Photoresists used in semiconductor manufacturing

Abstract

The present application relates to photoresists for semiconductor manufacturing. An organometallic precursor for extreme ultraviolet (EUV) lithography is provided. The organometallic precursor comprises an aromatic bidentate ligand, a transition metal coordinated to the aromatic bidentate ligand, and an extreme ultraviolet (EUV) cleavable ligand coordinated to the transition metal. The aromatic bidentate ligand comprises a plurality of pyrazine molecules.

Description

[0001] Priority data

[0002] This application claims priority to U.S. Provisional Patent Application Serial No. 63 / 085,305, filed on September 30, 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The present application relates to photoresists used in semiconductor manufacturing. Background Art

[0004] The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced generations of ICs, each with smaller, more complex circuits than the previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased, while geometry size (i.e., the smallest component (or line) that can be produced using a manufacturing process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and reducing associated costs. This scaling down also increases the complexity of processing and manufacturing ICs, and similar developments in IC processing and manufacturing are needed to achieve these advances.

[0005] In one exemplary aspect, photolithography is a process for selectively removing a portion of a material layer in semiconductor microfabrication. The process uses a radiation source to transfer a pattern (e.g., a geometric pattern) from a photomask to a photosensitive layer (e.g., a photoresist layer) on the material layer. The radiation causes a chemical change (e.g., an increase or decrease in solubility) in the exposed area of ​​the photosensitive layer. A baking process can be performed before and / or after exposure, such as in a baking process before and / or after exposure. Then, a developing process selectively removes exposed or unexposed areas with a developer solution to form an exposed pattern in the material layer. In order to improve the resolution of the photolithography process to accommodate IC devices with high functional density, a radiation source with a shorter wavelength has emerged. One of them is an extreme ultraviolet (EUV) radiation source. Although existing EUV photoresists are generally sufficient for their intended purpose, they are not completely satisfactory. Other improvements are desired. Summary of the invention

[0006] In some embodiments of the present invention, an organometallic precursor is provided, the organometallic precursor comprising: an aromatic bidentate ligand; a transition metal coordinated to the aromatic bidentate ligand; and an extreme ultraviolet (EUV) cleavable ligand coordinated to the transition metal, wherein the aromatic bidentate ligand comprises a plurality of pyrazine molecules.

[0007] In other embodiments of the present invention, an extreme ultraviolet (EUV) photoresist precursor is provided, which comprises: an aromatic bidentate ligand, wherein the aromatic bidentate ligand comprises a first pyrazine ring and a second pyrazine ring; a transition metal coordinated to the nitrogen atom on the first pyrazine ring and the nitrogen atom on the second pyrazine ring; a first EUV cleavable ligand coordinated to the transition metal; and a second EUV cleavable ligand coordinated to the transition metal.

[0008] In still other embodiments of the present invention, a method for depositing a photoresist layer is provided, the method comprising: depositing a photoresist layer directly on a material layer, wherein the photoresist layer comprises a precursor, the precursor comprising: an aromatic bidentate ligand, the aromatic bidentate ligand comprising a first pyrazine ring and a second pyrazine ring, the first pyrazine ring comprising a first nitrogen atom and a second nitrogen atom, the second pyrazine ring comprising a first nitrogen atom and a second nitrogen atom, a transition metal coordinated to the first nitrogen atom on the first pyrazine ring and the first nitrogen atom on the second pyrazine ring, and a first EUV cleavable ligand and a second EUV cleavable ligand coordinated to the transition metal; and exposing a portion of the photoresist layer to EUV radiation to: cleave the first EUV cleavable ligand and the second EUV cleavable ligand from the transition metal, and activate the second nitrogen atom on the first pyrazine ring and the second nitrogen atom on the second pyrazine ring. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present disclosure can be best understood from the following detailed description when read in conjunction with the accompanying drawings. It is emphasized that, in accordance with standard practice in the industry, various features are not drawn to scale and are used for illustration purposes only. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity.

[0010] Figure 1 The molecular structure of the organometallic precursor according to various aspects of the present disclosure is schematically shown.

[0011] Figure 2 and Figure 3 Schematically illustrating changes in coordination of organometallic precursor molecules due to incident EUV radiation according to various aspects of the present disclosure.

[0012] Figure 4 Schematically illustrating ordered cross-linking of organometallic precursor molecules according to various aspects of the present disclosure.

[0013] Figure 5 A flow chart of a method 200 for patterning a workpiece according to various aspects of the present disclosure is shown.

[0014] Figure 6-11 Showing the experience according to various aspects of the present disclosure Figure 5 A partial cross-sectional view of a workpiece during various steps of method 200 . DETAILED DESCRIPTION

[0015] The following disclosure provides many different embodiments or examples for realizing the different characteristic features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. Of course, these are merely examples and are not intended to be limiting. For example, in the following description, the formation of a first feature above or on a second feature may include an embodiment in which the first and second features are directly contacted and formed, and may also include an embodiment in which additional features are formed between the first and second features so that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numbers and / or letters in various examples. This repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between the various embodiments and / or arrangements discussed.

[0016] For ease of description, spatially relative terms, such as "below", "beneath", "below", "above", etc., may be used herein to describe the relationship of one element or feature to another element or feature as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein should likewise be interpreted accordingly.

[0017] In addition, when "about," "approximately," or the like is used to describe a number or a range of numbers, the term is intended to encompass numbers within a reasonable range, taking into account variations that inherently occur during manufacturing, as understood by one of ordinary skill in the art. For example, based on known manufacturing tolerances associated with manufacturing features having properties associated with the number, a number or range of numbers encompasses a reasonable range that includes the described number, such as within + / -10% of the described number. For example, a layer of material having a thickness of "about 5 nm" may include a range of dimensions of 4.25 nm to 5.75 nm, where the manufacturing tolerance associated with depositing material layers is known to one of ordinary skill in the art to be + / -15%. Further, the present disclosure may repeat reference numbers and / or letters in various examples. This repetition is for the purposes of simplicity and clarity and does not, by itself, indicate a relationship between the various embodiments and / or configurations discussed.

[0018] The present disclosure relates generally to EUV lithography and, more particularly, to organometallic precursors in EUV photoresists.

[0019] Some existing EUV photoresists are in the form of solutions including cationic species and anionic species. The anionic species include metal ions coordinated with EUV stable ligands and bridge ligands. The bridge ligand is used as a crosslinker to coordinate with another metal ion. Exemplary bridge ligands in some existing EUV can include oxalate ions (C 2 O 4 2- ). Such EUV photoresists have poor adhesion to various surfaces. In order to improve adhesion, surface treatment or adhesion promoting layer is required to ensure satisfactory adhesion. Examples of adhesion promoting layers may include hexamethyldisilazane (HMDS). In addition, since the bridge ligands are both EUV cleavable and cross-linking agents, it is difficult to control the EUV-induced cross-linking process well. On the one hand, some bridge ligands need to be cleaved from metal ions to produce non-coordinated cross-linking sites. On the other hand, some bridge ligands need to remain coordinated with metal ions to act as cross-linking agents. When no bridge ligands are cleaved or all bridge ligands are cleaved, cross-linking may not be satisfactory. Moreover, due to the lack of structural matching, existing EUV photoresist layers may have a gradient of cross-linking along their depth. In some examples, the degree of cross-linking near the top surface is higher, while the degree of cross-linking away from the top surface is lower. Such a cross-linking gradient may cause scum defects, poor line edge roughness (LER), and low lithography contrast after development.

[0020] The present disclosure provides an organometallic precursor in a photoresist, comprising an aromatic bidentate ligand having a structural match for intermolecular coordination. In one embodiment of the present disclosure, the organometallic precursor comprises a 2,2'-bipyrazine molecule coordinated to a transition metal with high EUV absorption. The transition metal is also coordinated to EUV cleavable ligands, which may be cleaved by EUV radiation to form uncoordinated sites. When the aromatic bidentate ligand is an aromatic 2,2'-bipyrazine, two nitrogen atoms in the opposite side may be coordinated to non-coordinated sites. The structural match of intermolecular coordination and the π-π interaction of the aromatic ligands can lead to an ordered stacking of layers. The ordered stacking produces a crystalline polymer structure, resulting in reduced defects (reduced scum), good LER and high contrast.

[0021] The aromatic bidentate ligands of the present disclosure meet several criteria. First, as the name implies, the aromatic bidentate ligand contains at least one aromatic ring to provide a conjugated system and allow π-π stacking. Second, the aromatic bidentate ligand contains a dentition equal to 2. That is, the aromatic bidentate ligand contains two atoms that can bind to the central metal ion in the coordination complex. It is not insignificant that the aromatic bidentate ligand is bidentate. Transition metal complexes are characterized by a coordination number ranging from 1 to 12, but the most common coordination numbers are 2, 4 and 6. For metals with high atomic absorption cross sections, such as those described in the present disclosure, the coordination number is greater than 4 and is likely to be 6. If the metal must be coordinated with two organometallic precursor molecules and still maintain unsaturated sites to improve adhesion, each organometallic precursor can only be monodentate or bidentate. Since monodentate is less conducive to ordered structures, bidentate is selected. Third, the aromatic bidentate ligand contains a symmetrical structure for ordered cross-linking. Fourth, in addition to atoms providing toothing, the aromatic bidentate ligand also includes EUV activated ligands that can be used for crosslinking. Fifth, the aromatic bidentate ligand may optionally include a planar structure to promote π-π stacking, which is conducive to ordered interlayer interactions. Examples may include 2,2'-bipyrazine (C 8 H 6 N 4 )、2,2'-bipyrimidine (C 8 H 6 N 4 )、3,3'-bipyridine (C 8 H 6 N 4 ), each comprising two linked heterocyclic aromatic rings.

[0022] Figure 1 Schematic molecular structure of an organometallic precursor molecule 100 according to various aspects of the present disclosure is shown. The organometallic precursor molecule 100 includes an aromatic bidentate ligand (X) 102, an aromatic metal ion (M) 104 coordinated to the aromatic bidentate ligand 102, and a plurality of EUV cleavable ligands (R) 106 coordinated to the metal ion 104. In the embodiment shown, the aromatic bidentate ligand 102 is an aromatic 2,2'-bipyrazine. It should be understood that similar descriptions can apply to other embodiments of the aromatic bidentate ligand 102. The organometallic precursor molecule 100 can also be represented as M a X b R c, where M represents a metal ion 104, R represents an EUV cleavable ligand 106, X represents an aromatic bidentate ligand 102, "a" is 1, "b" is 1 and "c" is 2. The metal ion 104 may include a metal having a high atomic absorption cross section. Examples of the metal ion 104 may include tin (Sn), bismuth (Bi), antimony (Sb), indium (In) or tellurium (Te). Since the metal ion 104 may have six (6) coordination sites, the total number of EUV cleavable ligands (R) 106 and aromatic bidentate ligands (X) 102 does not occupy all coordination sites, leaving up to two unsaturated sites (i.e., uncoordinated sites) to improve adhesion. Unlike some existing organometallic precursors that are in ionic form and stabilized by counterions, the organometallic precursor molecule 100 is charge neutral. In some embodiments, the organometallic precursor molecule 100 of the present disclosure may be prepared ex situ and then deposited on a semiconductor device workpiece using a spin coating method. In some other embodiments, the organometallic precursor molecules 100 may be deposited on a semiconductor device workpiece using chemical vapor deposition (CVD) or atomic layer deposition (ALD).

[0023] In the illustrated embodiment, the aromatic bidentate ligand 102 may be 2,2'-bipyrazine, which includes two pyrazine rings connected together at position 2 of the first pyrazine ring and position 2' of the second pyrazine ring. The two pyrazine rings may be referred to as the first pyrazine ring and the second pyrazine ring. The first pyrazine ring comprises nitrogen atoms at positions 1 and 4. The second pyrazine ring comprises nitrogen atoms at positions 1' and 4'. 2,2'-bipyrazine is coordinated with the metal ion 104 by the nitrogen atoms at positions 1 of the first pyrazine ring and at positions 1' of the second pyrazine ring. The metal ion 104 is further coordinated with two EUV cleavable ligands 106. The nitrogen atoms at positions 4 of the first pyrazine ring and at positions 4' of the second pyrazine ring may be activated by EUV radiation. As will be described below, once activated, they may coordinate with the metal ion 104, thereby cleaving one or more EUV cleavable ligands 106. The EUV cleavable ligand 106 may include an alkenyl group or a carboxylate group. The alkenyl group or the carboxylate group may include hydrogen, fluorine or an alkyl group. When present, the alkyl group in the EUV cleavable ligand 106 can be linear, branched or cyclic and can contain 1 to 6 carbon atoms. Both the alkenyl and carboxylate groups contain double bonds, which can be cut by the occurrence of EUV radiation, giving these EUV cleavable ligands their EUV cleavable properties. Due to the π conjugated system in each pyrazine ring, the pyrazine ring is planar. In fact, 2,2'-bipyrazine can be in a cross-plane configuration. In this way, the organometallic precursor molecule 100 can be symmetrical about the bond between position 2 of the first pyrazine ring and position 2' of the second pyrazine ring.

[0024] Figure 2 and Figure 3Schematically illustrates the change in coordination of an organometallic precursor molecule 100 due to the incidence of EUV radiation. Figure 2 and 3 Three organometallic precursor molecules 100 are shown. Figure 2 , the incidence of EUV can generate free radicals, which can cleave from the EUV cleavable ligand 106, generate empty coordination sites on the metal ion 104, and can activate the nitrogen atom at position 4 or position 4'. Figure 2 As shown, the activated nitrogen atom is available to coordinate with a vacant coordination site (shown as a circle for ease of illustration) on the metal ion 104 of other organometallic precursor molecules 100. Figure 3 , during the post-exposure bake process after EUV exposure, the activated nitrogen atom at position 4 or 4 ′ can coordinate with an available coordination site on the metal ion 104 of another organometallic precursor molecule 100 .

[0025] Due to the cross-plane configuration of the organometallic precursor molecules 100, cross-linking between the organometallic precursor molecules 100 can occur in a layer on the molecular plane. Figure 4 The ordered cross-linking of the organometallic precursor molecules 100 in such a layer is shown. For each organometallic precursor molecule 100, EUV exposure can cleave the EUV cleavable ligand 106 from the metal ion 104 and activate the nitrogen atoms at position 4 and position 4'. During the post-exposure bake process, the activated nitrogen atom at position 4 (or position -4') coordinates with the available site on the metal ion 104. Figure 4 As shown, the metal ion 104 of the organometallic precursor molecule 100 can coordinate with two positions 4 (or position 4') of two other organometallic precursor molecules 100, thereby cross-linking them together. At the same time, the nitrogen atoms at positions 4 and 4' of the same organometallic precursor molecule 100 coordinate with two metal ions 104 of the other two organometallic precursor molecules. In the case where each metal ion 104 coordinates with four nitrogen atoms at positions 4 (or positions 4'), the cross-linked organometallic precursor molecule 100 can have good short-range and long-range order in each layer. Between different layers (or molecular planes), the π stacking (or pi stacking or π-π stacking) between aromatic pyrazine rings controls non-covalent interlayer interactions. π stacking helps to establish orderly stacking between different layers (or molecular planes). Due to the symmetrical structure of the organometallic precursor molecule 100 and the π stacking between the aromatic pyrazine rings, the organometallic precursor molecule 100 of the present disclosure can lead to a crystalline polymer structure, which can provide uniform cross-linking, reduce defects, reduce scum, improve LER, and promote high development contrast.

[0026] In general, a positive photoresist (positive photoresist or positive tone photoresist) is a type of photoresist in which the portion of the photoresist exposed to light becomes soluble in a photoresist developer. The unexposed portion of the photoresist remains insoluble in the photoresist developer. A negative photoresist (negative photoresist or negative tone photoresist) is a type of photoresist in which the portion of the photoresist exposed to light becomes insoluble in a photoresist developer. The unexposed portion of the photoresist is dissolved by the photoresist developer. Because EUV radiation forms crosslinks to reduce the solubility of the organometallic precursor molecule 100 in the developer, the organometallic precursor molecule 100 of the present disclosure can be an active ingredient in a negative photoresist for EUV lithography. Figure 5 A flow chart of a method 200 for patterning a material layer on a workpiece using a negative photoresist including an organometallic precursor molecule 100 as described herein is shown. The method 200 is merely an example and is not intended to limit the present disclosure to what is explicitly shown in the method 200. Other steps may be provided before, during, and after the method 200, and certain steps described may be replaced, eliminated, or moved for other embodiments of the method. For simplicity, not all steps are described in detail herein. Figure 6-11 Describing method 200, Figure 6-11 is a partial cross-sectional view of a workpiece 300 at various stages of fabrication according to an embodiment of the method 200. Additionally, throughout this application, like reference numerals refer to like features unless otherwise noted.

[0027] refer to Figure 5 and 6 , the method 200 includes a frame 202, wherein a workpiece 300 is provided. The workpiece 300 includes a substrate 301 and a material layer 302 disposed above the substrate 301. It should be noted that the substrate 301 is Figure 6 In order to simplify the Figure 7-11The substrate 301 may include a single element semiconductor, such as silicon (Si) and / or germanium (Ge); a compound semiconductor, such as silicon carbide (SiC), gallium arsenide (GaAs), gallium phosphide (GaP), indium phosphide (InP), indium arsenide (InAs), and / or indium antimonide (InSb); an alloy semiconductor, such as silicon germanium (SiGe), gallium arsenic phosphide (GaAsP), aluminum indium arsenide (AlInAs), aluminum gallium arsenide (AlGaAs), gallium indium arsenide (GaInAs), gallium indium phosphide (GaInP), and / or gallium indium arsenide phosphide (GaInAsP); a non-semiconductor material, such as soda lime glass, fused silica, fused quartz, and / or calcium fluoride (CaF 2 ); and / or combinations thereof. In some other embodiments, substrate 301 may be a single layer of material having a uniform composition; alternatively, substrate 301 may include multiple material layers having similar or different compositions suitable for IC device fabrication. In one example, substrate 301 may be a silicon-on-insulator (SOI) substrate having a semiconductor silicon layer formed on a silicon oxide layer. Substrate 301 may include various circuit features formed thereon, including, for example, field effect transistors (FETs), metal oxide semiconductor field effect transistors (MOSFETs), CMOS transistors, high voltage transistors, high frequency transistors, bipolar junction transistors, diodes, resistors, capacitors, inductors, varactors, other suitable devices, and / or combinations thereof.

[0028] The material layer 302 above the substrate 301 represents the uppermost layer on which a photoresist layer 304 (described below) will be deposited. In some embodiments, the material layer 302 can be a dielectric layer used as a hard mask layer, a bottom anti-reflective coating (BARC), or an insulating layer. In these embodiments, the material layer 302 can include silicon oxide, silicon nitride, silicon oxynitride, silicon nitride carbon, silicon nitride carbon oxide, metal oxide, silicon carbide, or silicon oxycarbide. Exemplary metal oxides can include high-k dielectric materials such as titanium oxide (TiO 2 ), hafnium zirconium oxide (HfZrO), tantalum oxide (Ta 2 O 5 ), Hafnium Silicon Oxide (HfSiO 4 ), zirconium oxide (ZrO 2 ), zirconium oxide silicon (ZrSiO 2 ), lanthanum oxide (La 2 O 3 ), aluminum oxide (Al 2 O 3 )、ZrO、Yttrium oxide (Y 2 O 3 )、SrTiO 3 (STO), BaTiO 3(BTO), BaZrO, Hafnium Lanthanum Oxide (HfLaO), Lanthanum Silicon Oxide (LaSiO), Aluminum Silicon Oxide (AlSiO), Hafnium Tantalum Oxide (HfTaO), Hafnium Titanium Oxide (HfTiO), or (Ba,Sr)TiO 3 (BST). In some other embodiments, the material layer 302 may include a semiconductor material such as silicon (Si), germanium (Ge), gallium arsenide (GaAs), gallium phosphide (GaP), gallium nitride (GaN), or silicon germanium (SiGe). In other embodiments, the material layer 302 may include a polymer layer, such as a polyimide layer or a polymer BARC layer. In other embodiments, the material layer 302 may include a conductive material, such as titanium nitride (TiN), titanium aluminum (TiAl), titanium aluminum nitride (TiAlN), tantalum nitride (TaN), tantalum aluminum (TaAl), tantalum aluminum nitride (TaAlN), tantalum aluminum carbide (TaAlC), tantalum carbonitride (TaCN), aluminum (Al), tungsten (W), nickel (Ni), titanium (Ti), ruthenium (Ru), cobalt (Co), platinum (Pt), tantalum carbide (TaC), tantalum silicon nitride (TaSiN), or copper (Cu). When the material layer 302 includes surface functional groups such as hydroxyl or amine groups, the material layer 302 can form good adhesion with the subsequently deposited photoresist layer 304 because the photoresist layer 304 includes the organometallic precursor molecules 100, which include uncoordinated sites for adhesion. In some embodiments (described below) where the material layer 302 can catalyze premature crosslinking of the photoresist layer 304, at block 202, a very thin silicon oxide layer or a very thin polymer layer can be deposited on the material layer 302 before depositing the photoresist layer.

[0029] refer to Figure 5 and Figure 6, method 200 includes frame 204, wherein a photoresist layer 304 is deposited on the material layer 302. The photoresist layer 304 includes the above-mentioned organometallic precursor molecules 100, and may include other additives or surfactants. The photoresist layer 304 may be a negative photoresist layer. In some embodiments, the photoresist layer 304 may be deposited using spin coating, CVD, or atomic layer deposition (ALD). When the photoresist layer 304 is deposited using spin coating, the organometallic precursor molecules 100 may be dissolved or dispersed in a dispersion or solution together with additives and surfactants, and then coated on the material layer 302. In some cases, the solution of the coating of the photoresist layer 304 may also include other cross-linkable polymers, such as poly (2-hydroxyethyl methacrylate) (pHEMA), poly (4-hydroxystyrene) (PHS), polyglycidyl ether, or polyether polyol. The inclusion of these other cross-linkable polymers may enhance the cross-linking reaction after EUV exposure. When the photoresist layer 304 is deposited using ALD or CVD, the gas precursor of the organic metal precursor molecule 100 can be directed to the material layer 302, where the gas precursors react with each other and with the material layer 302 to form the photoresist layer 304. In some cases, the gas precursor may include a first gas precursor and a second gas precursor. The first gas precursor may include a halogenated EUV cleavable ligand, such as a halogenated olefin. The second gas precursor may include a metal ion 104 coordinated with an aromatic bidentate ligand 102 and a halide. The halogen component allows the gas precursor to be in a gaseous form. During the CVD or ALD process, the material layer 302 may be heated, and when the first and second gas precursors contact the heated material layer 302, the halogen component may be removed, thereby forming the organic metal precursor molecule 100 in the photoresist layer 304.

[0030] refer to Figure 5 and 7 , method 200 includes box 206, in which a pre-exposure treatment process 400 is performed. The pre-exposure treatment process 400 may also be referred to as a post-application treatment process 400. The pre-exposure treatment process 400 promotes the degassing of undesirable substances or removes excess moisture in the photoresist layer 304. Undesirable substances may include leaving groups or byproducts during the CVD or ALD process when the photoresist layer 304 is deposited using a gaseous precursor. Examples may include halide-containing substances. Depending on the nature of the substance to be removed, the pre-exposure treatment process 400 may include a baking process, an infrared curing process, an ultraviolet (UV) curing process, or a visible light curing process. In some alternative embodiments in which the undesirable substances are to be neutralized, the pre-exposure treatment process may include using a silane (SiH 4) to modify the surface of the photoresist layer 304. When the pre-exposure treatment process 400 includes a baking process, the baking temperature may be between about 60°C and about 170°C.

[0031] refer to Figure 5 and 8 , method 200 includes block 208, wherein the photoresist layer 304 is exposed to a radiation pattern. Figure 8 The exposure at block 208 is performed using a lithography system 500 schematically shown in FIG. 5 . The lithography system 500 may also be generally referred to as a scanner, which is operable to perform a lithography process, including exposure with a corresponding radiation source and in a specific exposure mode. In at least some embodiments of the present invention, the lithography system 500 includes an extreme ultraviolet (EUV) lithography system that is designed to expose a photoresist layer such as the photoresist layer 304 by EUV radiation. Figure 8 The lithography system 500 includes a plurality of subsystems, such as an EUV source 502, an illuminator 504, a mask stage 506 configured to receive a mask 508, a projection optics 510, and a substrate stage 514 configured to receive a workpiece, such as the workpiece 300. A general description of the operation of the lithography system 500 can be given as follows: EUV radiation from the EUV source 502 is directed toward the illuminator 504 (which includes a set of mirrors) and projected onto the reflective mask 508. The reflected mask image is directed toward the projection optics 510, which focuses the EUV light and projects the EUV light onto the workpiece 300 to expose the EUV resist layer deposited thereon. Additionally, in various examples, each subsystem of the lithography system 500 can be housed in and thus operated within a high vacuum environment, such as to reduce atmospheric absorption of the EUV light.

[0032] In embodiments described herein, the EUV source 502 may be used to generate EUV radiation. In some embodiments, the EUV source 502 includes a plasma source, such as a discharge producing plasma (DPP) or a laser producing plasma (LPP). In some embodiments, the EUV radiation may include radiation having a wavelength centered at approximately 13.5 nm. In some embodiments, the EUV source 502 also includes a collector that may be used to collect EUV radiation generated from the plasma source and direct the EUV radiation toward imaging optics such as an illuminator 504. As described above, the EUV radiation from the EUV source 502 is directed toward the illuminator 504. In some embodiments, the illuminator 504 may include reflective optics, such as a single mirror or a mirror system having a plurality of mirrors, to direct radiation from the EUV source 502 onto a mask stage 506, and in particular, onto a mask 508 fixed to the mask stage 506. In some examples, the illuminator 504 may include a zone plate, for example, to improve the focusing of the EUV radiation. In some embodiments, the illuminator 504 can be configured to shape the EUV radiation passing therethrough according to a particular pupil shape and including, for example, a dipole shape, a quadrupole shape, a toroidal shape, a single beam shape, a multi-beam shape, and / or a combination thereof. In some embodiments, the illuminator 504 is operable to configure a reflector (i.e., of the illuminator 504) to provide desired illumination to the mask 508. In one example, the reflector of the illuminator 504 can be configured to reflect the EUV radiation to different illumination positions. In some embodiments, the platform before the illuminator 504 can additionally include other configurable reflectors that can be used to direct the EUV radiation to different illumination positions within the reflector of the illuminator 504. In some embodiments, the illuminator 504 is configured to provide on-axis illumination (ONI) to the mask 508. In some embodiments, the illuminator 504 is configured to provide off-axis illumination (OAI) to the mask 508. It should be noted that the optics employed in EUV lithography system 500, particularly for illuminator 504 and projection optics 510, may include mirrors with multi-layer thin film coatings, known as Bragg reflectors. For example, such multi-layer thin film coatings may include alternating layers of Mo and Si, which provide high reflectivity at EUV wavelengths (e.g., about 13 nm).

[0033] As described above, the lithography system 500 also includes a mask stage 506 configured to hold a mask 508. Since the lithography system 500 can be housed in a high vacuum environment and thus operated therein, the mask stage 506 can include an electrostatic chuck (e-chuck) to hold the mask 508. Like the optical devices of the EUV lithography system 500, the mask 508 is also reflective. Figure 8As shown in the example of , radiation reflects from the mask 508 and is directed to the projection optics 510, which collects the EUV radiation reflected from the mask 508. For example, the EUV radiation (reflected from the mask 508) collected by the projection optics 510 carries an image of the pattern defined by the mask 508. In various embodiments, the projection optics 510 is used to image the pattern of the mask 508 onto the workpiece 300 fixed on the substrate stage 514 of the lithography system 500. In particular, in various embodiments, the projection optics 510 focuses the collected EUV light and projects the EUV light onto the workpiece 300 to expose the photoresist layer 304 on the workpiece 300. As described above, the projection optics 510 may include reflective optics, such as used in an EUV lithography system such as the lithography system 500. In some embodiments, the illuminator 504 and the projection optics 510 are collectively referred to as an optical module of the lithography system 500.

[0034] In some embodiments, the lithography system 500 further includes a pupil phase modulator 512 to modulate the optical phase of EUV radiation directed from the mask 508 so that the light has a phase distribution along a projection pupil plane. In some embodiments, the pupil phase modulator 512 includes a mechanism to adjust a mirror of the projection optics 510 for phase modulation. For example, in some embodiments, the mirror of the projection optics 510 can be configured to reflect EUV light through the pupil phase modulator 512, thereby modulating the phase of the light passing through the projection optics 510. In some embodiments, the pupil phase modulator 512 utilizes a pupil filter placed on the projection pupil plane. For example, a pupil filter can be used to filter out specific spatial frequency components of EUV radiation reflected from the mask 508. In some embodiments, the pupil filter can be used as a phase pupil filter to modulate the phase distribution of light directed through the projection optics 510.

[0035] like Figure 8 As shown, using the photolithography system 500, the exposed portions 310 of the photoresist layer 304 are exposed to EUV radiation, while the unexposed portions 308 remain unexposed. The organometallic precursor molecules 100 in the exposed portions 310 of the photoresist layer 304 become cross-linked. More specifically, referring to Figure 1 and Figure 2 , EUV radiation from the lithography system 500 generates free radicals. The free radicals cause the EUV cleavable ligand 106 to cleave from the metal ion 104. The nitrogen atom at position 4 or position 4' is activated and coordinates to another metal ion with an uncoordinated site. The aromatic bidentate ligand 102 acts as a bridge ligand to form a crosslink. Due to the lack of free radicals, the same crosslinking does not occur in the unexposed portion 308. As described above with respect to Figure 4As described above, due to the cross-plane configuration of the organometallic precursor molecules 100, cross-linking between the organometallic precursor molecules 100 can occur in the layer on the molecular plane. For each organometallic precursor molecule 100 in the photoresist layer 304, EUV exposure can cleave the EUV cleavable ligand 106 from the metal ion 104 and activate the nitrogen atoms at positions 4 and 4' of the aromatic bidentate ligand 102.

[0036] refer to Figure 5 and 9 , the method 200 includes a block 210, in which a post-exposure bake process 600 is performed. In some embodiments, the bake temperature or bake temperature profile of the post-exposure bake process 600 is selected to promote crosslinking and ensure the removal of the leaving groups generated during the EUV exposure process at block 208. The bake temperature of the post-exposure bake process 600 can be between about 150° C. and about 300° C. During the post-exposure bake process 600, the activated position 4 (or position 4') nitrogen atom of the organic metal precursor molecule 100 in the exposed portion 310 is coordinated with the available sites on the metal ion 104 of the two adjacent organic metal precursor molecules 100. The metal ion 104 of the same organic metal precursor molecule 100 can be coordinated with two position 4 (or position 4') nitrogen atoms of two other organic metal precursor molecules 100, thereby crosslinking them together. With each metal ion 104 coordinated to four position 4 (or position 4') nitrogen atoms, the crosslinked organic metal precursor molecules 100 can have good short-range and long-range order in each layer. Between different layers (or molecular planes), the π stacking (or pi stacking or π-π stacking) between the aromatic pyrazine rings controls the non-covalent interlayer interactions. π stacking helps to establish an ordered stacking between different layers (or molecular planes). Due to the symmetrical structure of the organometallic precursor molecule 100 and the π stacking between the aromatic pyrazine rings, the organometallic precursor molecule 100 of the present disclosure can lead to a crystalline polymer structure, which can provide uniform cross-linking, reduce defects, reduce scum, improve LER, and promote high development contrast. The leaving group removed at box 210 can include an EUV cleavable ligand 106, a halide-containing substance, or a combination thereof.

[0037] refer to Figure 5 and 10, method 200 includes frame 212, wherein the exposed photoresist layer 304 is developed to form a patterned photoresist layer 312. At frame 212, a developer solution is used to remove the unexposed portion 308, which is not cross-linked at frame 208. The developer solution is selected so that it is suitable for selectively dissolving and removing the unexposed portion 308 (not cross-linked), while the exposed portion 310 (cross-linked) of the photoresist layer 304 remains substantially intact. Suitable developer solutions may include solvents such as n-butyl acetate, ethanol, hexane, benzene, toluene, water, isopropyl alcohol (IPA) or 2-heptanone. In some embodiments, frame 212 may also include one or more descum or rinse processes to remove any residual photoresist layer 304 or debris. At the end of the operation at frame 212, a patterned photoresist layer 312 is formed. As a result of removing the unexposed portion 308 , the patterned photoresist layer 312 includes an opening 314 , and the material layer 302 is exposed in the opening 314 .

[0038] refer to Figure 5 and 11 , method 200 includes block 214, where material layer 302 is etched using patterned photoresist layer 312 as an etch mask. In some embodiments, material layer 302 is etched using patterned photoresist layer 312 as an etch mask by a dry etching process 700, such as a reactive ion etching (RIE) process. In some examples, a fluorine-containing etchant gas (e.g., NF 3 CF 4 , SF 6 , CH 2 F 2 , CHF 3 , and / or C 2 F 6 ), oxygen-containing gases (e.g., O 2 or 3 ), chlorine-containing gases (such as Cl 2 , CHCl 3 , CCl 4 、SiCl 4 , and / or BCl 3 ), nitrogen-containing gases (such as N 2 or NH 2 ), bromine-containing gases (such as HBr and / or CHBr 3 ), iodine-containing gas, argon (Ar), other suitable gases and / or plasma or a combination thereof to perform the dry etching process 700. Fig.11In some embodiments shown, the dry etching process 700 forms a recess 316 in the material layer 302. Although the recess 316 is shown as not extending through the material layer 302, in alternative embodiments, it can extend through the material layer 302. The operation at box 214 can be applied to form a fin of a fin field effect transistor (FinFET), a fin structure for forming a multi-bridge channel (MBC) transistor, a pseudo gate stack formed during the manufacture of a FinFET or MBC transistor, a source / drain contact opening, a gate contact opening, a via opening, or a metal line trench. After forming the recess 316, the patterned photoresist layer 312 can be removed by ashing or selective etching.

[0039] Although not intended to be limiting, one or more embodiments of the present disclosure provide benefits for semiconductor devices and their formation processes. For example, the present disclosure provides an organometallic precursor in a negative photoresist. The organometallic precursor contains an aromatic bidentate ligand having a structural match for intermolecular coordination. An example of an organometallic precursor includes a 2,2'-bipyrazine molecule coordinated to a transition metal with high EUV absorption. The transition metal is also coordinated to EUV cleavable ligands, which may be cleaved by EUV radiation to form uncoordinated sites. When the aromatic bidentate ligand is an aromatic 2,2'-bipyrazine, two nitrogen atoms in the opposite side may be coordinated to the non-coordinated sites. The structural match of the intermolecular coordination and the π-π interaction of the aromatic ligands may lead to an ordered stacking of the layers. The ordered stacking produces a crystalline polymer structure, resulting in reduced defects (reduced scum), good LER and high contrast.

[0040] In one exemplary aspect, the present disclosure provides an organometallic precursor. The organometallic precursor comprises an aromatic bidentate ligand, a transition metal coordinated to the aromatic bidentate ligand, and an extreme ultraviolet (EUV) cleavable ligand coordinated to the transition metal. The aromatic bidentate ligand comprises a plurality of pyrazine molecules.

[0041] In some embodiments, the aromatic bidentate ligand comprises 2,2'-bipyrazine. In some implementations, the transition metal has a high atomic absorption cross section. In some cases, the transition metal is selected from tin (Sn), bismuth (Bi), antimony (Sb), indium (In) and tellurium (Te). In some embodiments, the organometallic precursor may further include poly (2-hydroxyethyl methacrylate) (pHEMA), poly (4-hydroxystyrene) (PHS), polyglycidyl ether or polyether polyol. In some embodiments, the EUV cleavable ligand comprises an alkenyl or carboxylate group. In some cases, the EUV cleavable ligand comprises a fluorine substituent.

[0042] In another exemplary aspect, the present disclosure relates to an extreme ultraviolet (EUV) photoresist precursor. The extreme ultraviolet (EUV) photoresist precursor comprises an aromatic bidentate ligand (including a first pyrazine ring and a second pyrazine ring), a transition metal coordinated to a nitrogen atom on the first pyrazine ring and a nitrogen atom on the second pyrazine ring, a first EUV cleavable ligand coordinated to the transition metal, and a second EUV cleavable ligand coordinated to the transition metal.

[0043] In some embodiments, the aromatic bidentate ligand comprises bipyrazine, and the first pyrazine ring is connected to the second pyrazine ring. In some embodiments, the aromatic bidentate ligand comprises 2,2'-bipyrazine. In some cases, the transition metal has a high atomic absorption cross section. In some embodiments, the transition metal is selected from tin (Sn) ions, bismuth (Bi) ions, antimony (Sb) ions, indium (In) ions and tellurium (Te) ions. In some embodiments, the EUV photoresist precursor may further include poly (2-hydroxyethyl methacrylate) (pHEMA), poly (4-hydroxystyrene) (PHS), polyglycidyl ether or polyether polyol. In some embodiments, the EUV cleavable ligand comprises an alkenyl or carboxylate group. In some cases, the EUV cleavable ligand comprises a fluorine substituent.

[0044] In yet another exemplary aspect, the present disclosure relates to a method. The method includes depositing a photoresist layer directly on a material layer, wherein the photoresist layer includes a precursor, the precursor includes an aromatic bidentate ligand, the aromatic bidentate ligand includes a first pyrazine ring and a second pyrazine ring, the first pyrazine ring includes a first nitrogen atom and a second nitrogen atom, the second pyrazine ring includes a first nitrogen atom and a second nitrogen atom; a transition metal coordinated to a first nitrogen atom on the first pyrazine ring and a first nitrogen atom on the second pyrazine ring; and a first EUV cleavable ligand and a second EUV cleavable ligand coordinated to the transition metal. The method may further include exposing a portion of the photoresist layer to EUV radiation to cleave the first EUV cleavable ligand and the second EUV cleavable ligand from the transition metal, and activating the second nitrogen atom on the first pyrazine ring and activating the second nitrogen atom on the second pyrazine ring.

[0045] In some embodiments, the aromatic bidentate ligand comprises 2,2'-bipyrazine. In some implementations, the deposition of the photoresist layer comprises supplying a first gaseous precursor to the material layer. The first gaseous precursor comprises an aromatic bidentate ligand, a transition metal coordinated to a first nitrogen atom on a first pyrazine ring and a first nitrogen atom on a second pyrazine ring, and a first halide group and a second halide group coordinated to the transition metal. The method further comprises supplying a second gaseous precursor to the material layer. The second gaseous precursor comprises a first EUV cleavable ligand and a second EUV cleavable ligand.

[0046] In some embodiments, depositing the photoresist layer includes depositing the photoresist layer using spin coating. In some cases, the method may further include baking the photoresist layer after the exposing to crosslink portions of the photoresist layer.

[0047] Some exemplary implementations are described below:

[0048] Embodiment 1. An organometallic precursor, comprising:

[0049] Aromatic bidentate ligands;

[0050] a transition metal coordinated to the aromatic bidentate ligand; and

[0051] an extreme ultraviolet (EUV) cleavable ligand coordinated to the transition metal,

[0052] The aromatic bidentate ligand comprises a plurality of pyrazine molecules.

[0053] Embodiment 2. The organometallic precursor of embodiment 1, wherein the aromatic bidentate ligand comprises 2,2'-bipyrazine.

[0054] Embodiment 3. The organometallic precursor of embodiment 1, wherein the transition metal has a high atomic absorption cross section.

[0055] Embodiment 4. The organometallic precursor according to embodiment 1, wherein the transition metal is selected from tin (Sn), bismuth (Bi), antimony (Sb), indium (In), and tellurium (Te).

[0056] Embodiment 5. The organometallic precursor according to embodiment 1, further comprising:

[0057] Poly(2-hydroxyethyl methacrylate) (pHEMA), poly(4-hydroxystyrene) (PHS), polyglycidyl ether or polyether polyol.

[0058] Embodiment 6. The organometallic precursor of embodiment 1, wherein the EUV cleavable ligand comprises an olefin group or a carboxylate group.

[0059] Embodiment 7. The organometallic precursor of embodiment 1, wherein the EUV cleavable ligand comprises a fluorine substituent.

[0060] Embodiment 8. An extreme ultraviolet (EUV) photoresist precursor, the precursor comprising:

[0061] an aromatic bidentate ligand comprising a first pyrazine ring and a second pyrazine ring;

[0062] a transition metal coordinated to the nitrogen atom on the first pyrazine ring and the nitrogen atom on the second pyrazine ring;

[0063] a first EUV cleavable ligand coordinated to the transition metal; and

[0064] A second EUV cleavable ligand is coordinated to the transition metal.

[0065] Embodiment 9. The EUV photoresist precursor according to embodiment 8,

[0066] wherein the aromatic bidentate ligand comprises bipyrazine,

[0067] wherein the first pyrazine ring is connected to the second pyrazine ring.

[0068] Embodiment 10. The EUV photoresist precursor of embodiment 8, wherein the aromatic bidentate ligand comprises 2,2'-bipyrazine.

[0069] Embodiment 11. The EUV photoresist precursor of embodiment 8, wherein the transition metal has a high atomic absorption cross section.

[0070] Embodiment 12. The EUV photoresist precursor according to embodiment 8, wherein the transition metal is selected from the group consisting of tin (Sn) ions, bismuth (Bi) ions, antimony (Sb) ions, indium (In) ions, and tellurium (Te) ions.

[0071] Embodiment 13. The EUV photoresist precursor according to embodiment 8, further comprising:

[0072] Poly(2-hydroxyethyl methacrylate) (pHEMA), poly(4-hydroxystyrene) (PHS), polyglycidyl ether or polyether polyol.

[0073] Embodiment 14. The EUV photoresist precursor according to embodiment 8, wherein the EUV cleavable ligand comprises an olefinic group or a carboxylate group.

[0074] Embodiment 15. The EUV photoresist precursor of embodiment 14, wherein the EUV cleavable ligand comprises a fluorine substituent.

[0075] Embodiment 16. A method of depositing a photoresist, the method comprising:

[0076] Depositing a photoresist layer directly on the material layer, wherein the photoresist layer comprises a precursor comprising:

[0077] an aromatic bidentate ligand, the aromatic bidentate ligand comprising a first pyrazine ring and a second pyrazine ring, the first pyrazine ring comprising a first nitrogen atom and a second nitrogen atom, the second pyrazine ring comprising a first nitrogen atom and a second nitrogen atom,

[0078] a transition metal coordinated to the first nitrogen atom on the first pyrazine ring and the first nitrogen atom on the second pyrazine ring, and

[0079] a first EUV cleavable ligand and a second EUV cleavable ligand coordinated to the transition metal; and

[0080] exposing a portion of the photoresist layer to EUV radiation to:

[0081] cleaving the first EUV cleavable ligand and the second EUV cleavable ligand from the transition metal, and

[0082] The second nitrogen atom on the first pyrazine ring and the second nitrogen atom on the second pyrazine ring are activated.

[0083] Embodiment 17. The method of embodiment 16, wherein the aromatic bidentate ligand comprises 2,2'-bipyrazine.

[0084] Embodiment 18. The method of embodiment 16, wherein the depositing of the photoresist layer comprises:

[0085] A first gaseous precursor is supplied to the material layer, the first gaseous precursor comprising:

[0086] Aromatic bidentate ligands,

[0087] a transition metal coordinated to the first nitrogen atom on the first pyrazine ring and the first nitrogen atom on the second pyrazine ring, and

[0088] a first halide group and a second halide group coordinated to the transition metal; and

[0089] supplying a second gaseous precursor to the material layer, the second gaseous precursor comprising:

[0090] The first EUV cleavable ligand and the second EUV cleavable ligand.

[0091] Embodiment 19. The method of embodiment 16, wherein the depositing of the photoresist layer comprises:

[0092] The photoresist layer is deposited using a spin coating method.

[0093] Embodiment 20. The method of embodiment 16, further comprising:

[0094] After exposure, the photoresist layer is baked to crosslink portions of the photoresist layer.

[0095] The foregoing summarizes the features of several embodiments so that those skilled in the art can better understand the various aspects of the present disclosure. Those skilled in the art will appreciate that they can easily use the present disclosure as a basis for designing or modifying other processes and structures to achieve the same purpose and / or achieve the same advantages as the embodiments described herein. Those skilled in the art will also appreciate that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and modifications herein without departing from the spirit and scope of the present disclosure.

Claims

1. An organometallic precursor, comprising: Aromatic bidentate ligands; a transition metal coordinated to the aromatic bidentate ligand; and an extreme ultraviolet cleavable ligand coordinated to the transition metal, wherein the aromatic bidentate ligand comprises a plurality of pyrazine molecules, wherein the aromatic bidentate ligand is 2,2'-bipyrazine, and The transition metal is selected from tin, bismuth, antimony, indium and tellurium.

2. The organometallic precursor according to claim 1, further comprising: Poly(2-hydroxyethyl methacrylate), poly(4-hydroxystyrene), polyglycidyl ether or polyether polyol.

3. The organometallic precursor of claim 1, wherein the EUV cleavable ligand comprises an olefin group or a carboxylate group.

4. The organometallic precursor of claim 1, wherein the EUV cleavable ligand comprises a fluorine substituent.

5. An extreme ultraviolet photoresist precursor, comprising: an aromatic bidentate ligand comprising a first pyrazine ring and a second pyrazine ring; a transition metal coordinated to the nitrogen atom on the first pyrazine ring and the nitrogen atom on the second pyrazine ring; a first extreme ultraviolet cleavable ligand coordinated to the transition metal; and a second extreme ultraviolet cleavable ligand coordinated to the transition metal, wherein the aromatic bidentate ligand is 2,2'-bipyrazine, and The transition metal is selected from the group consisting of tin, bismuth, antimony, indium and tellurium.

6. The EUV photoresist precursor according to claim 5, further comprising: Poly(2-hydroxyethyl methacrylate), poly(4-hydroxystyrene), polyglycidyl ether or polyether polyol.

7. The EUV photoresist precursor of claim 5, wherein the EUV cleavable ligand comprises an olefin group or a carboxylate group.

8. The EUV photoresist precursor of claim 7, wherein the EUV cleavable ligand comprises a fluorine substituent.

9. A method for depositing a photoresist, the method comprising: Depositing a photoresist layer directly on the material layer, wherein the photoresist layer comprises a precursor comprising: an aromatic bidentate ligand, the aromatic bidentate ligand comprising a first pyrazine ring and a second pyrazine ring, the first pyrazine ring comprising a first nitrogen atom and a second nitrogen atom, the second pyrazine ring comprising a first nitrogen atom and a second nitrogen atom, a transition metal coordinated to the first nitrogen atom on the first pyrazine ring and the first nitrogen atom on the second pyrazine ring, and a first extreme ultraviolet cleavable ligand and a second extreme ultraviolet cleavable ligand coordinated to the transition metal; and Exposing a portion of the photoresist layer to extreme ultraviolet radiation to causing the first EUV cleavable ligand and the second EUV cleavable ligand to cleave from the transition metal, and activating the second nitrogen atom on the first pyrazine ring and the second nitrogen atom on the second pyrazine ring, wherein the aromatic bidentate ligand is 2,2'-bipyrazine; and The transition metal is selected from the group consisting of tin, bismuth, antimony, indium and tellurium.

10. The method of claim 9, wherein depositing the photoresist layer comprises: A first gaseous precursor is supplied to the material layer, the first gaseous precursor comprising: Aromatic bidentate ligands, a transition metal coordinated to the first nitrogen atom on the first pyrazine ring and the first nitrogen atom on the second pyrazine ring, and a first halide group and a second halide group coordinated to the transition metal; and supplying a second gaseous precursor to the material layer, the second gaseous precursor comprising: The first extreme ultraviolet cleavable ligand and the second extreme ultraviolet cleavable ligand.

11. The method of claim 9, wherein depositing the photoresist layer comprises: The photoresist layer is deposited using a spin coating method.

12. The method according to claim 9, further comprising: After exposure, the photoresist layer is baked to crosslink portions of the photoresist layer.

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