Deposition of crystalline boron nitride films

Abstract

The disclosed and claimed subject matter relate to compositions and methods for forming a crystalline boron-containing film.

Description

Docket No. P24-266-SEC-WO01DEPOSITION OF CRYSTALLINE BORON NITRIDE FILMSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to United States Provisional Patent Application number 63 / 733,872, filed on December 13, 2024, the entire contents of which are incorporated by reference herein in their entirety.FIELD

[0002] The disclosed and claimed subject matter relate to compositions and methods for forming a polycrystalline boron-containing film. More specifically, described herein are compounds, composition and methods including same, for the formation of a stoichiometric or a non-stoichiometric polycrystalline boron-containing film or material at one or more deposition temperatures of 600 °C or less.BACKGROUND

[0003] Example technologies that can employ a high-quality ALD boron nitride layer of the disclosure include insulating layers in a MISFET (metal-insulator- semiconductor field effect transistor), interconnect covering, such as copper, to help prevent power loss, lower resistivity, and prevent interconnect failure from power overloading. The h-BN would be especially useful when low k and high thermal boundary conductance or low K and higher than SiQ? thermal conductivity is needed. Other applications include a thermal interface material in back end of line to heat spreaders . Other applications include FinFETs, DRAM, flash memory, etc. Additional applications include as an interfacial layer of amorphous or crystalline BN that is deposited prior to dielectric deposition in MOSFET (metal-oxide-semiconductor FET) device architectures to prevent substrate diffusion into the high k material, thereby producing a device with a lower density of interfacial traps (Dit). Thus far, boron precursors such as haloboranes (e.g., BCE), trialkylborane or boron alkoxide precursors have been used for boron doped films.

[0004] Haloborane compounds such as BCE and BBrs are used to deposit boron nitride films by ALD, however, there is a concern with residual halides in the films which may negatively impact electrical performance. It is also known that aminoboraneDocket No. P24-266-SEC-WO01 compounds such as (NfeN^B can be used to deposit boron nitride films by ALD, however, while these films can be deposited using N2 PEALD processes, the step coverage performance of N2 based PEALD processes is poor. To date, it has not been possible to deposit crystalline boron nitride films from aminoborane precursors using NH3 based PEALD processes at temperatures below 500 °C.

[0005] Another problem with prior art boron nitrite precursors in ALD is the poor deposition at the bottom of features that typically leads to voids in a gap-fill process. The gap-fill process is a very important stage of semiconductor manufacturing as it is used to fill a high aspect ratio gap (or feature) with an insulating or conducting material. For example, shallow trench isolation, inter-metal dielectric layers, passivation layers, dummy gate, etc. As device geometries shrink (e.g., critical dimensions < 20 nm) and thermal budgets are reduced, void-free filling of high aspect ratio spaces (e.g., AR>10:l) becomes increasingly difficult due to limitations of conventional deposition processes.

[0006] Most deposition methods-including boron nitride depositions processes - deposit more material on the top region or on the walls of a trench than on the bottom region of a structure. The process often forms a mushroom shape film profile. As a result, the top part of a high aspect ratio structure sometimes pinches off prematurely leaving seams / voids within the structure's lower portions. This problem is more prevalent in small features.

[0007] Accordingly, there is a need for precursors and processes that can deposit crystalline boron nitride especially hexagonal boron nitride (aka h-BN) at temperatures of 600 °C or less by atomic layer deposition.SUMMARY

[0008] Polycrystalline boron nitride films can be deposited from mixed haloaminoborane precursors such as, for example, B(NMe2)2Br, or other boron precursors using nitrogen-containing plasma, followed by inert gas plasma annealing. Unexpectedly, it has been found that the as-deposited boron nitride films are crystalline at temperatures of 600 °C or less, preferably 500 °C or less, most preferably 400 °C or less.

[0009] The disclosed and claimed subject matter provides a method to deposit crystalline boron nitride onto at least one surface of a substrate which includes, consists essentially of or consists of the steps of:(a) providing a substrate in a reactor;Docket No. P24-266-SEC-WO01(b) providing to the at least one surface of the substrate a boron-containing precursor selected from a trialkylborane, borazine or a derivative thereof and a compound having the structure of Formula I:B(NR1R2)nX3.n(I), wherein R1is selected from a linear Ci to Cio alkyl group, a branched C3 to Cio alkyl group, a linear or branched C3 to Cio alkenyl group, a linear or branched C3 to Cio alkynyl group, a Ci to Co dialkylamino group, an electron withdrawing group, and a C4 to Cio aryl group; R2is selected from hydrogen, a linear Ci to Cio alkyl group, a branched C3 to Cio alkyl group, a linear or branched C3 to Ce alkenyl group, a linear or branched C3 to Ce alkynyl group, a Ci to Ce dialkylamino group, a Ce to Cio aryl group, a linear or branched Ci to Ce fluorinated alkyl group, an electron withdrawing group, and a C4 to Cio aryl group; X is Cl, Br, I, or F; and n = 1 or 2, wherein R1and R2are optionally linked together to form a ring selected from a substituted or unsubstituted aromatic ring or a substituted or unsubstituted aliphatic ring, and wherein R1and R2may be the same moiety or different moieties;(c) purging the reactor with a purge gas;(d) providing to the at least one surface of the substrate a nitrogen -containing source;(e) purging the reactor with a purge gas;(f) introducing into the reactor at least an inert ICP gas plasma such as argon under constant or selective DC or RF bias applied on the substrate side; and(g) purging the reactor with a purge gas.Steps b through g are repeated until a desired thickness of the crystalline boron nitride film is obtained. In one aspect of this embodiment, the boron-containing film is deposited using a deposition process selected from chemical vapor deposition and atomic layer deposition.

[0010] The embodiments of the disclosed and claimed subject matter can be used alone or in combinations with each other.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings, which are included to provide a further understanding of the disclosed subject matter and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosed subject matter and together with the description serve to explain the principles of the disclosed subjectDocket No. P24-266-SEC-WO01 matter. In the drawings:

[0012] FIG. 1 is a selective substrate bias atomic layer annealing (ALA) process using bias wherein bromobis(dimethylamino)borane (BBB or BBDMAB) is boron- containing precursor;

[0013] FIG. 2 illustrates the crystal structure of the proposed ALA BN on the Si (100) substrate;

[0014] FIG. 3 illustrates EELSs spectrum acquired at collection angle 42 mrads;

[0015] FIGs. 4(a)-(c) illustrates saturation behavior of trichloroborazine (TCB) in the ALA process using TCB as boron precursor;

[0016] FIGs. 5(a)-(b) illustrate HRTEM comparison of PEALD and ALA BN films in terms of microstructure and electrical performance; and

[0017] FIGs. 6(a)-(d) illustrate self-limiting growth behavior of BN films deposited using the BBDMAB precursor.DEFINITIONS

[0018] Unless otherwise stated, the following terms used in the specification and claims shall have the following meanings for this application.

[0019] For ease of reference, “microelectronic device” corresponds to semiconductor substrates, flat panel displays, phase change memory devices, solar panels and other products including solar cell devices, photovoltaics, and microelectromechanical systems (MEMS), manufactured for use in microelectronic, integrated circuit, energy collection, or computer chip applications. It is to be understood that the terms “microelectronic device,” “microelectronic substrate” and “microelectronic device structure” are not meant to be limiting in any way and include any substrate or structure that will eventually become a microelectronic device or microelectronic assembly. The microelectronic device can be patterned, blanketed, a control and / or a test device.

[0020] In this application, tire use of tire singular includes the plural, and tire words “a,” “an” and “the” mean “at least one” unless specifically stated otherwise. Furthermore, the use of the term “including,” as well as other forms such as “includes” and “included,” is not limiting. Also, terms such as “element” or “component” encompass both elements or components including one unit and elements or components that include more than one unit, unless specifically stated otherwise. As used herein, the conjunction “and” is intended to be inclusive and the conjunction “or” is not intended to be exclusive, unless otherwise indicated. For example, tire phrase “or, alternatively” is intended to be exclusive. As used herein, the termDocket No. P24-266-SEC-WO01“and / or” refers to any combination of the foregoing elements including using a single element.

[0021] As used herein, “about” or “approximately” is intended to correspond to ± 5% of the stated value.

[0022] “Substantially free” is defined herein as less than 2 wt. %, preferably less than 1 wt. %, more preferably less than 0.5 wt. %, and most preferably less than 0.1 wt. %. “Substantially free” also includes 0.0 wt. %. The term “free of’ means 0.0 wt. %.

[0023] “Substantially free” is defined herein as less than 2 wt. %, preferably less than 1 wt. %, more preferably less than 0.5 wt. %, and even more preferably less than 0.1 wt. %. The term “free of’ is defined herein as 0 wt. %.

[0024] As used herein, the term “halo” means halogen groups and includes, but is not limited to, fluoro, chloro, bromo and iodo.

[0025] The use of recesses and features in the context of describing the disclosed and claimed subject matter (especially in the context of the following claims) is interchangeable, both are referring to vias, gaps, or areas between fins in semiconductor substrates.

[0026] As used herein and in the claims, the terms “comprising,” “comprises,” “including,” and “includes” are inclusive or open-ended and do not exclude additional unrecited elements, composition components, or method steps. Accordingly, these terms encompass the more restrictive terms “consisting essentially of’ and “consisting of.” Unless specified otherwise, all values provided herein include up to and including the endpoints given, and the values of the constituents or components of the compositions are expressed in weight percent of each ingredient in the composition.

[0027] In compositions “consisting essentially of’ recited components, such components may add up to 100 weight % of the composition or may add up to less than 100 weight % (“wt.%”). Where the components add up to less than 100 weight %, such composition may include some small amounts of a non-essential contaminants or impurities. For example, in one such embodiment, the cleaning composition can contain 2% by weight or less of impurities. In another embodiment, the cleaning composition can contain 1% by weight or less than of impurities. In a further embodiment, the cleaning composition can contain 0.05% by weight or less than of impurities. In other such embodiments, the ingredients can form at least 90 wt.%, more preferably at least 95 wt.%, more preferably at least 99 wt.%, more preferably at least 99.5 wt.%, most preferably at least 99.9 wt.%, and can include other ingredients that do not material affect the performance of the cleaning compositions. Otherwise, if no significant non-essentialDocket No. P24-266-SEC-WO01 impurity component is present, it is understood that the combination of all essential constituent components will essentially add up to 100 wt. %.

[0028] In all such compositions, wherein specific components of the composition are discussed in reference to weight percentage ranges including a zero lower limit, it will be understood that such components may be present or absent in various specific embodiments of the composition, and that in instances where such components are present, they may be present at concentrations as low as 0.001 weight percent, based on the total weight of the composition in which such components are employed.

[0029] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplar / language (e.g., “such as”) provided herein, is intended merely to better illuminate the disclosed and claimed subject matter and does not pose a limitation on the scope of the disclosed and claimed subject matter unless otherwise claimed. No language in the specification should be construed as indicating any nonclaimed element as essential to the practice of the disclosed and claimed subject matter.

[0030] The section headings used herein are for organizational purposes and are not to be construed as limiting the subject matter described. All documents, or portions of documents, cited in this application, including, but not limited to, patents, patent applications, articles, books, and treatises, are hereby expressly incorporated herein by reference in their entirety for any purpose. In the event that any of the incorporated literature and similar materials defines a term in a manner that contradicts the definition of that term in this application, this application controls.DETAILED DESCRIPTION

[0031] It is to be understood that both the foregoing general description and the following detailed description are illustrative and explanatory, and are not restrictive of the subject matter, as claimed. The objects, features, advantages and ideas of the disclosed subject matter will be apparent to those skilled in the art from the description provided in the specification, and the disclosed subject matter will be readily practicable by those skilled in the art on the basis of the description appearing herein. The description of any “preferred embodiments” and / or the examples which show preferred modes for practicing the disclosed subject matter are included for the purpose of explanation and are not intended to limit the scope of the claims.

[0032] It will also be apparent to those skilled in the art that variousDocket No. P24-266-SEC-WO01 modifications may be made in how the disclosed subject matter is practiced based on described aspects in the specification without departing from the spirit and scope of the disclosed subject matter disclosed herein.

[0033] In the below-described embodiments directed to methods or processes, it is understood that in some embodiments the steps of the methods may be performed in a variety of orders, may be performed sequentially or concurrently (e.g., during at least a portion of another step), and any combination thereof. The respective step of supplying the precursors and the nitrogen-containing source gases may be performed by varying the duration of the time for supplying them to change the stoichiometric composition of the resulting dielectric film.

[0034] Preferred embodiments of the disclosed and claimed subject matter are described herein. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. It is expected that skilled artisans that the disclosed and claimed subject matter to be practiced otherwise than as specifically described herein. Accordingly, the disclosed and claimed subject matter includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosed and claimed subject matter unless otherwise indicated herein or otherwise clearly contradicted by context.

[0035] Described herein are compositions and methods related to the formation of a crystalline stoichiometric or nonstoichiometric film or material that includes boron, such as boron nitride with one or more temperatures, room temperature (e.g., about 25 °C) to about 1000 °C, or from room temperature to about 400 °C, or from room temperature to about 300 °C, or from room temperature to about 200 °C, or from room temperature to about 100 °C. The films described herein are deposited in a deposition process such as, a chemical vapor deposition (CVD) process, an atomic layer deposition (ALD) or in an ALD-like process, such as without limitation, a plasma enhanced ALD or a plasma enhanced cyclic chemical vapor deposition process (CCVD).

[0036] The disclosed and claimed subject matter provides a method to deposit crystalline boron nitride onto at least one surface of a substrate which includes, consists essentially of or consists of the steps of:(a) providing a substrate in a reactor;(b) providing to the at least one surface of the substrate a boron-containingDocket No. P24-266-SEC-WO01 precursor selected from a trialkylborane, borazine or a derivative thereof and a compound having the structure of Formula I:B(NR1R2)nX3.n (I), wherein R1is selected from a linear Ci to Cio alkyl group, a branched C3 to Cio alkyl group, a linear or branched C3 to Cio alkenyl group, a linear or branched C3 to Cio alkynyl group, a Ci to Ce dialkylamino group, an electron withdrawing group, and a C4 to Cio aryl group; R2is selected from hydrogen, a linear Ci to Cio alkyl group, a branched C3 to Cio alkyl group, a linear or branched C3 to Ce alkenyl group, a linear or branched C3 to Ce alkynyl group, a Ci to Ce dialkylamino group, a Ce to Cio aryl group, a linear or branched Ci to Ce fluorinated alkyl group, an electron withdrawing group, and a C4 to Cio aryl group; X is Cl, Br, I, or F; and n = 1 or 2, wherein R1and R2are optionally linked together to form a ring selected from a substituted or unsubstituted aromatic ring or a substituted or unsubstituted aliphatic ring, and wherein R1and R2may be the same moiety or different moieties;(c) purging the reactor with a purge gas;(d) providing to the at least one surface of the substrate a nitrogencontaining source;(e) purging the reactor with a purge gas;(f) introducing into the reactor at least an inert ICP gas plasma such as argon under constant or selective DC or RF bias applied on the substrate side; and(g) purging the reactor with a purge gas.

[0037] Steps b through g are repeated until a desired thickness of the crystalline boron nitride film. In one aspect of this embodiment, the crystalline boron nitride film is deposited using a deposition process selected from chemical vapor deposition and atomic layer deposition.

[0038] Examples of boron-containing precursors that can be used in step (b) having a chemical structure represented by Formula I include, but are not limited to bis(dimethylamino)chloroborane, bis(dimethylamino)bromoborane, bis(dimethylamino)iodoborane, bis(diethylamino)chloroborane, bis(diethylamino)bromoborane, bis(diethylamino)iodoborane, bis(ethylmethylamino)chloroborane, bis(ethylmethylamino)bromoborane, bis(ethylmethylamino)iodoborane, (di-iso-propylamino)dichloroborane, (di-iso- propylamino)dibromoborane, (di-iso-propylamino)diiodoborane(pyrrolidino)chloroborane, (pyrrolidino)bromoborane, (pyrrolidino)iodoborane, (2-Docket No. P24-266-SEC-WO01 methyl-pyrrolidino)chloroborane, (2-methyl-pyrrolidino)bromoborane, (2-methyl- pyrrolidino)iodoborane, (2,5-dimethyl-pynolidino)chloroborane, (2,5-dimethyl- pyrrolidino)bromoborane, (2,5dimethyl-pyrrolidino)iodoborane(piperidino)chloroborane, (piperidino)bromoborane, (piperidino)iodoborane, (2,6- dimethyl-piperidino)dichloroborane, (2,6-dimethyl-piperidino)dibromoborane, and (2,6-dimethyl-piperidino)diiodoborane. A preferred boron-containing precursor is bis(dimethylamino)bromoborane or bis(ethylmethylamino)bromoborane.

[0039] In one embodiment, the boron-containing precursor is a trialkylborane. In one aspect of this embodiment, the tri alkylborane includes, consists essentially of or consists of a triethylborane. In one embodiment, the boron-containing precursor includes, consists essentially of or consists of a tris(alkylamino)borane. In one embodiment, the boron-containing precursor includes, consists essentially of or consists of borazine or a derivative thereof (e.g., a singly or multi -halogenated borazine). In another aspect of this embodiment, the boron-containing precursor includes, consists essentially of or consists of 2,4,6-trichloroborazine, tris(diethylamino)borazine and tris(dimethylamino)borane.

[0040] The step (1 inert gas plasma can be selected from group of argon, krypton, and combination thereof. Without being bound by theory, it is believed these types of heavy ions help formation of crystalline boron nitride films.

[0041] The step (d) nitrogen-containing source may be introduced into the reactor in the form of at least one nitrogen source and / or may be present incidentally in the other precursors used in the deposition process. Suitable nitrogen-containing source gases may include, for example, ammonia organoamine (e.g., methylamine, dimethylamine, ethylamine, diethylamine, tert-butylamine), organoamine plasma, nitrogen, nitrogen plasma, nitrogen / hydrogen, nitrogen / helium, nitrogen / argon plasma, ammonia plasma, ammonia / helium plasma, ammonia / argon plasma, ammonia / nitrogen plasma, NF3, NF3 plasma, and mixtures thereof. In one embodiment, the nitrogen-containing sources are nitrogen or amine radicals from a plasma such as NH, NH2, or N.

[0042] The respective steps of supplying the boron-containing precursors and / or other precursors, source gases, and / or reagents may be performed by changing the time for supplying them to change the stoichiometric composition of the resulting film.

[0043] Energy is applied to the at least one of the precursors, nitrogen containing source, or combination thereof to induce reaction and to form the film or coating on the substrate. Such energy can be provided by, but not limited to, thermal, plasma, pulsedDocket No. P24-266-SEC-WO01 plasma, helicon plasma, high density plasma, inductively coupled plasma, X-ray, e-beam, photon, remote plasma methods, and combinations thereof. In certain embodiments, a secondary RF frequency source can be used to modify the plasma characteristics at the substrate surface. In embodiments wherein the deposition involves plasma, the plasmagenerated process may comprise a direct plasma-generated process in which plasma is directly generated in the reactor, or alternatively, a remote plasma-generated process in which plasma is generated outside of the reactor and supplied into the reactor.

[0044] The at least one precursor may be delivered to the reaction chamber such as a plasma enhanced cyclic CVD or PEALD reactor or a batch furnace type reactor in a variety of ways. In one embodiment, a liquid delivery system may be utilized. In an alternative embodiment, a combined liquid delivery and flash vaporization process unit may be employed, such as, for example, the turbo vaporizer manufactured by MSP Corporation of Shoreview, MN, to enable low volatility materials to be volumetrically delivered, which leads to reproducible transport and deposition without thermal decomposition of the precursor. In liquid delivery formulations, the precursors described herein may be delivered in neat liquid form, or alternatively, may be employed in solvent formulations or compositions comprising same. Thus, in certain embodiments the precursor formulations may include solvent component(s) of suitable character as may be desirable and advantageous in a given end use application to form a film on a substrate.

[0045] As previously mentioned, the purity level of the boron-containing precursor is sufficiently high enough to be acceptable for reliable semiconductor manufacturing. In certain embodiments, the precursor described herein comprise less than 2% by weight, or less than 1% by weight, or less than 0.5% by weight of one or more of the following impurities: free amines, free halides or halogen ions, and higher molecular weight species. Higher purity levels of the precursor described herein can be obtained through one or more of the following processes: purification, adsorption, and / or distillation.

[0046] In one embodiment of the method described herein, a plasma enhanced cyclic deposition process such as PEALD-like or PEALD may be used wherein the deposition is conducted using the precursor(s) and nitrogen-containing source. The PEALD-like process is defined as a plasma enhanced cyclic CVD process but still provides high conformal boron-containing films.

[0047] In certain embodiments, the gas lines connecting from the precursor canisters to the reaction chamber are heated to one or more temperatures depending upon the process requirements and the container of the precursor is kept at one or moreDocket No. P24-266-SEC-WO01 temperatures for bubbling. In other embodiments, a solution comprising the precursor is injected into a vaporizer kept at one or more temperatures for direct liquid injection.

[0048] A flow of argon and / or other gas may be employed as a carrier gas to help deliver the vapor of the at least one boron-containing precursor to the reaction chamber during the precursor pulsing. In certain embodiments, the reaction chamber process pressure is about 3 mTorr to 20 mTorr or about 5 mTorr to 10 mTorr. In other embodiments, the reaction chamber process pressure can be up to 760 Torr.

[0049] In a typical PEALD or a PEALD-like process such as a PECVD process, the substrate such as a silicon oxide substrate is heated on a heater stage in a reaction chamber that is exposed to the precursor initially to allow the complex to chemically adsorb onto the surface of the substrate.

[0050] As previously mentioned, a purge gas such as argon purges away unabsorbed excess complex from the process chamber. After sufficient purging, the nitrogen source may be introduced into reaction chamber to react with the absorbed surface followed by another gas purge to remove reaction by-products from the chamber. The process cycle can be repeated to achieve the desired film thickness. In some cases, pumping can replace a purge with inert gas, or both can be employed to remove unreacted precursors.

[0051] In this or other embodiments, it is understood that the steps of the methods described herein may be performed in a variety of orders, may be performed sequentially, may be performed concurrently (e.g., during at least a portion of another step), and any combination thereof. The respective step of supplying the precursors and the nitrogen-containing source gases may be performed by varying the duration of the time for supplying them to change the stoichiometric composition of the resulting dielectric film. Also, purge times after precursor or nitrogen-containing steps can be minimized to < 0.1 seconds so that throughput can be improved.

[0052] Various commercial ALD reactors such as single wafer, semi-batch, batch furnace or roll to roll reactor can be employed for depositing the boron-containing film or materials described herein.

[0053] Process temperature for the method described herein use one or more of the following temperatures (°C) as endpoints: 0, 25, 50, 75, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425, 450, 500, 525, 550, 575, 600. Exemplary temperature ranges include, but are not limited to the following: from about 0 °C to about 600 °C; or from about 25 °C to about 500 °C; or from about 150 °C to about 400 °C; or from about 25 °C to about 300 °C, or from about 25 °C to about 200 °C.Docket No. P24-266-SEC-WO01

[0054] As mentioned previously, the method described herein may be used to deposit a boron-containing film on at least a portion of a substrate. Examples of suitable substrates include but are not limited to, silicon, SiO . SisNa, OSG, FSG, silicon carbide, hydrogenated silicon carbide, silicon nitride, hydrogenated silicon nitride, silicon carbonitride, hydrogenated silicon carbonitride, boronitride, aluminum nitride, antireflective coatings, photoresists, germanium, germanium-containing, boron- containing, Ga / As, a flexible substrate, organic polymers, porous organic and inorganic materials, metals such as copper and aluminum, and diffusion barrier layers such as but not limited to TiN, Ti(C)N, TaN, Ta(C)N, Ta, W, or WN. The films are compatible with a variety of subsequent processing steps such as, for example, chemical mechanical planarization (CMP) and anisotropic etching processes.

[0055] The features and advantages are more fully shown by the illustrative examples discussed below.Examples

[0056] Reference will now be made to more specific embodiments of the present disclosure and experimental results that provide support for such embodiments. The examples given below more fully illustrate the disclosed and claimed subject matter and should not be construed as limiting the disclosed subject matter in any way.

[0057] It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed subject matter and specific examples provided herein without departing from the spirit or scope of the disclosed subject matter. Thus, it is intended that the disclosed subject matter, including the descriptions provided by the following examples, covers the modifications and variations of the disclosed subject matter that come within the scope of any claims and their equivalents.

[0058] In the following examples, unless stated otherwise, properties were obtained from sample films that were deposited onto medium resistivity (14-17 S2-cm) single crystal silicon wafer substrates. All film depositions were performed using an ALD tool custom built with in-situ XPS and plasma capability the chamber pressure was fixed at a pressure ranging from about 5 to 10 mTorr. Additional inert gas such as argon or nitrogen was used to maintain chamber pressure. The organoborane precursor was delivered by bubbling 50 seem Argon through the vessel while the vessel is held at 50 °C. Typical RF power used was 0-300 W.

[0059] The refractive index (RI) and thickness for the deposited films were measured either using an ellipsometer (e.g., Ellipso Technology's model Elli-SE-Docket No. P24-266-SEC-WO01UaM12 at room temperature) or transmission electron microscopy (JEOL's HRTEM, model JEM-3010). Film composition was analyzed using in situ x-ray photoelectron spectroscopy (XPS. Film crystallinity and thickness was measured by XRD using (Rigaku Corp, model SmartLab). Film surface roughness was measured by atomic force microscopy (AFM using (XE-150, Park systems). All measurements were conducted in accordance with conventional methods.

[0060] The BN ALD film was deposited on Si (100) in a custom-built vacuum chamber. The chamber was connected to a downstream inductively coupled plasma (ICP) source (PIE Scientific Semi-KLEEN Sapphire Plasma) and featured a stage with direct cunent (DC) biasing capabilities. Boron nitride (BN) was deposited. bis(dimethylamino)bromoborane was heated to 0 to 75 °C prior to deposition. The atomic layer annealing process cycle for bis(dimethylamino)bromoborane and ammonia plasma consisted of four main steps: three consecutive sets of 100 ms bis(dimethylamino)bromoborane followed by a 3.5s purge, a4-second delay before igniting the Ar plasma, 8 seconds of dosing ammonia into the plasma, 14 seconds of argon ion bombardment, and a final 7-second purge, as illustrated in FIG. 1 wherein BBB precursor is bis(dimethylamino)bromoborane. Notably, since the ionization rate of ammonia is lower than that of argon, a sequence of alternating flows was applied — 0.4 seconds of ammonia followed by 0.6 seconds of argon — to stabilize the ammonia plasma. The deposition was conducted at a substrate temperature of 350 °C and a chamber wall temperature of 90 °C. A continuous or intermittent bias of -25 V was employed on the substrate side.

[0061] The high-resolution TEM, as shown in FIG. 2 reveals the crystal structure of the proposed ALA BN on the Si (100) substrate. The d-spacing between each lattice fringe is 0.33 nm, which is consistent with the planar spacing of hexagonal BN. Notably, the clear h-BN / SiO2 interface demonstrates the potential of a thermal interface material, as it reduces phonon scattering at the interface. FIG. 3 shows the electron energy loss spectrum (EELS analysis), which is sensitive to light elements such as boron. The peaks at 190 eV, 284 eV, 399 eV, and 540 eV correspond to elemental boron, carbon, nitrogen, and oxygen, respectively. The spectrum identifies the film as a boron nitride film. Moreover, the quantitative chemical analysis in Table 1 shows that the boron-to-nitrogen ratio is nearly one-to-one in the film, indicating that the film produced via this atomic layer annealing process is stoichiometric. The carbon content of less than 1 % indicates that the amino ligands are completely exchanged and purged. The spectrum in FIG. 3 also provides details about the electronic structure of theDocket No. P24-266-SEC-WO01 deposited BN. The near-edge electron loss of the boron element, ranging from 190 eV to 205 eV in the spectrum, includes electron transitions between molecular orbitals. The absorption edges at 192 eV and 197 eV represent the K and o bonds in the BN film, respectively. The near-edge electron loss signal confirms the existence of it bonds in our ALA BN, indicating the presence of the h-BN phase in the film. Table 2 shows The ballistic phonon transport, where the effective thermal boundary conductance (TBC) remains independent of film thickness has been observed in boht AIN and BN film < 60 nm.

[0062] The ALA methodology was designed to investigate how BBDMAB, TEB, and TCB precursors interact with ammonia plasma and subsequent argon annealing. Each ALA cycle consisted of a precursor dosing step (variant), Ar purge (3 seconds), ammonia plasma exposure, argon plasma annealing, and a final purge, as shown in Figs.4 (a) to (c). The ammonia plasma was pulsed for a total of 8 s (25 W ICP downstream plasma (PIE Corp), with background Ar 10 mTorr) using 450 ms on / 550 ms off intervals ammonia dosing (plasma keep on in 8 seconds), followed by a 14 s pure Ar downstream plasma anneal under the same power and pressure during which a negative bias (typically -25V was applied to the substrate). Purge times between steps were maintained at 7 s. Each boron precursor dosing step comprised three sub-pulses separated by 3 s intervals to ensure surface saturation, as shown in Figs. 4 (a-c). All the precursor dosing steps had a 10 mTorr Ar background / carrier gas. Because of the vapor pressure difference, the three precursors had different pulsing lengths. For BBDMAB, as shown in Fig. 4(a), each sub-pulse was 100 ms in duration. For TEB, as shown in Fig. 4(b), each sub-pulse was 50 ms in duration, while for TCB a longer 250 ms subpulse was used to compensate for its lower vapor pressure (2 torr at room temperature). Depositions using BBDMAB and TCB were carried out at 350 °C, whereas TEB processes were conducted at 400 °C. Note, TEB is not an ALD process but instead a pulsed CVD process, as shown in Fig. 15.

[0063] For substrate preparation, Si (100) wafers with a resistivity of <0.005 Q-cm were used in this study. The samples used for growth-per-cycle (GPC) measurements underwent standard solvent cleaning, including sequential degreasing in acetone, isopropanol, and deionized water. For TEM, thermal, and electrical studies, the substrates were additionally cleaned using a 2% HF solution for 2 minutes to remove native S1O2 and minimize interfacial defects.Docket No. P24-266-SEC-WO01

[0064] To qualitatively evaluate the performance of boron nitride films deposited using TCB, BBDMAB, and TEB under the designated ALA process, nanobeam electron diffraction (NBD) and in-situ X-ray photoelectron spectroscopy (XPS) analyses were performed on 30 nm films grown on Si (100) substrates using the ALA process with each of the three precursors. Figures. 5(a-c) show the NBD patterns of the 30 nm films deposited using TCB, BBDMAB, and TEB under the optimized ALA conditions described in Figure 4, employing a 25 W 1CP downstream plasma (PIE Corp) and a substrate bias -25 V during Ar plasma anneal step. All three films exhibit the h-BN (002) diffraction reflection, confirming the formation of crystalline hexagonal BN. The relative intensity ratio of the (002) to (100) diffraction peaks — where the (002) reflection appears as a diffraction spot (indicating preferred orientation) and the (100) reflection appears as a ring (indicating random orientation) in Figures 5(a-c) — was used to assess the degree of c-axis texture in the films. As shown in Figure 5(d), the TCB- derived film exhibits a (002) / (100) intensity ratio of 3.51, indicating a higher fraction of BN domains aligned along the (002) orientation compared to the BBDMAB- and TEB-derived films, which exhibit ratios of approximately 1.5. However, due to the complex nature of electron diffraction and the limitations of cross-plane scanning, the absolute intensity ratio does not directly represent the quantitative proportion of (002) and (100) grains within the film. The enhanced (002) texture in the TCB-derived film is attributed to the chemical characteristics of the TCB precursor, which contains highly volatile chlorine ligands and lacks carbon-containing groups, thereby enabling more efficient ligand removal during the ALA process.

[0065] In contrast to TCB, the carbon-containing ligands in BBDMAB and TEB increase the likelihood of carbon incorporation during film growth. This interpretation is supported by the in-situ XPS spectra shown in Figure 5(e), where approximately 10 at.% carbon is detected in the BBDMAB- and TEB-derived films, while the TCB-derived film shows negligible carbon (<1 at.%). Furthermore, the chlorine concentration in the TCB-derived film is below 2 at.%, indicating that residual chlorine was effectively removed during ammonia plasma exposure. These results collectively demonstrate that ligand composition strongly influences BN film purity and texture, with TCB providing the most favorable chemical and structural characteristics among the three precursors.

[0066] To further assess the reactivity and self-limiting behavior of TCB — the most promising precursor — a saturation study was conducted to determine its optimalDocket No. P24-266-SEC-WO01ALD temperature window and steady-state growth regime in the ALA process, where the -25 V Ar plasma was implemented after mixed ammonia + Ar reactive plasma exposure. The substrate temperature dependence of growth for the TCB precursor was examined, as shown in FIG. 4(a). The growth per cycle (GPC) of TCB was approximately 0.4 A cycle ' within the temperature range of 300-400 °C, implying that TCB chemisorbs stably on the Si (100) surface within this thermal window. FIG. 4(b) and FIG. 4(c) show the TCB + ammonia plasma reaction (25 W, Ar and Ammonia mixture plasma) is a self-limiting reaction with respect to the NFL plasma dose and the TCB dose, where the GPC is constant regardless of the exposure of ammonia time between 8 to 20 seconds or overexposure of TCB precursor (500 to 1250 ms). Note that each TCB half cycle was composed of 3 equal sub cycles (250 ms with 3 s purge time). These results confirm that TCB enables a self-limiting, ALA process within 300-400 °C, providing a stable baseline for subsequent electrical characterization at varied temperatures. In the following experiments, PEALD with and without additional substrate bias with 8 seconds ammonia plasma and 750 ms TCB pulsing at 350 °C was employed to study substrate bias impact on leakage current and microstructure.

[0067] The following experiments compare PEALD BN and ALA BN films deposited at 350 °C to evaluate the influence of an additional Ar annealing step applied after the ammonia exposure.

[0068] In the HRTEM image of the PEALD film with no external substrate bias shown in FIGs. 5(a) and 5(b), lattice fringes with a spacing of approximately 3.3 A were observed, corresponding to the (002) planes of h-BN. However, more than 50% of the film area did not exhibit lattice fringes, indicating that a large portion of the BN film is amorphous. Furthermore, the h-BN nanocrystals observed in the film were randomly oriented, suggesting the absence of preferred texture. The corresponding diffraction pattern (inset of FIGs. 5(a)-(b)) supports the HRTEM observations, confirming the lack of a well-defined crystalline phase in the film.

[0069] FIG. 6(a) and FIG. 6(c), corresponding to depositions carried out at 350 °C, demonstrate that the ALA process of boron nitride with -25 V substrate bias using BBDMAB and ammonia exhibits a clear self-limiting growth behavior. Under identical deposition conditions, the GPC remains 0.3 A cycle indicating that film growth is independent of precursor exposure time and reactant concentration.

[0070] Similarly, as shown in FIG. 6(b), the GPC of the deposition reaction remains constant at approximately 0.3 A cycle1across the temperature range of 300-Docket No. P24-266-SEC-WO01430 °C, confirming that BBDMAB chemisorbs on the substrate surface and reacts efficiently with ammonia within this thermal window. The invariance of GPC with temperature confirms a surface-saturated ALD regime dominated by self-limiting surface reactions rather than gas-phase or transport-limited kinetics.

[0071] Moreover, the effect of additional plasma annealing, shown in FIG. 6(d), reveals that a -25 V substrate bias (=25 eV Ar+energy) does not alter the GPC regardless of plasma exposure time. This indicates that Ar-ion bombardment has a negligible influence on the surface reaction kinetics of the ALD process and primarily affects the film microstructure — specifically, the defect density, crystallinity, and atomic ordering of the deposited BN.TABLE 1. The EELS Element Quantification of BN Through Harte-Sarte Model by Software GMS 3.0TABLE 2. The ballistic heat transport behavior of the ALA BN filmDocket No. P24-266-SEC-WO01

[0072] Although the disclosed and claimed subject matter has been described and illustrated with a certain degree of particularity, it is understood that the disclosure has been made only by way of example, and that numerous changes in the conditions and order of steps can be resorted to by those skilled in the art without departing from the spirit and scope of the disclosed and claimed subject matter.

Claims

Docket No. P24-266-SEC-WO01CLAIMSWhat is claimed is:

1. A method to deposit crystalline boron nitride onto at least one surface of a substrate which includes, consists essentially of or consists of the steps of:(a) providing a substrate in a reactor;(b) providing to the at least one surface of the substrate a boron-containing precursor selected from a trialkylborane, borazine or a derivative thereof and a compound having the structure of Formula I:B NR^nXj-z, (I), wherein R1is selected from a linear Ci to Cio alkyl group, a branched C3 to Cio alkyl group, a linear or branched C3 to Cio alkenyl group, a linear or branched C3 to Cio alkynyl group, a Ci to C& dialkylamino group, an electron withdrawing group, and a C4 to Cio aryl group; R2is selected from hydrogen, a linear Ci to Cio alkyl group, a branched C3 to Cio alkyl group, a linear or branched C3 to Ce alkenyl group, a linear or branched C3 to Ce alkynyl group, a Ci to Ce dialkylamino group, a Ce to Cio aryl group, a linear or branched Ci to Ce fluorinated alkyl group, an electron withdrawing group, and a C4 to Cio aryl group; X is Cl, Br, I, or F; and n = 1 or 2, wherein R1and R2are optionally linked together to form a ring selected from a substituted or unsubstituted aromatic ring or a substituted or unsubstituted aliphatic ring, and wherein R1and R2may be the same moiety or different moieties:(c) purging the reactor with a purge gas;(d) providing to the at least one surface of the substrate a nitrogen-containing source;(e) purging the reactor with a purge gas;(f) introducing into the reactor at least an inert ICP gas plasma such as argon under constant or selective DC or RF bias applied on the substrate side; and(g) purging the reactor with a purge gas.

2. The method of claim 1, wherein R1and R2are linked together to form a ring.

3. The method of claim 1, wherein R1and R2are selected from a linear or a branched C3 to Ce alkyl group and are linked to form a ring.

4. The method of claim 1, wherein R1and R2are not linked together to form a ring.Docket No. P24-266-SEC-WO015. The method of claim 1 , wherein R1and R2are different.

6. The method of claim 1 wherein R1and R2are the same.

7. The method of claim 1 , wherein the boron-containing precursor is selected from the group of bis(dimethylamino)chloroborane, bis(dimethylamino)bromoborane, bis(dimethylamino)iodoborane, bis(diethylamino)chloroborane, bis(diethylamino)bromoborane, bis(diethylamino)iodoborane, bis(ethylmethylamino)chloroborane, bis(ethylmethylamino)bromoborane, bis(ethylmethylamino)iodoborane: (di-iso-propylamino)dichloroborane, (di-iso- propylamino)dibromoborane, (di-iso-propylamino)diiodoborane(pyrrolidino)chloroborane, (pyrrolidino)bromoborane, (pyrrolidino)iodoborane, (2- methyl-pyrrolidino)chloroborane, (2-methyl-pyrrolidino)bromoborane, (2-methyl- pyrrolidino)iodoborane, (piperidino)chloroborane, (piperidino)bromoborane, (piperidino)iodoborane, (2,6-dimethyl-piperidino)dichloroborane, (2,6-dimethyl- piperidino)dibromoborane, and (2,6-dimethyl-piperidino)diiodoborane.

8. The method of claim 1, wherein the boron-containing precursor comprises bis(dimethylamino)bromoborane.

9. The method of claim 1 , wherein the boron-containing precursor is selected from the group of a trialkylborane, and a tris(alkylamino)borane.

10. The method of claim 1 , wherein the boron-containing precursor is selected from the group of triethylborane, 2,4,6-trichloroborazine, tris(diethylamino)borazine, and tris(dimethylamino)borane.

11. The method of claim 1, wherein the boron-containing precursor comprises trichloroborazine.

12. The method of claim 1, wherein the boron nitride film comprises hexagonal boron nitride.Docket No. P24-266-SEC-WO0113. The method of claim 1, wherein the boron nitride film comprises hexagonal boron nitride and is vertically aligned h-BN structures.

14. A method for forming a crystalline hexagonal boron nitride (h-BN) thin film at a temperature 400 °C or lower, comprising:(a) providing a substrate within a vacuum deposition chamber;(b) exposing the substrate surface to a boron precursor selected from the group consisting of bromobis(dimethylamino)borane (BBDMAB), triethylborane (TEB), and trichloroborazine (TCB) under atomic layer annealing (ALA) or plasma-enhanced atomic layer deposition (PEALD) conditions;(c) purging the chamber with an inert gas;(d) exposing the substrate to an ammonia-containing plasma to form a boron nitride film on the substrate surface; and(e) applying a plasma annealing step comprising exposure to an argon plasma under a substrate bias between -15 V and -35 V, thereby inducing ion bombardment sufficient to crystallize the boron nitride film into a vertically aligned hexagonal phase; wherein the process produces a film having a leakage current density below 106A cm2at 1 MV cm1and exhibiting cross-plane ballistic phonon transport characterized by an effective thermal boundary conductance greater than 150 MW m2K15. The method of claim 14, wherein the substrate temperature is maintained between 300 °C and 400 °C.

16. The method of claim 14, wherein the boron precursor is trichloroborazine (TCB).

17. The method of claim 14, wherein the argon plasma annealing step immediately follows the ammonia plasma exposure.

18. The method of claim 14, wherein the resulting h-BN film comprises vertically aligned (002) domains with a (002) / (100) diffraction intensity ratio 1 to 3.

19. The method of claim 14, wherein the film exhibits an effective dielectric constant of about 4 or less.Docket No. P24-266-SEC-WO0120. The method of claim 14, wherein the process yields a ballistic transport regime with thickness-independent thermal boundary conductance over a range of 20-60 nm film thickness.

21. A method for enhancing the crystallinity of boron nitride thin films formed by plasma-enhanced atomic layer deposition, comprising applying an argon-ion atomic layer annealing step at a substrate bias of about -25 V immediately after each ammonia plasma exposure, thereby converting amorphous boron nitride to vertically aligned hexagonal boron nitride with improved dielectric and thermal performance.

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