUV light.

[0048] The EUV lithography mask 18 includes a capping layer disposed on a multilayer reflective structure for protecting the multilayer reflective structure and / or layers beneath it. According to an embodiment of the invention, the capping layer of the EUV lithography mask 18 comprises an amorphous or polycrystalline structure. In some embodiments, the capping layer is formed on the multilayer reflective structure. In other embodiments, the capping layer is formed by first treating the upper surface of the multilayer reflective structure (e.g., with plasma treatment), and then forming the capping layer on the treated surface of the multilayer reflective structure.

[0049] The EUV lithography mask 18 also includes an absorption layer (also called an absorption layer) deposited over the capping layer. The absorption layer is patterned to define a layer of the integrated circuit (IC). Alternatively, another reflective layer is deposited over a multilayer reflective structure and patterned to define a layer of the integrated circuit, thereby forming an EUV phase-shift mask. In one embodiment of this disclosure, the absorption layer is a multilayer structure (e.g., 2, 3, or 4 layers) comprising a low-refractive-index material, which helps to reduce the thickness of the absorption layer, improve NILS, and reduce exposure energy.

[0050] like Figure 1As shown, the lithography system 10 also includes a projection optics module or projection optics box (POB) 20 for imaging the pattern of the EUV lithography mask 18 onto a target 26 (e.g., a semiconductor substrate) fixed on a substrate stage 28. In various embodiments, the POB 20 has refractive optics (e.g., for ultraviolet lithography systems) or reflective optics (e.g., for EUV lithography systems). Light emitted from the EUV lithography mask 18 is diffracted into various diffraction orders and carries an image of the pattern defined on the mask, which is collected by the POB 20. In some embodiments, the POB 20 includes a magnification of less than one (so that the size of the “image” on the target (e.g., target 26 discussed below) is smaller than the size of the corresponding “object” on the mask). The illuminator 14 and the POB 20 are collectively referred to as the optical modules of the lithography system 10.

[0051] The lithography system 10 also includes a pupil phase modulator 22 to modulate the optical phase of light guided from the EUV lithography mask 18, such that the light has a phase distribution on the projection pupil plane 24. In the optical module, there exists a plane whose field distribution corresponds to the Fourier transform of the object (in this example, the EUV lithography mask 18). This plane is called the projection pupil plane. The pupil phase modulator 22 provides a mechanism to modulate the optical phase of light on the projection pupil plane 24. In some embodiments, the pupil phase modulator 22 includes a mechanism for adjusting the mirrors of the POB 20 for phase modulation. In some embodiments, the mirrors of the POB 20 are switchable and controlled to reflect EUV light, thereby modulating the phase of the light passing through the POB 20.

[0052] In some implementations, the pupil phase modulator 22 utilizes a pupil filter placed on the projection pupil plane 24. The pupil filter filters out specific spatial frequency components of EUV light from the EUV lithography mask 18. Specifically, the pupil filter is a phase pupil filter, which functions to modulate the phase distribution of light passing through the POB 20. However, in some lithography systems (e.g., EUV lithography systems), the use of phase pupil filters is limited because the material of the phase pupil filter absorbs EUV light.

[0053] As described above, the lithography system 10 also includes a substrate stage 28 for fixing the target 26 to be patterned, such as a semiconductor substrate. In this embodiment, the semiconductor substrate is a semiconductor wafer, such as a silicon wafer or other type of wafer. The target 26 is coated with a resist layer sensitive to a radiation beam (e.g., EUV light in this embodiment). Various components, including those described above, are integrated together and can be used to perform the lithography exposure process. In some embodiments, the lithography system 10 includes other modules or is integrated (or coupled) with other modules.

[0054] EUV lithography mask 18 and its fabrication method are further described according to some embodiments. In some embodiments, the mask fabrication process includes a blank mask fabrication process and a mask patterning process. In the blank mask fabrication process, a blank mask is formed by depositing a suitable layer (e.g., a reflective multilayer) on a suitable substrate. The blank mask is then patterned in the mask patterning process to realize the desired design of the integrated circuit (IC) layer. The patterned mask is then used to transfer the circuit pattern (e.g., the IC layer design) onto a semiconductor wafer. The pattern is repeatedly transferred onto multiple wafers through various lithography processes. A set of masks is used to construct a complete IC.

[0055] In various implementations, the EUV lithography mask 18 includes suitable structures, such as a binary intensity mask (BIM) and a phase-shifting mask (PSM). An example BIM includes absorbing regions (also called opaque regions) and reflective regions, patterned to define the IC pattern to be transferred to the target. In the opaque regions, an absorber is present, and the incident light is almost completely absorbed by the absorber. In the reflective regions, the absorber is removed, and the incident light is diffracted through multiple layers (multilayer reflective structures). In some implementations, the PSM is an attenuating PSM (AttPSM) or an alternating PSM (AltPSM). An exemplary PSM includes a first reflective layer (e.g., a multilayer reflective structure) and a second reflective layer patterned according to the IC pattern. In some examples, the reflectivity of an AttPSM from its absorber is 2%–15%, while the reflectivity of an AltPSM from its absorber is greater than 50%.

[0056] refer to Figure 2 , Figure 1 The EUV lithography mask 18 is described in more detail below. The EUV lithography mask 18 includes a substrate 30. In some embodiments, the substrate includes an LTM with TiO2-doped SiO2, and / or other suitable low thermal expansion materials. In some embodiments, a conductive layer 32 is also provided on the underside 42 (also referred to as the back side) of the LTM substrate 30 for electrostatic clamping purposes. In one example, the conductive layer 32 includes chromium nitride (CrN). In other embodiments, other suitable compositions are used, such as tantalum-containing materials.

[0057] The EUV lithography mask 18 includes a multilayer reflective structure 34 disposed above the side 44 (also referred to as the front) of the LTEM substrate 30. The multilayer reflective structure 34 is selected such that it provides high reflectivity for a selected radiation type / wavelength. The multilayer reflective structure 34 includes multiple film pairs, such as Mo / Si film pairs (e.g., a layer of molybdenum above or below a silicon layer in each film pair). Alternatively, the multilayer reflective structure 34 includes Mo / Be film pairs or any material with a refractive index difference that has high reflectivity at EUV wavelengths.

[0058] Now for reference Figure 3 A capping layer 35 is formed over the multilayer reflective structure 34. In some embodiments, the capping layer 35 is formed by a capping layer forming process, including epitaxial growth processes, CVD processes (e.g., APCVD, LPCVD, LECVD, or PECVD), or PVD processes (e.g., electrothermal evaporation, pulsed laser deposition, electron beam evaporation, molecular beam epitaxy, ion beam assisted evaporation, sputtering, arc evaporation, or ion beam deposition (IBD).

[0059] In some embodiments, the thickness of the capping layer 35 can be adjusted by modifying various parameters of the formation process (e.g., deposition time). In some embodiments, the thickness is adjusted to be in the range of about 1 nm to about 6 nm, for example, between about 2 nm and about 5 nm. This thickness range of the capping layer 35 helps ensure that the capping layer 35 is thick enough to adequately protect the underlying multilayer reflective structure 34, but not so thick as to significantly affect the reflectivity of the multilayer reflective structure 34. In some embodiments, the capping layer 35 has an amorphous structure, while in other embodiments, the capping layer 35 has a polycrystalline structure with a grain size of about 1 to about 5 nm. In some embodiments, the material of the capping layer 35 is selected from one or more of Ru, RuO, RuNb, RuNbO, RuZr, RuZrN, RuRh, RuON, RuNbN, RuRhN, RuVO, RuV, or RuVN.

[0060] Now for reference Figure 4A buffer layer 37 is formed above the capping layer 35. In some embodiments, the buffer layer 37 serves as an etch stop layer during the patterning or repair of the absorber layer 39 (FIG. 5) over which it is applied. In some embodiments, the purpose of the buffer layer 37 is to protect the capping layer 35 during the etching of the absorber layer 39. In some embodiments, the buffer layer 37 has different etch characteristics than the absorber layer 39. In some embodiments, the buffer layer 37 includes Ru, RuB, RuSi, RuCr, Cr, CrO, CrN, Cr2N, TaBO, TaBN, TaN, Ta2O5, TaO2, TaO, Ta2O, MoSi, MoSiN, MoSiO, SiN, SiON, SiO2, SiCON, SiC, or SiCN. In some embodiments, the thickness of the buffer layer 37 ranges from about 2 to about 20 nm.

[0061] Now for reference Figure 5 A first absorbent layer 39a is formed above the buffer layer 37. In some embodiments, the absorbent layer 39 is a double layer comprising the first absorbent layer 39a and the second absorbent layer 39b, such as... Figure 6 As shown. In some embodiments, the absorption layer 39 absorbs EUV radiation directed onto the EUV lithography mask 18. In various embodiments, the material of each absorption layer 39a and 39b comprises a pure element selected from platinum (Pt), palladium (Pd), gold (Au), iridium (Ir), osmium (Os), rhodium (Rh), ruthenium (Ru), indium (In), tellurium (Te), chromium (Cr), tungsten (W), molybdenum (Mo), tantalum (Ta), nickel (Ni), cobalt (Co), or titanium (Ti). The pure element is the principal component of each of the first absorption layer 39a and the second absorption layer 39b. In one embodiment, the first absorption layer 39a comprises the pure element Ru, and the second absorption layer 39b comprises the pure element Pt. As further explained below, in other embodiments, the first absorption layer 39a and / or the second absorption layer 39b may also comprise a dopant.

[0062] In some embodiments, the material of the first absorber layer 39a is different from the material of the second absorber layer 39b. In some embodiments, the material combinations of the first absorber layer 39a and the second absorber layer 39b include Pt + Ru, Pt + Rh, Pt + Pd, Pt + Ir, Pt + Cr, Pt + W, Pt + Mo, Pd + Ru, Pd + Rh, Pd + Ir, Pd + Cr, Pd + W, Pd + Mo, Rh + Ir, Rh + Ru, Rh + Cr, Rh + W, Rh + Mo, Ru + Ir, Ru + Cr, Ru + W, or Ru + Mo. In some embodiments, the total thickness of the absorber layer 39 is approximately 1 nm to approximately 40 nm. In some embodiments, the thickness of the first absorber layer 39a is greater than the thickness of the second absorber layer 39b. In some embodiments, the thickness of the first absorption layer 39a is approximately 15 nm to approximately 25 nm, and the thickness of the second absorption layer 39b is approximately 5 nm to approximately 15 nm. In other embodiments, the first absorption layer 39a and the second absorption layer 39b have the same thickness. In other embodiments, the thickness of the second absorption layer 39b is greater than the thickness of the first absorption layer 39a. In some embodiments, the total thickness of the absorption layers is approximately 40 nm or less to provide thinner absorption layers, thereby reducing the occurrence of masking three-dimensional effects.

[0063] In certain examples, the materials of the first absorber layer 39a and the second absorber layer 39b are capable of withstanding the harsh chemical and physical conditions during etching. In some examples, the first absorber layer 39a comprises Ru with a thickness ranging from about 14 to about 16 nm. The second absorber layer 39b comprises Pt with a thickness ranging from about 12 to about 18 nm, and the buffer layer 37 comprises CrN with a thickness ranging from about 3 nm to about 5 nm. In certain embodiments, the total thickness of the first absorber layer 39a, the second absorber layer 39b, and the buffer layer 37 is about 40 nm or less. In other embodiments, the total thickness of the first absorber layer 39a, the second absorber layer 39b, and the buffer layer 37 is in the range of about 32 nm to 37 nm.

[0064] like Figure 7As shown, in some embodiments, the absorber layer 39 includes a first absorber layer 39a, a second absorber layer 39b, and a third absorber layer 39c. In some embodiments, the materials of the first absorber layer 39a, the second absorber layer 39b, and the third absorber layer 39c are all pure elements selected from Pt, Pd, Au, Ir, Os, Rh, Ru, In, and Te. In some embodiments, the material of each absorber layer in absorber layers 39a, 39b, and 39c is different. In another embodiment, the first absorber layer 39a includes Ru with a thickness of about 5 to about 8 nm, the second absorber layer 39b includes Pt with a thickness of about 15 to about 20 nm, the third absorber layer 39c includes Ru with a thickness of about 6 to about 10 nm, and the buffer layer 37 includes CrN with a thickness of about 3 nm to about 6 nm.

[0065] In another embodiment, the first absorber layer 39a has a thickness of about 5 to about 8 nm and comprises a RuPt alloy; the second absorber layer 39b has a thickness of about 15 to about 20 nm and comprises pure elemental Pt; the third absorber layer 39c comprises pure elemental Ru and has a thickness of about 6 to about 10 nm; and the buffer layer 37 comprises CrN and has a thickness of about 3 to about 6 nm. In other embodiments, one or more of the absorber layers 39a, 39b, and 39c contain a dopant selected from one or more of O, N, B, or ON, with a concentration less than or equal to about 40 atomic percent (at%), for example, about 1 at%, about 5 at%, about 10 at%, about 20 at%, about 30 at%, or about 40 at%. In other embodiments, the dopant in one or more of the absorber layers 39a, 39b, and 39c is selected from one or more of Pt, Pd, Au, Ir, Os, Rh, Ru, In, Te, Cr, W, and Mo.

[0066] like Figure 8 As shown, due to the mixing of elemental materials during the layer formation process, one or more interdiffusion layers 41 and 43 are generated between the absorption layers 39a, 39b, and 39c. In one embodiment, the first absorption layer 39a comprises Ru with a thickness of about 5 to about 8 nm, the second absorption layer 39b comprises Pt with a thickness of about 15 to about 20 nm, the third absorption layer 39c comprises Pt with a thickness of about 6 to about 10 nm, the buffer layer 37 comprises CrN with a thickness of about 3 nm to about 6 nm, and the interdiffusion layers 41 and 43 comprise PtRu, wherein the thickness of each of the interdiffusion layers 41 and 43 is about 1 nm to about 7 nm.

[0067] In another embodiment, the first absorber layer 39a comprises a RuPt alloy with a thickness of about 5 to about 8 nm, the second absorber layer 39b comprises Pt with a thickness of about 15 to about 20 nm, the third absorber layer 39c comprises Ru with a thickness of about 6 to about 10 nm, the buffer layer 37 comprises CrN with a thickness of about 3 to about 6 nm, and the interdiffusion layers 41 and 43 are composed of PtRu with a thickness of about 1 nm to 7 nm.

[0068] In other implementation methods, such as Figure 9 As shown, four absorption layers 39a, 39b, 39c, and 39d are provided. In some embodiments, the microstructure of each of the absorption layers 39a, 39b, 39c, and 39d is polycrystalline. In other embodiments, the microstructure of each of the absorption layers 39a, 39b, 39c, and 39d is amorphous. In some embodiments, the material of the absorption layers 39d, 39c, and 39b is selected from pure elements selected from Pt, Pd, Au, Ir, Os, Rh, Ru, In, Te, Cr, W, Mo, Ta, Ni, Co, or Ti, and the absorption layer 39a comprises an alloy. In some embodiments, the alloy of the absorption layer 39a comprises RuPt. In other embodiments, a dopant is introduced into one or more of the absorption layers 39a, 39b, 39c, or 39d. The dopant is selected from one or more of O, N, B, ON, or BN, with a concentration less than or equal to about 40 atomic percent (at%), such as about 1 at%, about 5 at%, about 10 at%, about 20 at%, about 30 at%, or about 40 at%. In other embodiments, the dopant is selected from one or more of Pd, Au, Ir, Os, Rh, Ru, In, Te, Cr, W, Mo, Ta, and Ti, with a concentration less than or equal to about 1 at%, such as about 0.01 at%, about 0.05 at%, about 0.2 at%, about 0.3 at%, about 0.5 at%, or about 1 at%. In some embodiments, the total thickness of the absorption layers 39a, 39b, 39c, and 39d is less than about 40 nm. In other embodiments, one or more interdiffusion layers 41 and 43 are formed between adjacent absorption layers. Figure 8 ).

[0069] In some embodiments of this disclosure, the refractive index of the absorption layer 39 is about 0.9 or less. In some embodiments, the refractive index of the absorption layer 39 is in the range of about 0.88 to about 0.9. In other embodiments, the extinction coefficient of the absorption layer 39 is in the range of 0.02 to about 0.06. In other embodiments, the image logarithmic slope (ILS) of the absorption layer 39 is about 161.0 to about 161.3 µm. -1ILS is a measure of the contrast and resolution capabilities of a masked image, and is affected by a variety of factors, including material properties and the thickness of the absorber layer 39. In other embodiments, the normalized exposure energy (NEE) of an EUV mask ranges from about 98.3 to about 99.9 arbitrary units (AU). NEE represents the energy required to properly expose the photoresist on the wafer, relative to a standard reference. In some embodiments, an absorber layer comprising a material with a low refractive index (e.g., less than about 0.9) can produce a thinner absorber layer (e.g., less than about 40 nm), which in turn reduces the mask's three-dimensional effect, improves ILS, and lowers the exposure energy.

[0070] refer to Figure 10 A plurality of hard masks 45 are formed above the absorption layer 39. In some embodiments, a first hard mask 45a is formed above the absorption layer 39b. In some embodiments, the thickness of the first hard mask 45a is between about 2 and about 20 nm. In some embodiments, the material of the first hard mask 45a is selected from TaBO, TaBN, TaN, Ta2O5, TaO2, TaO, Ta2O, MoSi, MoSiN, MoSiO, SiN, SiON, SiO2, SiCON, SiC, SiCN, or CrN. In some embodiments, a second hard mask 45b comprises a material selected from GaN, CrON, CrCON, SiO, SiCO, Y2O3, SiCO, or SiCON. In some embodiments, the thickness of the second hard mask 45b is between about 2 and about 20 nm. In some implementations, the deposition technique for depositing the hard mask layers 45a and 45b is selected from sputtering deposition, chemical vapor deposition (CVD), plasma-enhanced CVD (PECVD), atomic layer deposition (ALD), or physical vapor deposition (PVD).

[0071] In some implementation methods, such as Figure 11As shown, three hard masks 45a, 45b, and 45c are formed, wherein the first hard mask 45a comprises a material selected from TaBN, TaN, MoSi, MoSiN, SiN, SiC, SiCN, or CrN. The second hard mask 45b comprises a material selected from TaBO, Ta2O5, TaO2, TaO, Ta2O, MoSiO, SiON, SiO2, or SiCON. The third hard mask 45c comprises a material selected from GaN, CrON, CrCON, SiO, SiCO, Y2O3, SiCO, or SiCON. The thickness of each hard mask 45a, 45b, and 45c is in the range of about 2 to about 20 nm. The capping layer 35 comprises a material selected from Ru, RuO, RuNb, RuNbO, RuZr, RuZrN, RuRh, RuON, RuNbN, RuRhN, RuVO, RuV, or RuVN, with a thickness of about 2 nm to about 5 nm. The buffer layer 37 comprises a material selected from TaBN, TaN, MoSi, MoSiN, SiN, SiC, SiCN or CrN, with a thickness of about 2 nm to about 20 nm.

[0072] In some implementation methods, such as Figure 12 As shown, four hard masks 45a, 45b, 45c, and 45d are formed, wherein the first hard mask 45a comprises a material selected from CrN or Cr2N. The second hard mask 45b comprises a material selected from TaBN, TaN, MoSi, MoSiN, SiN, SiC, SiCN, or CrN. The third hard mask 45c comprises a material selected from TaBO, Ta2O5, TaO2, TaO, Ta2O, MoSiO, SiON, SiO2, and SiCON. The fourth hard mask 45d comprises a material selected from CrON, CrCON, SiO, SiCO, Y2O3, SiCO, or SiCON. The thickness of each hard mask 45a, 45b, and 45c is in the range of about 2 to about 20 nm. The capping layer 35 comprises a material selected from Ru, RuO, RuNb, RuNbO, RuZr, RuZrN, RuRh, RuON, RuNbN, RuRhN, RuVO, RuV, or RuVN, with a thickness of approximately 2 nm to approximately 5 nm. The buffer layer 37 comprises a material selected from CrN or Cr2N, with a thickness of approximately 2 nm to approximately 20 nm. Figure 12In this embodiment, the first absorption layer 39a and the second absorption layer 39b are composed of pure elements selected from Pt, Pd, Au, Ir, Os, Rh, Ru, In, Te, Cr, W, Mo, Ta, Ni, C, or TiO2. In some embodiments, the material of the first absorption layer 39a is different from the material of the second absorption layer 39b. The thickness of each absorption layer 39a and 39b is approximately 1 to approximately 30 nm. In some embodiments, the material of each absorption layer 39a and 39b includes pure elements or elements doped with N, O, B, ON, or BN, with a doping concentration less than or equal to approximately 40 at%, for example, approximately 2 at%, approximately 5 at%, approximately 10 at%, approximately 20 at%, approximately 30 at%, or approximately 40 at%. In other implementations, the dopant is selected from one or more of Pd, Au, Ir, Os, Rh, Ru, In, Te, Cr, W, Mo, Ta, and Ti, and the concentration is less than or equal to about 1 at%, for example, about 0.01 at%, about 0.05 at%, about 0.2 at%, about 0.3 at%, about 0.5 at%, or about 1 at%. Figures 13-22 This is a cross-sectional side view of the process for fabricating a patterned photomask according to an embodiment of the present disclosure. Now refer to Figure 13 A photoresist layer 47 is formed on the uppermost hard mask layer 45d using a spin-coating process. In some examples, the photoresist layer 47 is an EUV photoresist (e.g., sensitive to radiation in the EUV range). Figure 14 As shown, the photoresist layer 47 is patterned into multiple portions 47a separated by multiple openings 49. In some embodiments, the patterning of the photoresist layer 47 includes an electron beam (E-beam) exposure process, a post-exposure baking process, and a photoresist development process.

[0073] Now for reference Figure 15 The etching process is performed using a patterned photoresist layer 47 as an etching mask. In other words, the opening 49 extends vertically through the fourth hard mask 45d until a portion of the third hard mask 45c is exposed by the opening 49. In some embodiments, the etching process includes a dry etching process. In some embodiments, such as... Figure 16 As shown, additional processing is performed to remove the patterned photoresist layer 47. In some embodiments, the photoresist removal process (not shown) includes photoresist stripping or ashing processes.

[0074] like Figure 17 As shown, additional etching is performed to pattern the hard mask 45d as an etched hard mask. In other words, the opening 49 extends vertically through the third and second hard masks 45c and 45b until a portion of the first hard mask 45a is exposed by the opening 49. Figure 18As shown, the fourth hard mask 45d is removed. In some implementations, the fourth hard mask 45d is removed by wet chemical treatment or dry chemical treatment.

[0075] like Figure 19 As shown, additional etching is performed to pattern the hard mask 45c as an etch hard mask. In other words, the opening 49 extends vertically through the second and first hard masks 45b and 45a until a portion of the second absorber layer 39b is exposed by the opening 49. Figure 20 As shown, the second and third hard masks 45b and 45c are removed. In some embodiments, the second and third hard masks 45b and 45c are removed by wet chemical treatment or dry chemical treatment.

[0076] Now for reference Figure 21 The etching process is performed using a patterned first hard mask 45a as an etching mask. In other words, the opening 49 extends vertically through the absorption layers 39a and 39b until a portion of the buffer layer 37 is exposed by the opening 49. Figure 22 As shown, additional processing is performed to remove the patterned hard mask 45a. Furthermore, in some embodiments, one or more cleaning processes may be employed to clean the patterned EUV lithography mask 18, for example, to remove contaminant particles located on the patterned EUV lithography mask 18.

[0077] Figure 23 This is a flowchart of a method for manufacturing a photolithographic mask according to various aspects of the present invention. The method includes the step of forming a multilayer reflective structure on a substrate (S2301). The method includes the step of forming a capping layer on the multilayer reflective structure (S2303). The method includes the step of forming a buffer layer over the capping layer (S2305). The method further includes the step of forming an absorption layer on the buffer layer (S2307), wherein the absorption layer includes at least a first absorption layer and a second absorption layer, each absorption layer including a non-alloying element selected from Pt, Pd, Au, Ir, Os, Rh, Ru, In, Te, Cr, W, Mo, Ta, Ni, Co, or Ti, and the first absorption layer and the second absorption layer are made of different non-alloying elements.

[0078] Figure 24This is a flowchart illustrating the fabrication of a patterned photomask according to various aspects of the present invention. The method includes the step of forming a multilayer reflective structure on a substrate (S2401). The method includes the step of forming a capping layer on the multilayer reflective structure (S2403). The method includes the step of forming a buffer layer over the capping layer (S2405). The method further includes the step of forming a plurality of absorption layers on the buffer layer (S2407), wherein the plurality of absorption layers include at least a first absorption layer and a second absorption layer, each absorption layer including a non-alloying element selected from Pt, Pd, Au, Ir, Os, Rh, Ru, In, Te, Cr, W, Mo, Ta, Ni, Co, or Ti, and the first absorption layer and the second absorption layer are made of different non-alloying elements. The method further includes the step of forming a plurality of hard masks over the plurality of absorption layers (S2409). The method includes the step of forming a photoresist layer over the plurality of hard masks (S2411). The method includes the step of performing a patterning process on the photomask to obtain a patterned photomask (S2413).

[0079] In summary, this disclosure forms a multilayer absorption layer for EUV lithography masks. Based on the above discussion, it can be seen that the material of the multilayer absorption layer in one embodiment of this disclosure has advantages over conventional EUV masks. However, it should be understood that other embodiments may offer additional advantages, and not all advantages are disclosed herein, nor is it necessary for all embodiments to have specific advantages. One advantage is that, compared to conventional EUV lithography masks, the EUV lithography mask in one embodiment of this disclosure reduces masking three-dimensional effects, including light shading, by providing a thinner absorption layer. Other advantages include the multilayer absorption layer being composed of materials that allow for easier adjustment of the refractive index and low extinction factor. Other advantages include the fact that forming a thinner absorption layer compared to conventional EUV lithography masks helps reduce exposure energy and improve the image quality of the mask.

[0080] One embodiment of this disclosure relates to a method for manufacturing a photomask. The method includes forming a multilayer reflective structure on a substrate. The method includes forming a capping layer over the multilayer reflective structure. The method includes forming a buffer layer over the capping layer. The method further includes forming an absorption layer over the buffer layer. The absorption layer includes at least a first absorption layer and a second absorption layer, each absorption layer comprising a non-alloying element selected from Pt, Pd, Au, Ir, Os, Rh, Ru, In, Te, Cr, W, Mo, Ta, Ni, Co, or Ti, and the first absorption layer and the second absorption layer are composed of different non-alloying elements.

[0081] In some embodiments, the total thickness of the absorption layer is 40 nm or less. In other embodiments, one or both of the first and second absorption layers further include a dopant selected from at least one of N, O, B, or ON. In some embodiments, the concentration of the dopant is 1 to 40 at%. In some embodiments, the absorption layer is a polycrystalline structure, while in other embodiments, the absorption layer is an amorphous structure. In some embodiments, a third absorption layer is formed above the second absorption layer, wherein the third absorption layer is made of a different material than the second absorption layer. In some embodiments, the buffer layer includes a material selected from Ru, RuB, RuSi, Cr, CrO, CrN, Cr2N, TaBO, TaBN, TaN, Ta2O5, TaO2, TaO, Ta2O, MoSi, MoSiN, MoSiO, SiN, SiON, SiO2, SiCON, SiC, or SiCN. In other embodiments, the first absorption layer includes Ru, the second absorption layer includes Pt, and the buffer layer includes CrN. In some implementation methods, a cross-diffusion layer is provided between the first absorption layer and the second absorption layer.

[0082] Another aspect of this disclosure relates to a method for manufacturing a patterned photomask. This method includes forming a multilayer reflective structure on a substrate. This method includes the step of forming a capping layer on the multilayer reflective structure. This method includes the step of forming a buffer layer over the capping layer. This method also includes forming a plurality of absorption layers over the buffer layer. The plurality of absorption layers includes at least a first absorption layer and a second absorption layer, each absorption layer containing a non-alloying element selected from Pt, Pd, Au, Ir, Os, Rh, Ru, In, Te, Cr, W, Mo, Ta, Ni, Co, or Ti. The first absorption layer and the second absorption layer are made of different non-alloying elements. This method also includes forming a plurality of hard masks over the plurality of absorption layers. This method includes forming a photoresist layer over the plurality of hard masks. This method also includes performing a patterning process on the photomask to obtain a patterned photomask.

[0083] In some embodiments, the first absorber layer comprises Ru, the second absorber layer comprises Pt, and the buffer layer comprises CrN. In other embodiments, a third absorber layer is formed above the second absorber layer, wherein the third absorber layer comprises Ru. In other embodiments, an interdiffusion layer comprising PtRu is disposed between the second and third absorber layers. In some embodiments, the thickness of the interdiffusion layer is between 1 and 5 nm. In other embodiments, the total thickness of the multiple absorber layers is 40 nm or less.

[0084] Another aspect of one embodiment disclosed herein relates to a photolithographic mask. This mask includes a substrate and a multilayer reflective structure disposed above the substrate. The mask includes a capping layer disposed above the multilayer reflective structure. Furthermore, the mask includes a buffer layer disposed above the capping layer and an absorption layer disposed above the buffer layer. The absorption layer includes at least a first absorption layer and a second absorption layer, each absorption layer comprising a non-alloying element selected from Pt, Pd, Au, Ir, Os, Rh, Ru, In, Te, Cr, W, Mo, Ta, Ni, Co, or Ti. The first absorption layer and the second absorption layer are made of different non-alloying elements.

[0085] In some embodiments, one or both of the first and second absorber layers also include a dopant selected from at least one of N, O, B, or ON. In some embodiments, an interdiffusion layer is provided between the first and second absorber layers. In other embodiments, the buffer layer includes a material selected from Ru, RuB, RuSi, Cr, CrO, CrN, Cr2N, TaBO, TaBN, TaN, Ta2O5, TaO2, TaO, Ta2O, MoSi, MoSiN, MoSiO, SiN, SiON, SiO2, SiCON, SiC, or SiCN.

[0086] The features of many embodiments have been outlined above to enable those skilled in the art to better understand the following detailed description. Those skilled in the art should understand that they can readily use this disclosure as a basis to design or modify other processes and structures to achieve the same objectives and / or advantages as the embodiments described herein. Those skilled in the art should also recognize that such equivalent constructions do not depart from the spirit and scope of one embodiment of this disclosure, and that various changes, substitutions, and modifications can be made without departing from the spirit and scope of one embodiment of this disclosure.

Claims

1. A method for manufacturing a photolithographic mask, characterized in that, include: A multilayer reflective structure is formed on a substrate; A capping layer is formed on top of the multi-layered reflective structure; A buffer layer is formed on top of the cover layer; and An absorbent layer is formed on top of the buffer layer; The absorber layer includes at least one first absorber layer and one second absorber layer, each including a non-alloy component selected from platinum, palladium, gold, iridium, osmium, rhodium, ruthenium, indium, tellurium, chromium, tungsten, molybdenum, tantalum, nickel, cobalt, or titanium. The first absorbent layer and the second absorbent layer are made of different non-alloy components.

2. The method for manufacturing a photolithographic mask as described in claim 1, characterized in that, The total thickness of the absorption layer is less than or equal to 40 nanometers.

3. The method for manufacturing a photolithographic mask as described in claim 1, characterized in that, One or both of the first absorption layer and the second absorption layer further include a dopant selected from at least one of nitrogen, oxygen, boron, or oxynitride.

4. The method for manufacturing a photolithographic mask as described in claim 3, characterized in that, The concentration of this dopant is between 1 and 40 atomic percent.

5. The method for manufacturing a photolithographic mask as described in claim 1, characterized in that, The absorption layer has a polycrystalline structure.

6. The method for manufacturing a photolithographic mask as described in claim 1, characterized in that, Also includes: A third absorbent layer is formed on top of the second absorbent layer, wherein the third absorbent layer is made of a different material than the second absorbent layer.

7. The method for manufacturing a photolithographic mask as described in claim 1, characterized in that, An interdiffusion layer is disposed between the first absorption layer and the second absorption layer.

8. A method for manufacturing a photolithographic mask, characterized in that, include: A multilayer reflective structure is formed on a substrate; A capping layer is formed on top of the multi-layered reflective structure; A buffer layer is formed on top of the cover layer; Multiple absorption layers are formed on the buffer layer, said multiple absorption layers including at least one first absorption layer and one second absorption layer, each including a non-alloy component selected from platinum, palladium, gold, iridium, osmium, rhodium, ruthenium, indium, tellurium, chromium, tungsten, molybdenum, tantalum, nickel, cobalt or titanium. The first absorbent layer and the second absorbent layer are made of different non-alloy components; Multiple hard shields are formed on the multiple absorption layers; A photoresist layer is formed on the multiple hard masks; as well as A patterning process is performed on the photomask to obtain a patterned photomask.

9. A photolithography mask, characterized in that, include: One substrate; A multi-layer reflective structure is disposed on the substrate; A cover layer is placed on top of the multi-layered reflective structure; A buffer layer is disposed on top of the cover layer; and An absorbent layer is placed on top of the buffer layer. The absorber layer includes at least one first absorber layer and one second absorber layer, each including a non-alloy component selected from platinum, palladium, gold, iridium, osmium, rhodium, ruthenium, indium, tellurium, chromium, tungsten, molybdenum, tantalum, nickel, cobalt, or titanium. The first absorption layer and the second absorption layer are made of different non-alloy components.

10. The photolithography mask as described in claim 9, characterized in that, One or both of the first absorption layer and the second absorption layer further include a dopant selected from at least one of nitrogen, oxygen, boron, oxynitride or boron nitride.

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