PHOTOGRAPHIC VARNISH FOR SEMICONDUCER MANUFACTURING

Abstract

Organometallic precursor in an extreme ultraviolet photoresist precursor (EUV photoresist precursor), comprising: an aromatic bidentate ligand; a transition metal coordinated by the aromatic bidentate ligand; and an extreme ultraviolet cleavable (EUV cleavable) ligand coordinated to the transition metal, wherein the aromatic bidentate ligand comprises a variety of pyrazine molecules.

Description

PRIORITY DATA

[0001] This application claims priority over preliminary US patent application No. 63 / 085,305, filed on September 30, 2020, the full disclosure of which is hereby incorporated herein by reference. BACKGROUND

[0002] The integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced generations of ICs, each generation featuring smaller and more complex circuits than the previous one. As IC development has progressed, the functional density (i.e., the number of interconnected components per unit area of ​​the chip) has generally increased, while the geometric size (i.e., the smallest component (or trace) that can be produced using a manufacturing process) has decreased. This miniaturization process generally offers benefits by improving production efficiency and reducing associated costs. Such miniaturization has also increased the processing and manufacturing complexity of ICs, and similar developments in IC processing and manufacturing are needed to implement these advances.

[0003] In one exemplary aspect, photolithography is a process used in semiconductor microfabrication to selectively remove portions of a material layer. The process uses a radiation source to transfer a structure (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 exposed areas of the photosensitive layer. Bake-out processes can be performed before and / or after exposure, for example, in a pre-exposure bake-out and / or a post-exposure bake-out. Subsequently, in a development process, the exposed or unexposed areas are selectively removed using a developer solution, forming an exposure pattern in the material layer.To improve the resolution of the photolithography process and accommodate high-density integrated circuits (ICs), radiation sources with shorter wavelengths have been developed. One such source is extreme ultraviolet (EUV) radiation. While existing EUV photoresists are generally adequate for their intended purposes, they are not entirely satisfactory. Further improvements are desirable. List of characters

[0004] The present disclosure is best understood by referring to the following detailed description, which is read in conjunction with the accompanying figures. It is emphasized that, in accordance with standard industry practice, various features are not drawn to scale and are for illustrative purposes only. In fact, the dimensions of the various features may be enlarged or reduced as desired for the clarity of the discussion. Fig. Figure 1 schematically illustrates a molecular structure of a metal-organic precursor according to various aspects of the present disclosure. Fig. 2 and Fig. Figure 3 schematically illustrates changes in the coordination of organometallic precursor molecules as a result of EUV radiation incidence according to various aspects of the present disclosure. Fig. Figure 4 schematically illustrates an ordered crosslinking of organometallic precursor molecules according to various aspects of the present disclosure. Fig. Figure 5 illustrates a flowchart of a process 200 for structuring a workpiece according to various aspects of the present disclosure. Fig. Figures 6-11 illustrate partial cross-sectional views of a workpiece undergoing various steps of process 200. Fig. 5 is subjected to, according to various aspects of the present revelation. DETAILED DESCRIPTION

[0005] The following disclosure provides many different embodiments or exemplary embodiments for implementing various features of the provided subject matter. To simplify the present disclosure, specific examples of components and arrangements are described below. These are, of course, merely exemplary embodiments and are not intended to be limiting. For example, the formation of a first feature above or on top of a second feature in the following description may include embodiments in which the first and second features are formed in direct contact, and also embodiments in which additional features may be formed between the first and second features such that the first and second features may not be in direct contact. Furthermore, the present disclosure may repeat reference numerals and / or letters in the various examples.This repetition serves the purpose of simplicity and clarity and does not in itself imply any relationship between the various discussed embodiments and / or configurations.

[0006] Spatially relative terms such as "under," "below," "lower," "above," "upper," and the like, used here for the sake of simplicity, can be used to describe the relationship of one element or feature to another element(s) or feature(s), as illustrated in the figures. These spatially relative terms are intended to encompass different orientations of the device in use or operation, in addition to the orientation shown in the figures. The object may be oriented differently (rotated by 90 degrees or in other orientations), and the spatially relative descriptions used here can be interpreted accordingly.

[0007] When a number or range of numbers is described using terms like "approximately," "circa," and the like, the term is further intended to include numbers that fall within a reasonable range, taking into account variations inherent in manufacturing, as understood by the person skilled in the art. For example, based on known manufacturing tolerances associated with the production of a feature possessing a property associated with the number, the number or range of numbers will include a realistic range containing the described number, such as ±10%. For example, a material layer described as being "approximately 5 nm" thick may have dimensions in the range of 4.25 nm to 5.75 nm if the person skilled in the art is aware that manufacturing tolerances associated with the deposition of the material layer are ±15%.Furthermore, the present disclosure may repeat reference numerals and / or letters in the various examples. This repetition serves the purpose of simplicity and clarity and does not in itself establish a relationship between the various embodiments and / or configurations discussed.

[0008] The present disclosure relates generally to EUV photolithography and in particular to a metal-organic precursor in EUV photoresists.

[0009] Some well-known EUV photoresists exist as solutions comprising a cation species and an anion species. The anion species comprises a metal ion coordinated by EUV-stable ligands and bridging ligands. The bridging ligands act as crosslinking agents by coordinating to another metal ion. Examples of bridging ligands in a known EUV include oxalic ions (C₂O₄). 2-These EUV photoresists exhibit poor adhesion to various surfaces. To improve adhesion, surface treatments or adhesion promoter layers are necessary to ensure satisfactory bonding. Examples of adhesion promoter layers include hexamethyldisilazane (HMDS). Furthermore, because the bridging ligands are EUV-cleavable and also act as crosslinking agents, controlling the EUV-induced crosslinking process is challenging. On the one hand, some bridging ligands must be cleaved from the metal ions to create uncoordinated sites for crosslinking. On the other hand, some bridging ligands must remain coordinated to the metal ions to function as crosslinking agents. If no bridging ligands are cleaved, or if all of them are, the crosslinking may be unsatisfactory.Furthermore, a layer of a known EUV photoresist can exhibit a crosslinking gradient across its depth due to a lack of structural consistency. In some examples, the degree of crosslinking is higher near the top surface, while it is lower further away from the top surface. Such a crosslinking gradient can lead to foaming defects, poor line edge roughness (LER), and low lithographic contrast after development.

[0010] The present disclosure provides a metal-organic precursor in a photoresist comprising an aromatic bidentate ligand with structural similarity for intermolecular coordination. In one embodiment of the present disclosure, the metal-organic precursor comprises a 2,2'-bipyrazine molecule coordinated to a transition metal with high EUV absorption. The transition metal is also coordinated by EUV-cleavable ligands that can be cleaved by EUV radiation, forming uncoordinated sites. If the aromatic bidentate ligand is aromatic 2,2'-bipyrazine, two nitrogen atoms on opposite faces can coordinate to the uncoordinated sites. The structural similarity of the intermolecular coordination and the π-π interaction of the aromatic ligand can lead to an ordered packing of layers.The ordered packing results in a crystalline polymer structure, which in turn leads to a reduction in defects (foam reduction), good LER and high contrast.

[0011] The aromatic bidentate ligand of the present disclosure fulfills several criteria. First, as the name suggests, the aromatic bidentate ligand comprises at least one aromatic ring to provide a conjugated system and enable π-π stacking. Second, the aromatic bidentate ligand has a dentate number of 2. That is, the aromatic bidentate ligand comprises two atoms that can bind to a metal central ion in a coordination complex. The bidentate number of the aromatic bidentate ligand is not insignificant. Transition metal complexes can be characterized by coordination numbers from 1 to 12, but the most common coordination numbers are 2, 4, and 6. For metals with a large atomic absorption cross-section, such as those described in the present disclosure, the coordination number is greater than 4 and probably 6.If the metal is to be coordinated by two organometallic precursor molecules and still possess unsaturated sites for improved adhesion, the organometallic precursors must be either monodentate or bidentate. Since monodentate is less conducive to an ordered structure, bidentate was chosen. Third, the aromatic bidentate ligand comprises a symmetrical structure for ordered crosslinking. Fourth, in addition to the atoms providing dentateness, the aromatic bidentate ligand comprises EUV-activatable ligands for crosslinking. Fifth, the aromatic bidentate ligand can optionally comprise a planar structure to support π-π stacking, which is conducive to ordered interlayer interactions. Examples include 2,2'-bipyrazine (C8H6N4), 2,2'-bipyrimidine (C8H6N4), 3,3'-bipyridazine (C8H6Na), each of which comprises two linked heterocyclic aromatic rings.

[0012] Fig. Figure 1 illustrates a schematic molecular structure of an organometallic precursor molecule 100 according to aspects of the present disclosure. The organometallic precursor molecule 100 comprises an aromatic bidentate ligand (X) 102, an aromatic metal ion (M) 104 coordinated by 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 is understood that similar descriptions can be applied to other embodiments of the aromatic bidentate ligand 102. The organometallic precursor molecule 100 can also be composed of M a X b R cThe following expressions are used: M denotes the metal ion 104, R denotes the EUV cleavable ligand 106, and X denotes the aromatic bidentate ligand 102, where a = 1, b = 1, and c = 2. The metal ion 104 can comprise a metal exhibiting a large atomic absorption cross-section. Examples of the metal ion 104 include tin (Sn), bismuth (B1), antimony (Sb), indium (In), or tellurium (Te). Since the metal ion 104 can have six (6) coordination sites, the EUV cleavable ligand (R) 106 and the aromatic bidentate ligand (X) 102 together do not occupy all of the coordination sites, leaving up to two unsaturated (i.e., non-coordinated) sites available for adhesion improvement. In contrast to some known organometallic precursors, which exist in ionic form and are stabilized by a counterion, the organometallic precursor molecule 100 is charge-neutral.In some embodiments, the metal-organic precursor molecule 100 of the present disclosure can be prepared ex situ and then deposited onto a semiconductor device workpiece using spin coating. In some other embodiments, the metal-organic precursor molecule 100 can be deposited onto the semiconductor device workpiece using chemical vapor deposition (CVD) or atomic layer deposition (ALD).

[0013] In the illustrated embodiment, the aromatic bidentate ligand 102 can be 2,2'-bipyrazine, which comprises two pyrazine rings linked to each other at position 2 of the first pyrazine ring and at position 2' of the second pyrazine ring. The two pyrazine rings can be referred to as a first pyrazine ring and a second pyrazine ring. The first pyrazine ring comprises one nitrogen atom each at positions 1 and 4. The second pyrazine ring comprises one nitrogen atom each at positions 1' and 4'. The 2,2'-bipyrazine is coordinated to the metal ion 104 via the nitrogen atoms at position 1 of the first pyrazine ring and position 1' of the second pyrazine ring. The metal ion 104 is further coordinated by two EUV-cleavable ligands 106. The nitrogen atoms at position 4 of the first pyrazine ring and position 4' of the second pyrazine ring can be activated by EUV radiation.As described below, after activation, they can coordinate to a metal ion 104 from which one or more EUV-cleavable ligands 106 have been cleaved. The EUV-cleavable ligand 106 can comprise an alkenyl group or a carboxylate group. The alkenyl or carboxylate group can comprise hydrogen, fluorine, or an alkyl group. If present, alkyl groups in the EUV-cleavable ligands 106 can be linear, branched, or cyclic, and can comprise 1 to 6 carbon atoms. Both the alkenyl and the carboxylate groups comprise a double bond that can be cleaved by EUV radiation, thus conferring EUV cleavage to these EUV-cleavable ligands. The pyrazine rings are planar due to the π-conjugated system in each pyrazine ring. In fact, 2,2'-bipyrazine can adopt a trans-planar configuration.Therefore, the organometallic precursor molecule 100 can be symmetrical with respect to the bond between position 2 of the first pyrazine ring and position 2' of the second pyrazine ring.

[0014] Fig. 2 and Fig. Figure 3 schematically illustrates changes in the coordination of organometallic precursor molecules 100 as a result of EUV radiation irradiation. For illustrative purposes, in Fig. 2 and Fig. 3 three organometallic precursor molecules 100 shown. With reference to Fig. 2 can generate the incursion of EUV radicals, which can cleave the EUV-fissionable ligands 106, thereby creating free coordination sites on the metal ion 104 and activating the nitrogen atoms at position 4 or position 4'. As in Fig. As shown in Figure 2, the activated nitrogen atoms can be available for coordination to free coordination sites on the metal ions 104 of other organometallic precursor molecules 100 (represented as circles for easier illustration). It will now be shown that Fig. 3. During a bake-out process following exposure after EUV exposure, the activated nitrogen atoms at position 4 or 4' can coordinate to the available coordination sites on the metal ions 104 of another organometallic precursor molecule 100.

[0015] Due to the trans-planar configuration of the organometallic precursor molecules 100, crosslinking between organometallic precursor molecules 100 in a layer in a molecular plane can occur. Fig. Figure 4 illustrates an ordered crosslinking of the organometallic precursor molecules 100 in such a layer. For each organometallic precursor molecule 100, EUV irradiation can cleave the EUV-cleavable ligands 106 from the metal ion 104 and activate the nitrogen atoms at position 4 and position 4'. During the bake-out process after irradiation, the activated nitrogen atoms at position 4 (or position 4') coordinate to available sites on the metal ion 104. As shown in Fig. As shown in Figure 4, the metal ion 104 of a metal-organic precursor molecule 100 can be coordinated by two atoms at position 4 (or 4') of two other metal-organic precursor molecules 100, thereby crosslinking them. Simultaneously, the two nitrogen atoms at positions 4 and 4' of the same metal-organic precursor molecule 100 coordinate to two metal ions 104 of two other metal-organic precursor molecules. If each metal ion 104 is coordinated by four nitrogen atoms at position 4 (or 4'), the crosslinked metal-organic precursor molecules 100 can exhibit good short- 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 dominates the non-covalent interaction between layers. π-stacking promotes the creation of an ordered stacking of different layers (or molecular planes).The organometallic precursor molecules 100 of the present disclosure can generate a crystalline polymer structure due to the symmetrical structure of the organometallic precursor molecules 100 and the π-stacking of the aromatic pyrazine rings, which can provide uniform crosslinking, a reduction of defects, a reduction of foaming, an improvement in LER and a higher development contrast.

[0016] In general, a positive photoresist is a photoresist in which the exposed portion of the photoresist becomes soluble in the photoresist developer. The unexposed portion of the photoresist remains insoluble in the photoresist developer. A negative photoresist is a photoresist in which the exposed portion of the photoresist becomes insoluble in the photoresist developer. The unexposed portion of the photoresist is dissolved by the photoresist developer. Since EUV irradiation forms cross-links that reduce the solubility of the metal-organic precursor molecule 100 in a developer, the metal-organic precursor molecule 100 of the present disclosure can be an active component of a negative photoresist for EUV lithography. Fig. Figure 5 illustrates a flowchart of a process 200 for structuring a material layer on a workpiece using a negative photoresist comprising the metal-organic precursor molecule 100 described herein. Process 200 is merely an example and is not intended to limit the present disclosure to what is explicitly illustrated in process 200. Additional steps may be provided before, during, and after process 200, and some described steps may be substituted, omitted, or postponed for additional embodiments of the process. For the sake of simplicity, not all steps are described in detail herein. Process 200 is described below by reference to Fig. Figures 6-11 describe which partial cross-sectional views of a workpiece 300 are taken at different manufacturing phases according to embodiments of the method 200. Unless otherwise specified, in this application, identical reference numerals denote identical features.

[0017] With reference to Fig. 5 and Fig. 6. Method 200 comprises a block 202 in which a workpiece 300 is provided. The workpiece 300 comprises a substrate 301 and a layer of material 302 arranged above the substrate 301. It is noted that the substrate 301 is in Fig. 6 is illustrated with dashed lines and in Fig. Figures 7-11 have been omitted for the sake of simplicity. Substrate 301 can be an elemental semiconductor (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 arsenide 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 and / or calcium fluoride (CaF2); and / or combinations thereof.In some other embodiments, the substrate 301 can be a single-layer material with a uniform composition; alternatively, the substrate 301 can comprise multiple layers of material with similar or different compositions suitable for fabricating IC devices. In one example, the substrate 301 can be a silicon-on-insulator (SOI) substrate having a silicon semiconductor layer formed on a silicon oxide layer. The substrate 301 can 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 transistors, diodes, resistors, capacitors, inductors, varactor diodes, other suitable devices, and / or combinations thereof.

[0018] The material layer 302 above the substrate 301 represents a top layer on which a photoresist layer 304 (described below) is deposited. In some embodiments, the material layer 302 can be a dielectric layer serving as a hard mask layer, bottom antireflective coating (BARC), or insulating layer. In these embodiments, the material layer 302 can comprise silicon oxide, silicon nitride, silicon oxynitride, silicon carbonitride, silicon oxycarbonitride, a metal oxide, silicon carbide, or silicon oxycarbide.Examples of metal oxides can include high-k dielectric materials such as titanium oxide (TiO2), hafnium zirconium oxide (HfZrO), tantalum oxide (Ta2O5), hafnium silicon oxide (HfSiO4), zirconium oxide (ZrO2), zirconium silicon oxide (ZrSiO2), lanthanum oxide (La2O3), aluminum oxide (Al2O3), zirconium oxide (ZrO), yttrium oxide (Y2O3), SrTiO3 (STO), BaTiO3 (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)TiO3 (BST). In some other embodiments, the material layer 302 can comprise a semiconductor material, such as silicon (Si), germanium (Ge), gallium arsenide (GaAs), gallium phosphide (GaP), gallium nitride (GaN), or silicon germanium (SiGe). In further embodiments, the material layer 302 can comprise a polymer layer, such as a polyimide layer or a polymeric BARC layer.In further embodiments, the material layer 302 can comprise 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). If the material layer 302 comprises functional surface groups, such as a hydroxyl group or an amino group, the material layer 302 can adhere well to a subsequently deposited photoresist layer 304, since the photoresist layer 304 comprises the organometallic precursor molecule 100, which has non-coordinated adhesion sites.In some embodiments in which the material layer 302 can catalyze premature crosslinking of the photoresist layer 304 (described below), a very thin silicon oxide layer or a very thin polymer layer can be deposited on the material layer 302 in block 202 prior to the deposition of the photoresist layer.

[0019] With reference to Fig. 5 and Fig. In section 6, the process 200 comprises a block 204 in which a photoresist layer 304 is deposited onto the material layer 302. The photoresist layer 304 comprises the above-described organometallic precursor molecule 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 molecule 100, together with additives and surfactants, may be dispersed or dissolved in a dispersion or solution and then applied as a coating to the material layer 302.In some cases, the solution for coating the photoresist layer 304 can also include other crosslinkable polymers, such as poly(2-hydroxyethyl methacrylate) (pHEMA), poly(4-hydroxystyrene) (PHS), polyglycidyl ether, or polyether polyol. The inclusion of these other crosslinkable polymers can enhance the crosslinking reaction after EUV exposure. When the photoresist layer 304 is deposited using ALD or CVD, gaseous precursors of the metal-organic precursor molecule 100 can be directed to the material layer 302, where the gaseous precursors react with each other and with the material layer 302 to form the photoresist layer 304. In some cases, the gaseous precursors can comprise a first gaseous precursor and a second gaseous precursor. The first gaseous precursor can comprise a halogenated EUV-cleavable ligand, such as an alkene halide.The second gaseous precursor can comprise the metal ion 104 coordinated by the aromatic bidentate ligand 102 and halides. The halogen components allow the gaseous precursors to exist in gaseous form. During the CVD or ALD process, the material layer 302 can be heated, and the halogen components can be removed when the first and second gaseous precursors come into contact with the heated material layer 302, thereby forming the organometallic precursor molecule 100 in the photoresist layer 304.

[0020] With reference to Fig. 5 and Fig. In section 7, process 200 includes a block 206 in which a pre-exposure treatment process 400 is performed. This pre-exposure treatment process 400 is also referred to as the post-application treatment process 400. The pre-exposure treatment process 400 facilitates the outgassing of unwanted species or removes excess moisture from the photoresist layer 304. If gaseous precursors are used to deposit the photoresist layer 304, the unwanted species may include byproducts or leaving groups from the CVD or ALD process. Examples may include halide-containing species. Depending on the properties of the species to be removed, the pre-exposure treatment process 400 may include a bake-out process, an infrared curing process, an ultraviolet curing process (UV curing process), or a visible light curing process.In some alternative embodiments where unwanted species need to be neutralized, the pre-exposure treatment process may include modifying the surface of the photoresist layer 304 with a reactive gas, such as silane (SiH4). If the pre-exposure treatment process 400 includes a bake-out process, the bake-out temperature may be between approximately 60 °C and approximately 170 °C.

[0021] With reference to Fig. 5 and Fig. In section 8, the process 200 comprises a block 208 in which the photoresist layer 304 is exposed with structured radiation. The exposure at block 208 can be carried out using a lithography system 500, which is located in Fig. Figure 8 is shown schematically. The lithography system 500 can also generally be referred to as a scanner that can be operated to perform lithographic processes that include exposure with a particular radiation source and in a specific exposure mode. In at least some of the present embodiments, the lithography system 500 comprises an extreme ultraviolet lithography system (EUV lithography system) designed to expose a photoresist layer, for example, the photoresist layer 304, with EUV radiation. The lithography system 500 from Fig. 8 comprises a variety of subsystems, such as an EUV source 502, an illumination device 504, a mask stage 506 configured to hold a mask 508, a projection optic 510, and a substrate stage 514 configured to hold a workpiece, such as the workpiece 300. A general description of the operation of the lithography system 500 can be as follows: EUV radiation from the EUV source 502 is directed to the illumination device 504 (which includes a set of reflective mirrors) and projected onto the reflective mask 508. A reflected mask image is directed to the projection optic 510, which focuses the EUV light and projects it onto the workpiece 300 to expose an EUV photoresist layer deposited thereon.In various examples, each subsystem of the Lithography System 500 can also be housed in a high vacuum environment and therefore operated in a high vacuum environment, for example to reduce the atmospheric absorption of EUV light.

[0022] The EUV source 502 can be used to generate the EUV radiation in the embodiments described herein. In some embodiments, the EUV source 502 comprises a plasma source, such as discharge-produced plasma (DPP) or laser-produced plasma (LPP). In some examples, the EUV radiation can comprise radiation with a wavelength centered at approximately 13.5 nm. In some embodiments, the EUV source 502 also comprises a collector that can be used to collect EUV radiation generated by the plasma source and direct it to imaging optics, such as the illumination device 504. As described above, EUV radiation is directed from the EUV source 502 to the illumination device 504.In some embodiments, the illumination device 504 may include reflective optics, for example, a single mirror or a system of multiple mirrors, to direct radiation from the EUV source 502 onto the mask table 506, in particular to the mask 508 held on the mask table 506. In some examples, the illumination device 504 may include a zone plate, for example, to improve the focusing of the EUV radiation. In some embodiments, the illumination device 504 may be configured to shape the transmitted EUV radiation according to a specific pupil shape, including, for example, a dipole shape, a quadrupole shape, annular shape, a single-beam shape, a multi-beam shape, and / or a combination thereof. In some embodiments, the illumination device 504 may be operated to adjust the mirrors (i.e.,The mirrors of the lighting device 504 can be configured to provide the desired illumination to the mask 508. In one example, the mirrors of the lighting device 504 are configurable to reflect EUV radiation towards different illumination positions. In some embodiments, additional configurable mirrors can be provided upstream of the lighting device 504, which can be used to direct the EUV radiation to different illumination positions within the mirrors of the lighting device 504. In some embodiments, the lighting device 504 is configured to provide on-axis illumination (ONI) to the mask 508. In some embodiments, the lighting device 504 is configured to provide off-axis illumination (OAI) to the mask 508.It should be noted that the optics used in the EUV lithography system 500, in particular the optics used for the illumination device 504 and the projection optics 510, may include mirrors with multilayer thin-film coatings, which are referred to as Bragg reflectors. Such a multilayer thin-film coating may, for example, comprise alternating layers of Mo and Si, which provide high reflectivity at EUV wavelengths (e.g., approximately 13 nm).

[0023] As described above, the lithography system 500 also includes the mask stage 506, which is configured to hold the mask 508. Since the lithography system 500 can be housed in and therefore operated in a high-vacuum environment, the mask stage 506 can include an electrostatic holding device (e-chuck) to hold the mask 508. The mask 508, like the optics of the EUV lithography system 500, is reflective. As in the example in Fig. As illustrated in Figure 8, radiation is reflected from the mask 508 and directed to the projection optics 510, which collects the EUV radiation reflected from the mask 508. The EUV radiation collected by the projection optics 510 (reflected from the mask 508) carries, for example, an image of the structure defined by the mask 508. In various embodiments, the projection optics 510 image the structure of the mask 508 onto the workpiece 300, which is held on the substrate table 514 of the lithography system 500. In particular, in various embodiments, the projection optics 510 focuses the collected EUV light and projects it onto the workpiece 300 to expose the photoresist layer 304 on the workpiece 300. As described above, the projection optics 510 can comprise reflective optics, such as those used in EUV lithography systems like the lithography system 500.In some embodiments, the illumination device 504 and the projection optics 510 are together referred to as the optical module of the lithography system 500.

[0024] In some embodiments, the lithography system 500 also includes a pupil phase modulator 512 to modulate the optical phase of the EUV radiation guided by the mask 508 such that the light has a phase distribution along a projection pupil plane. In some embodiments, the pupil phase modulator 512 includes a mechanism for adjusting the reflecting mirrors of the projection optics 510 for phase modulation. For example, in some embodiments, the mirrors of the projection optics 510 are configurable to reflect the 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 arranged on the projection pupil plane.For example, the pupil filter can be used to filter out certain spatial frequency components of the EUV radiation reflected by the mask 508. In some embodiments, the pupil filter can serve as a phase-pupil filter, modulating the phase distribution of the light guided through the projection optics 510.

[0025] As in Fig. As shown in Figure 8, when using the lithography system 500, an exposed section 310 of the photoresist layer 304 is exposed with EUV radiation, while an unexposed section 308 remains unexposed. The metal-organic precursor molecule 100 in the exposed section 310 of the photoresist layer 304 is crosslinked. With reference to Fig. 1 and Fig. 2. The EUV radiation of the lithography system 500 generates, in particular, radicals. The radicals cleave the EUV-cleavable ligands 106 from the metal ion 104. The nitrogen atoms at position 4 or 4' are activated and coordinate to another metal ion that has a non-coordinated site. The aromatic bidentate ligand 102 serves as a bridging ligand in the crosslinking process. Due to the lack of radicals, this crosslinking does not occur in the unexposed section 308. As above with reference to Fig. As described in section 4, due to the trans-planar configuration of the organometallic precursor molecules 100, crosslinking between organometallic precursor molecules 100 in a layer can occur in a molecular plane. For each organometallic precursor molecule 100 in the photoresist layer 304, EUV exposure can cleave the EUV-cleavable ligands 106 from the metal ion 104 and activate the nitrogen atoms at position 4 and position 4' of the aromatic bidentate ligand 102.

[0026] With reference to Fig. 5 and Fig. In section 9, the process 200 comprises a block 210 in which a post-exposure bake-out process 600 is performed. In some reactions, a bake-out temperature or bake-out temperature profile for the post-exposure bake-out process 600 is selected to facilitate crosslinking and ensure the removal of the leaving group generated during the EUV exposure process in block 208. The bake-out temperature of the post-exposure bake-out process 600 can range from approximately 150 °C to approximately 300 °C. During the post-exposure bake-out process 600, the activated nitrogen atoms at position 4 (or 4') of a metal-organic precursor molecule 100 in the exposed section 310 coordinate to available sites on the metal ions 104 of two adjacent metal-organic precursor molecules 100.The metal ion 104 of a single organometallic precursor molecule 100 can be coordinated by two atoms at position 4 (or 4') of two other organometallic precursor molecules 100, thereby crosslinking them. If each metal ion 104 is coordinated by four nitrogen atoms at position 4 (or 4'), the crosslinked organometallic precursor molecules 100 can exhibit good short- and long-range order in each layer. Between different layers (or molecular planes), π-stacking (or pi-stacking or π-π-stacking) between aromatic pyrazine rings dominates the non-covalent interaction between layers. π-stacking promotes the creation of an ordered stacking of different layers (or molecular planes).The organometallic precursor molecules 100 of the present disclosure can, due to the symmetrical structure of the organometallic precursor molecules 100 and the π-stacking of the aromatic pyrazine rings, form a crystalline polymer structure that can provide uniform crosslinking, a reduction in defects, a reduction in foaming, an improvement in LER, and higher development contrast. The leaving groups removed in block 210 can comprise EUV-cleavable ligands 106, halide-containing species, or combinations thereof.

[0027] With reference to Fig. 5 and Fig. In section 10, process 200 comprises a block 212 in which the exposed photoresist layer 304 is developed to form a structured photoresist layer 312. In block 212, a developer solution is used to remove the unexposed section 308, which was not crosslinked in block 208. The developer solution is selected to selectively dissolve and remove the (uncrosslinked) unexposed section 308 while leaving the (crosslinked) exposed section 310 of the photoresist layer 304 substantially intact. A suitable developer solution may include solvents such as n-butyl acetate, ethanol, hexane, benzene, toluene, water, isopropanol (IPA), or 2-heptanone. In some embodiments, block 212 may also include one or more defoaming or rinsing processes to remove any remaining photoresist layer 304 or other residues that may be present.After completion of the processes in block 212, the structured photoresist layer 312 is formed. Due to the removal of the unexposed section 308, the structured photoresist layer 312 includes an opening 314, and the material layer 302 is exposed in the opening 314.

[0028] With reference to Fig. 5 and Fig. In section 11, the method 200 comprises a block 214 in which the material layer 302 is etched using the structured photoresist layer 312 as an etching mask. In some embodiments, the material layer 302 is etched using the structured photoresist layer 312 as an etching mask with a dry etching process 700, for example, a reactive ion etching (RIE) process. In some examples, the dry etching process 700 can be implemented using an etching gas comprising a fluorine-containing etching gas (e.g., NF3, CF4, SF6, CH2F2, CHF3, and / or C2F6), an oxygen-containing gas (e.g., O2 or O3), a chlorine-containing gas (e.g., Cl2, CHCl3, CCl4, SiCl4, and / or BCl3), a nitrogen-containing gas (e.g., N2 or NH2), a bromine-containing gas (e.g., HBr and / or CHBr3), an iodine-containing gas, argon (Ar), other suitable gases, and / or plasmas, or combinations thereof. In some embodiments described in Fig.As represented in Figure 11, the dry etching process 700 forms a depression 316 in the material layer 302. Although the depression 316 is shown as not extending through the material layer 302, in alternative embodiments it can extend through the material layer 302. The processes in Block 214 can be applied to form fins of a fin field-effect transistor (FinFET), a fin-shaped structure for forming an MBC (multi-bridge-channel) transistor, a dummy gate stack formed during the fabrication of a FinFET or MBC transistor, a source / drain contact opening, a gate contact opening, a via opening, or a metal conduit trench. After the formation of the depression 316, the structured photoresist layer 312 can be removed by ashing or selective etching.

[0029] One or more embodiments of the present disclosure offer advantages for a semiconductor device and its formation process, but they are not intended to be limiting. For example, the present disclosure provides a metal-organic precursor in a negative photoresist. The metal-organic precursor comprises an aromatic bidentate ligand with structural compatibility for intermolecular coordination. An example of the metal-organic precursor includes a 2,2'-bipyrazine molecule coordinated to a transition metal with high EUV absorption. The transition metal is also coordinated by EUV-cleavable ligands that can be cleaved off by EUV radiation, forming uncoordinated sites. If the aromatic bidentate ligand is aromatic 2,2'-bipyrazine, two nitrogen atoms on opposite faces can coordinate to the uncoordinated sites.The structural similarity of the intermolecular coordination and the π-π interaction of the aromatic ligand can lead to an ordered packing of layers. This ordered packing results in a crystalline polymer structure, which in turn leads to defect reduction (foam reduction), good LER, and high contrast.

[0030] In one exemplary aspect, the present disclosure relates to the provision of an organometallic precursor. The organometallic precursor comprises an aromatic bidentate ligand, a transition metal coordinated to the aromatic bidentate ligand, and an extreme ultraviolet cleavage (EUV cleavage) ligand coordinated to the transition metal. The aromatic bidentate ligand comprises a variety of pyrazine molecules.

[0031] In some embodiments, the aromatic bidentate ligand comprises 2,2'-bipyrazine. In some reactions, the transition metal exhibits a large atomic absorption cross-section. In some cases, the transition metal is selected from a group consisting of tin (Sn), bismuth (Bi), antimony (Sb), indium (In), and tellurium (Te). In some embodiments, the organometallic precursor may further comprise poly(2-hydroxyethyl methacrylate) (pHEMA), poly(4-hydroxystyrene) (PHS), polyglycidyl ether, or polyether polyol. In some embodiments, the EUV-cleavable ligand comprises an alkenyl group or a carboxylate group. In some cases, the EUV-cleavable ligand may comprise a fluorine substituent.

[0032] In another exemplary aspect, the present disclosure relates to an extreme ultraviolet photoresist precursor (EUV photoresist precursor). The extreme ultraviolet photoresist precursor (EUV photoresist precursor) comprises an aromatic bidentate ligand comprising a first pyrazine ring and a second pyrazine ring, a transition metal coordinated by a nitrogen atom in the first pyrazine ring and a nitrogen atom in 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.

[0033] In some embodiments, the aromatic bidentate ligand comprises bipyrazine, and the first pyrazine ring is linked to the second pyrazine ring. In some reactions, the aromatic bidentate ligand comprises 2,2'-bipyrazine. In some cases, the transition metal has a large atomic absorption cross-section. In some embodiments, the transition metal is selected from a group consisting of a tin ion (Sn ion), a bismuth ion (Bi ion), an antimony ion (Sb ion), an indium ion (In ion), and a tellurium ion (Te ion). In some embodiments, the EUV photoresist precursor may further comprise poly(2-hydroxyethyl methacrylate) (pHEMA), poly(4-hydroxystyrene) (PHS), polyglycidyl ether, or polyether polyol. In some embodiments, the EUV cleavable ligand comprises an alkenyl group or a carboxylate group. In some cases, the EUV cleavable ligand may include a fluorine substituent.

[0034] In a further exemplary aspect, the present disclosure relates to a process. The process comprises depositing a photoresist layer directly onto a material layer, wherein the photoresist layer comprises a precursor comprising an aromatic bidentate ligand, the first pyrazine ring comprising a first nitrogen atom and a second nitrogen atom, and the second pyrazine ring comprising a first nitrogen atom and a second nitrogen atom, a transition metal coordinated to the first nitrogen atom in the first pyrazine ring and the first nitrogen atom in the second pyrazine ring, and a first EUV cleavable ligand and a second EUV cleavable ligand coordinated to the transition metal.The process can further include exposing a section of the photoresist layer with EUV radiation to cleave the first EUV cleavable ligand and the second EUV cleavable ligand from the transition metal and to activate the second nitrogen atom in the first pyrazine ring and the second nitrogen atom in the second pyrazine ring.

[0035] In some embodiments, the aromatic bidentate ligand comprises 2,2'-bipyrazine. In some embodiments, the deposition of the photoresist layer comprises the introduction of a first gaseous precursor to the material layer. The first gaseous precursor comprises the aromatic bidentate ligand, the transition metal coordinated by the first nitrogen atom in the first pyrazine ring and the first nitrogen atom in the second pyrazine ring, and a first and a second halide group coordinated to the transition metal. The process further comprises the introduction of a second gaseous precursor to the material layer. The second gaseous precursor comprises the first EUV cleavable ligand and the second EUV cleavable ligand.

[0036] In some embodiments, the deposition of the photoresist layer includes deposition of the photoresist layer using spin coating. In some cases, the method may further include, after exposure, baking out the photoresist layer to crosslink the section of the photoresist layer.

[0037] The foregoing outlines features of several embodiments so that the person skilled in the art can better understand the aspects of the present disclosure. The person skilled in the art should be aware that they can readily use the present disclosure as a basis for designing or modifying other processes and structures to achieve the same purposes and / or the same advantages as the embodiments presented herein. The person skilled in the art should also recognize that such equivalent designs do not deviate from the spirit and scope of the present disclosure and that they can make various changes, substitutions, and modifications to them without deviating from the spirit and scope of the present disclosure. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 63 / 085305

[0001]

Claims

[1] Organometallic precursor comprising: an aromatic bidentate ligand; a transition metal coordinated by the aromatic bidentate ligand; and an extreme ultraviolet cleavable (EUV-cleavable) ligand coordinated to the transition metal, wherein the aromatic bidentate ligand comprises a plurality of pyrazine molecules. [2] The organometallic precursor of claim 1, wherein the aromatic bidentate ligand comprises 2,2'-bipyrazine. [3] The organometallic precursor according to claim 1 or 2, wherein the transition metal has a large atomic absorption cross section. [4] An organometallic precursor according to any one of the preceding claims, wherein the transition metal is selected from a group consisting of tin (Sn), bismuth (Bi), antimony (Sb), indium (In) and tellurium (Te). [5] An organometallic precursor according to any one of the preceding claims, further comprising: Poly(2-hydroxyethyl methacrylate) (pHEMA), poly(4-hydroxystyrene) (PHS), polyglycidyl ether or polyether polyol. [6] An organometallic precursor according to any one of the preceding claims, wherein the EUV-cleavable ligand comprises an alkenyl group or a carboxylate group. [7] An organometallic precursor according to any one of the preceding claims, wherein the EUV-cleavable ligand comprises a fluorine substituent. [8] Extreme ultraviolet photoresist precursor (EUV photoresist precursor), comprising: an aromatic bidentate ligand comprising a first pyrazine ring and a second pyrazine ring; a transition metal coordinated by a nitrogen atom in the first pyrazine ring and a nitrogen atom in 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. [9] EUV photoresist precursor according to claim 8, wherein the aromatic bidentate ligand comprises bipyrazine, wherein the first pyrazine ring is connected to the second pyrazine ring. [10] The EUV photoresist precursor of claim 8 or 9, wherein the aromatic bidentate ligand comprises 2,2'-bipyrazine. [11] The EUV photoresist precursor according to any one of claims 8 to 10, wherein the transition metal has a large atomic absorption cross section. [12] The EUV photoresist precursor according to any one of claims 8 to 11, wherein the transition metal is selected from a group consisting of a tin ion (Sn ion), a bismuth ion (Bi ion), an antimony ion (Sb ion), an indium ion (In ion) and a tellurium ion (Te ion). [13] EUV photoresist precursor according to any one of claims 8 to 12, further comprising: Poly(2-hydroxyethyl methacrylate) (pHEMA), poly(4-hydroxystyrene) (PHS), polyglycidyl ether or polyether polyol. [14] The EUV photoresist precursor according to any one of claims 8 to 13, wherein the EUV-cleavable ligand comprises an alkenyl group or a carboxylate group. [15] The EUV photoresist precursor of claim 14, wherein the EUV-cleavable ligand comprises a fluorine substituent. [16] A method comprising: Depositing a photoresist layer directly onto a material layer, wherein the photoresist layer comprises a precursor comprising: an aromatic bidentate ligand comprising a first pyrazine ring and a second pyrazine ring, wherein the first pyrazine ring comprises a first nitrogen atom and a second nitrogen atom and the second pyrazine ring comprises a first nitrogen atom and a second nitrogen atom, a transition metal coordinated by the first nitrogen atom in the first pyrazine ring and the first nitrogen atom in the second pyrazine ring, and a first EUV-cleavable ligand and a second EUV-cleavable ligand coordinated to the transition metal; and Exposing a section of the photoresist layer to EUV radiation to: to cleave the first EUV-cleavable ligand and the second EUV-cleavable ligand from the transition metal and to activate the second nitrogen atom in the first pyrazine ring and the second nitrogen atom in the second pyrazine ring. [17] The process of claim 16, wherein the aromatic bidentate ligand comprises 2,2'-bipyrazine. [18] The method of claim 16 or 17, wherein depositing the photoresist layer comprises: Supplying a first gaseous precursor to the material layer, the first gaseous precursor comprising: the aromatic bidentate ligand, the transition metal coordinated by the first nitrogen atom in the first pyrazine ring and the first nitrogen atom in 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, wherein the second gaseous precursor comprises: the first EUV-cleavable ligand and the second EUV-cleavable ligand. [19] A method according to any one of claims 16 to 18, wherein depositing the photoresist layer comprises: Depositing the photoresist layer using spin coating. [20] A method according to any one of claims 16 to 19, further comprising: After exposure, bake the photoresist layer to crosslink the section of the photoresist layer.