Patent Application
20240052493
The present inventive concept relates to methods of depositing layers and enhancement of methods of preparing thick films, such as metal nitride films.
Aluminum nitride (AlN) is a promising material due to its high thermal conductivity and close lattice match to gallium nitride (GaN) and indium gallium nitride (InGaN). Accordingly, AlN can have application as a heat spreading material, as a buffer layer material, and/or as a template layer material. Deposition methods that provide crystalline aluminum nitride typically require temperatures exceeding 800° C., such as metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE); this presents barriers to integration in back-end-of-line (BEOL) processing. For application of AlN as a buffer layer for the growth of GaN and InGaN on silicon (Si) and silicon carbide (SiC), high-quality crystalline AlN films with c-axis orientation are necessary. Deposition methods at comparatively lower temperatures (˜350° C.), such as plasma-enhanced ALD (PE-ALD) and atomic layer annealing (ALA), can be used to deposit crystalline or polycrystalline AlN with less strain than films deposited at higher temperatures; however, PE-ALD produces non-stoichiometric AlN films that are often nano-crystalline. Atomic layer annealing has recently drawn attention for low temperature deposition of crystalline or polycrystalline AlN, however its practical utility is limited by low deposition rates due to lengthy ion bombardment treatments and the relative complexity of required deposition tools.
Accordingly, improved methods for preparing thin films, such as for use as a heat spreading material, a templating layer, and/or a buffering layer, as well as for use in preparing III-IV semiconductors on, for example, silicon or silicon carbide (SiC), for use in electronic devices, such as radio frequency, power, and/or microLED devices, are needed.
This present inventive concept is related to a method for formation of high-quality, metal nitride films for applications as a buffer layer and/or template layer. AlN has the advantage of being both a good conductor of heat as well as an electrical insulator and as such it is of great interest for use as a heat spreading material in RF circuits as well in 3D heterogeneous integration (packaging) of logic and/or memory devices. Using either trimethyl aluminum (TMA) and hydrazine (N2H4) or tris(dimethylamido) aluminum (TDMAA) (or related compounds such as tris(diethylamido) aluminum) and N2H4, high-quality AlN films are deposited with large grain size and low oxygen/carbon contamination can be used as a templating layer for further film growth. As heat spreading layers often need to be in excess of 1 μm thick, film growth of a template layer through pulsed chemical vapor deposition (CVD) of TDMAA and N2H4 at <580° C., followed by further film growth through sputter deposition, to yield high quality metal nitride polycrystalline films, such as AlN, GaN, or InGaN sputtered on an AlN template layer, are encompassed by aspects of the present inventive concept.
Accordingly, in an aspect of the present inventive concept, provided is a method of preparing a thin film layer comprising at least one cycle of: exposing a surface of a substrate to an organometallic chemical precursor; and exposing the organometallic chemical precursor to a nitrogen-containing co-reactant to provide a metal nitride layer on the substrate, wherein the at least one cycle is performed at a temperature at or less than about 580° C., or less than about 400° C.
In another aspect of the present inventive concept, provided is a method of preparing a crystalline metal nitride layer comprising at least one cycle of: exposing a surface of a substrate to an organometallic chemical precursor; and exposing the organometallic chemical precursor to a nitrogen-containing co-reactant to provide a metal nitride template layer on the substrate, followed by: depositing a second metal nitride layer on the template layer to provide the crystalline metal nitride layer, wherein the at least one cycle is performed at a temperature at or less than about 580° C., or less than about 400° C.
In another aspect of the inventive concept, provided is a method of preparing a crystalline metal nitride layer comprising at least one cycle of: exposing a surface of a Si or SiC substrate to an TDMAA or TDEAA chemical precursor; and exposing the organometallic chemical precursor to a N2H4 co-reactant to provide an AlN template layer on the substrate, followed by, depositing a an AlN, GaN, or InGaN layer on the template layer to provide the crystalline metal nitride layer, wherein the at least one cycle comprises pulsed CVD, wherein the at least one cycle is performed at a temperature at or less than about 580° C., and wherein deposition of the AlN, GaN, or InGaN layer comprises sputtering.
Throughout the drawings, reference numbers can be re-used to indicate correspondence between referenced elements. The drawings are provided to illustrate embodiments of the present disclosure and do not to limit the scope thereof.
The foregoing and other aspects of the present invention will now be described in more detail with respect to other embodiments described herein. It should be appreciated that the invention can be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the description of the invention and the appended claims, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Additionally, as used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items and may be abbreviated as “/”.
The term “comprise,” as used herein, in addition to its regular meaning, may also include, and, in some embodiments, may specifically refer to the expressions “consist essentially of” and/or “consist of” Thus, the expression “comprise” can also refer to, in some embodiments, the specifically listed elements of that which is claimed and does not include further elements, as well as embodiments in which the specifically listed elements of that which is claimed may and/or does encompass further elements, or embodiments in which the specifically listed elements of that which is claimed may encompass further elements that do not materially affect the basic and novel characteristic(s) of that which is claimed. For example, that which is claimed, such as a composition, formulation, method, system, etc. “comprising” listed elements also encompasses, for example, a composition, formulation, method, kit, etc. “consisting of,” i.e., wherein that which is claimed does not include further elements, and a composition, formulation, method, kit, etc. “consisting essentially of,” i.e., wherein that which is claimed may include further elements that do not materially affect the basic and novel characteristic(s) of that which is claimed.
The term “about” generally refers to a range of numeric values that one of skill in the art would consider equivalent to the recited numeric value or having the same function or result. For example, “about” may refer to a range that is within ±1%, ±2%, ±5%, ±10%, ±15%, or even ±20% of the indicated value, depending upon the numeric values that one of skill in the art would consider equivalent to the recited numeric value or having the same function or result. Furthermore, in some embodiments, a numeric value modified by the term “about” may also include a numeric value that is “exactly” the recited numeric value. In addition, any numeric value presented without modification will be appreciated to include numeric values “about” the recited numeric value, as well as include “exactly” the recited numeric value. Similarly, the term “substantially” means largely, but not wholly, the same form, manner or degree and the particular element will have a range of configurations as a person of ordinary skill in the art would consider as having the same function or result. When a particular element is expressed as an approximation by use of the term “substantially,” it will be understood that the particular element forms another embodiment.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
This inventive concept allows for the deposition of aluminum nitride thin films for applications as heat spreader films, buffer layers, and/or templating films, that, in some embodiments, greatly enhance the quality of additional metal nitride, such as aluminum nitride, deposited by alternate deposition techniques and can reduce the overall thickness of needed buffer layers. Furthermore, these buffer and/or templating films/layers can be deposited at substrate temperatures of, for example, about 350° C., 400° C., about 450° C., about 500° C., about 550° C., and/or 580° C., which is considerably lower than other techniques, such as molecular beam epitaxy (MBE) and metal organic chemical vapor deposition (MOCVD), and include use of, for example, an AlN film, or in the alternative, a GaN, film and/or an InN film deposited on a substrate by, for example, chemical vapor deposition (CVD), such as pulsed CVD, or atomic layer annealing (ALA) as a buffer/template layer for further crystalline film growth thereon by, for example, sputtering, in the fabrication of films/layers.
The term “substrate,” as used herein, can broadly refer to any layer and/or surface upon which processing is desired. Thus, for example, a native oxide film on the surface of a silicon substrate may itself be considered a substrate for the purposes of this discussion. Likewise, layers deposited on silicon or on other base substrates may likewise be considered substrates in some embodiments. For example, in some embodiments, a multi-layer stack may be formed, and then atomic layer deposition and/or atomic layer annealing may be performed on the top layer, or a surface of the top layer, of the stack. In such a case, the top layer may be considered the substrate. In general, the layer or layers upon which the chemical precursor is deposited and/or which reacts with the chemical precursor can be considered the substrate layer(s). The material for the substrate may be any that may be appreciated by one of skill in the art in the field of electronics and/or semiconductors. In some embodiments, materials for the substrate include, for example, Si, and/or SiC. In some embodiments, the SiC may be 4H—SiC. In some embodiments, the SiC may be 6H—SiC.
The substrate, according to some embodiments, may include, but is not limited to, wafers. The wafers may be of various suitable processing sizes. For example, substrate samples may be on the order of 1 inch or smaller, if desired. Additionally, full wafers of about 200 mm or about 300 mm in diameter, or even larger substrates may be incorporated.
The term “chemical vapor deposition (CVD),” “atomic layer annealing” (ALA), and “atomic layer deposition” (ALD), as used herein, can broadly refer to the level of layer dimensional control that can be achieved at the angstrom (A) level. Thus, atomic layer deposition may generally correspond to the size of atoms and/or molecules. The average added layer thickness per cycle of CVD/ALA/ALD can be less than 1 Å (0.1 nm) per deposition cycle, for example, about 0.5 Å, about 0.6 Å, about 0.7 Å, about 0.8 Å, about 0.9 Å, about 1 Å, or more than 1 Å, for example, about 1.1 Å, about 1.2 Å, about 1.3 Å, about 1.4 Å, about 1.5 Å, about 2 Å, about 2.5 Å, about 3 Å, about 4 Å, about 5 Å, about 6 Å, about 7 Å, about 8 Å, about 9 Å, about 10 Å (1 nm), or any number between about 0.1-30 Å per deposition cycle. In some embodiments, the average added layer thickness per cycle is between about 0.1-4 Å, about 0.5-4 Å per deposition cycle, about 0.6-4 Å, about 0.7-4 Å per deposition cycle, about 0.8-4 Å per deposition cycle, about 0.9-4 Å per deposition cycle, about 1-4 Å per deposition cycle, about 1-2 Å per deposition cycle, about 1-1.5 Å per deposition cycle, or about 1.2-1.5 Å per deposition cycle. Similarly, the number of deposition cycles in the pulsed CVD/ALA/ALD process is not particularly limited, and may be any number of cycles that would be appreciated by one of skill in the art. For example, the number of deposition cycles in the process may be between 1 and about 1,000 cycles. In some embodiments, the number of deposition cycles may be between about 1-600 cycles, for example, 1 cycle, about 5 cycles, about 10 cycles, about 20 cycles, about 30 cycles, about 40 cycles, about 50 cycles, about 75 cycles, about 100 cycles, about 150 cycles, about 200 cycles, about 250 cycles, about 300 cycles, about 350 cycles, about 400 cycles, about 450 cycles, about 500 cycles, about 550 cycles, or about 600 cycles, or any number of deposition cycles between and including 1 deposition cycle and about 1,000 deposition cycles. The term “pulsed CVD,” as used herein, may denote a CVD process, that through short exposure/pulse times to the precursors, does not display self-limiting growth, as may be characteristic of ALD processes. Exposure/pulse times for a pulsed CVD may be, for example, about 70-170 ms for an organometallic precursor, such as a metal nitride precursor, and about 60-120 ms for a co-reactant, such as a nitrogen-containing co-reactant. In some embodiments, the metal nitride films/layers provided by methods of the inventive concept may be aluminum nitride (AlN) films/layers. In some embodiments, the metal nitride films/layers may be gallium nitride (GaN) films/layers. In some embodiments, the metal nitride films/layers may be indium gallium nitride (InGaN) films/layers. In some embodiments, the metal nitride precursors for preparing AlN films/layers include, e.g., trimethyl aluminum (TMA), tris(dimethylamido) aluminum (TDMAA), and/or tris(diethylamido) aluminum. In some embodiments, the metal nitride precursors for preparing GaN films/layers include, e.g., trimethyl gallium (TMG), tris(dimethylamido) gallium (TDMAG), and/or tris(diethylamido) gallium (TDEAG). In some embodiments, the metal nitride precursors for preparing InGaN films/layers may include trimethyl indium (TMI). In some embodiments, the nitrogen-containing co-reactant for preparing metal nitride films/layers may include hydrazine (N2H4). In some embodiments, the nitrogen-containing co-reactant for preparing metal nitride films/layers may include ammonia (NH3)
In addition to, for example, exposing a substrate to at least one cycle of a pulse of an organometallic chemical precursor and a pulse of a co-reactant of an ALD process, optionally including a purge between the pulse, or pulses, of precursor and co-reactant, methods of the inventive concept may include a plasma treatment, such as an inert/noble gas plasma treatment with, for example, argon (Ar), neon (Ne), krypton (Kr), or helium (He) plasma, under a bias voltage, for example, about −5 V, −10 V, about −15 V, about −20 V, about −25 V, about −30 V, about −40 V, about −50 V, or about −75 V bias voltage. In some embodiments, the bias voltage in the plasma treatment is between about −5 V and about −75 V. In some embodiments the bias voltage in the plasma treatment is between about −25 V to about −40 V. The plasma treatment may occur after each ALD cycle, after every other ALD cycle, or regularly after any number of ALD cycles. In some embodiments, the plasma treatment is provided after each ALD cycle of an organometallic chemical precursor pulse and a nitrogen-containing co-reactant pulse. In some embodiments, the plasma treatment is provided after every other ALD cycle of an organometallic chemical precursor pulse and a nitrogen-containing co-reactant pulse. In some embodiments, the plasma treatment is provided after every third ALD cycle of an organometallic chemical precursor pulse and a nitrogen-containing co-reactant pulse.
It will be appreciated that temperatures at which methods of deposition of films/layers, such as deposition of templating films/layers and/or buffer films/layers and the like, of the inventive concept should be such that the methods of deposition may be compatible with back end of line (BEOL) processing and integration. In some embodiments, the temperature at which methods of the present inventive concept take place is less than or equal to about 400° C. In some embodiments, the temperature at which methods of the present inventive concept take place is less than or equal to about 450° C., less than or equal to about 500° C., less than or equal to about 550° C., less than or equal to about 580° C., or less than or equal to about 600° C. In some embodiments, the temperature at which methods of the present inventive concept take place is between about and including 350° C. and about and including 400° C. In some embodiments, the temperature at which methods of the present inventive concept take place is between about and including 350° C. and about and including 580° C., between about and including 400° C. and about and including 580° C., between about and including 450° C. and about and including 580° C., between about and including 500° C. and about and including 580° C., between or about and including 550° C. and about and including 580° C.
The pressures at which methods and steps in the methods of the present inventive concept are not particularly limited, and may be any pressure may be used that would be envisioned by one of skill in the art to perform the methods and steps in the methods as described herein. For example, the organometallic chemical precursor pulse(s) and the nitrogen-containing co-reactant pulse(s) may be performed at pressures between about 10−8 Torr to about 10−2 Torr. In some embodiments, the deposition/pulses may be performed at a base pressure at or less than about 1×10−4 Pa (about 7.5×10−7 torr) The pressures at which the plasma treatment takes place may be between about 10−4 Torr to about 10−2 Torr, for example, but not limited to, about 4×10−3 Torr or about 5×10−3 Torr.
Methods of the inventive concept include preparing and depositing thin films/layers, such as a first, template/buffer layer, upon which a second, further layer/film, such as a thick or thicker layer/film (e.g., thicker than about 70 nm), may be grown/deposited. In some embodiments, the first, template/buffer layer may have a thickness of about 20-50 nm, about 20-40 nm, or about 20-30 nm, and may be prepared, for example, by pulsed CVD at a temperature of about 580° C., or by ALA at a temperature of about 400° C. The second, further layer/film may have a thickness of about 100-500 nm, about 100-400 nm, about 100-300 nm, about 100-200 nm, about 100-190 nm, about 150-190 nm, or about 150-170 nm, and may be deposited by, for example, sputtering, in a process that, in some embodiments, is performed without active substrate heating, i.e., heat is not intentionally or purposefully applied to the substrate. In some embodiments, the process takes place at a temperature of less than, e.g., about 100° C., such as between about 20-80° C. during and following deposition of the second, further layer/film. In some embodiments, the average crystallite grain size of AlN in the thin film/layer may be about 6-25 nm, for example, about 6-8 nm, about 10-15 nm, about 10-25 nm, or about 20-25 nm. In some embodiments, the average crystallite grain size of AlN in the thin film/layer and/or the second, further layer/film may be about 10 nm or greater. In some embodiments, the average crystallite grain of the second, further film/layer may be about 20 nm or greater, about 30 nm or greater, about 40 nm or greater, about 50 nm or greater, about 60 nm or greater, about 70 nm or greater, about 80 nm or greater, about 90 nm or greater, up to about 100 nm in size.
Having described various aspects of the present invention, the same will be explained in further detail in the following examples, which are included herein for illustration purposes only, and which are not intended to be limiting to the invention.
The examples that follow show the use of tris(dimethylamido) aluminum (TDMAA) at 400° C. and 580° C. to deposit AlN by a pulsed chemical vapor deposition (CVD) method on non-lattice matched (Si) substrates and lattice-matched (SiC) substrates with growth rates up to ˜45 nm/h. At 580° C. the films show growth of columnar grains. Films produced by the pulsed CVD method at 580° C. template preferentially in the c-axis orientation in additional AlN deposited by reactive sputtering. Films prepared at 400° C. and 580° C. show a similar result in enhancing AlN(002) orientation. On 4H—SiC, epitaxy is observed in the 580° C. pulsed CVD method, which greatly enhances the crystallinity of low temperature (<100° C.) sputtered material when used as a templating layer.
Silicon wafers with (100) and (111) orientations were obtained from WaferWorld. Silicon carbide wafers of 4H polymorph with a 4° off-c-axis cut were obtained from El Cat, Inc. Substrate coupons were degreased using acetone, methanol, and water (Fisher Scientific) and stripped of native oxide by a three-step cyclic etch in 2% HF in deionized water (VWR). Tris(dimethylamido) aluminum (III) was supplied by EMD Performance Materials; anhydrous hydrazine was supplied by RASIRC.
The pulsed CVD was performed in a homebuilt vacuum chamber (walls heated to 90° C., base pressure <1×10−4 Pa) pumped by an Edwards EPX 500 NE high vacuum pump with an in-line liquid nitrogen trap. A tool schematic is shown in
The pulsed CVD process was performed at substrate temperatures of 400° C. and 580° C. The TDMAA precursor container was heated to 105° C. for deposition and held at 85° C. for storage. All precursor dosing was controlled by a LabView system and was performed in a manner consistent with ALD: the precursors were pulsed in an alternating fashion separated by brief periods of pumping. The process is denoted as pulsed CVD because the TDMAA precursor did not display self-limiting growth, as is characteristic of ALD processes, for the short pulse times utilized in this study. Similar behavior has been observed for the deposition of AlN using TDMAA and NH3. Both precursor containers were pressurized with Ar prior to dosing; trace water and oxygen were removed from the Ar push gas using an Entegris GateKeeper purifier. The pulse times used for 400° C. and 580° C. deposition are shown in Table 1 and were optimized to achieve 1.2-1.5 Å/cycle growth rates.
Table 2 describes the samples deposited for the three studies performed. An initial set of thin films with 40 nm target thickness were deposited by pulsed CVD on Si(111) and Si(100) at 400° C. and 580° C. to evaluate the effects of lattice mismatch and substrate temperature. A second set of depositions was performed on Si(111) to analyze the templating ability of the 580° C. pulsed CVD relative to a previously reported ALA technique using Ar ions bombardment at −25 V DC substrate bias: a 20-30 nm template layer by either method was first deposited followed by 150-170 nm of sputtered AlN. These two templated films are compared to a reference 190 nm AlN sputtered film deposited directly onto Si(111). A third set of depositions compares the effectiveness the 580C pulsed CVD template layers on 4H—SiC to a reference sputtered film; 20 nm and 40 nm template layers were deposited and all samples were brought to a total thickness of 190 nm by reactive sputtering. For all templated samples layer thicknesses are approximate and were based on observed growth rates. Reactive sputtering was performed using a 69% N2/31% Ar gas mixture (Praxair and AirGas, >99.999%) in a balanced magnetron configuration (Kurt J. Lesker Torus MagKeeper, >99.99% purity Al target) with 100 W DC power operating at 0.43 Pa as measured by a capacitance manometer (Kurt J. Lesker Co.). Samples were not actively heated during sputter deposition, however a thermocouple mounted on the sputtering stage showed increases from 20° C. to 70-80° C. following deposition.
The surface composition of the films was determined by x-ray photoelectron spectroscopy (STAIR Instruments DESA 150 CMA, Mg Kα source) of the Al2p, N1s, C1s, O1s and Si2p regions. Peak fitting (CASA XPS) was performed using a Shirley background profile and elemental composition was corrected using Scofield relative sensitivity factors. All photoelectron spectra were referenced to adventitious carbon at 284.8 eV.
For all film depositions on Si(111) and Si(100), grazing incidence x-ray diffraction (GI-XRD) was performed to analyze film crystallinity and preferred orientation (Rigaku SmartLab, Cu anode operating at 2 kW, parallel beam configuration, fixed 1.005° incidence angle). X-ray reflectivity measurements of the thin film samples from 0 to 3° 2θ were performed on the same instrument and were modeled using Rigaku GlobalFit software to determine film thickness and density. Bragg-Brentano x-ray diffraction was used for films deposited on SiC due to its comparatively lower instrumental broadening; this allowed for resolution of AlN and SiC diffraction peaks that are not easily resolved in GI-XRD.
Four types of transmission electron microscopy (TEM) were performed: bright filed (BF-TEM), dark field (DF-TEM), scanning (STEM), and high-resolution (HR-TEM). Selected area electron diffraction (SAED) was also performed for films on SiC. All lamellae were prepared using a focused ion beam (FIB) milling system with thinning to approximately 40 nm by Covalent Metrology (Sunnyvale, CA). All TEM, STEM, and SAED was performed using a ThermoFisher Talos F200X G2 transmission electron microscope.
Representative composition data as determined by XPS is shown in
Photoelectron spectra and corresponding peak fits used for the determination of film composition of these samples are shown in
Note the N1s spectra are fit using two peaks, as is customary in XPS characterization of aluminum nitride films; the main nitride peak is located at 397.0 eV and the higher binding energy peak at 398.8 eV corresponds to O—Al—N bonds likely present on the oxidized film surface. It is commonly reported that the charge-balanced sum of nitrogen and oxygen content should equal that of aluminum. While the stoichiometry of the bulk AlN was not measured (e.g., by depth profiling XPS), it is likely that the concentration of oxygen and nitrogen in the bulk of the films may equal that of aluminum and the films are, therefore, stoichiometric.
Results from the grazing-incidence x-ray diffraction study are shown in
As listed in Table 3, the films deposited at 580° C. have greater density than their 400° C. counterparts, with increases of 8.4% and 17.6% observed for the films on Si(111) and Si (100), respectively. It is noted that the largest film density observed, 3.11 g/cm3 for the film deposited at 580° C. on Si(111), is still less than that of bulk AlN at 3.26 g/cm3. This is likely due to the presence of amorphous material at grain boundaries and at the Si—AlN interface.
The data in
These GI-XRD results are complimented by the electron microscopy and diffraction studies of the thin films deposited at 400° C. and 580° C., shown in
For AlN to be utilized as a buffer layer for the growth of GaN and InGaN on silicon and silicon carbide, goals of the RF and microLED industries, thicker layers with c-axis orientation are necessary. In
ALA was performed using a 20 s ion bombardment at the end of each precursor dosing cycle, with Ar ions generated by an inductively coupled plasma source. For this ion bombardment process, the substrate was biased to −25 V DC to accelerate the ions toward the growth surface to crystallize the material. Experimental details can be found previously. These two templated films are also compared to a reference film of 190 nm sputtered AlN on Si(111) by GI-XRD (black line in GI-XRD comparison). AlN deposited by this sputtering condition showed 49.4 at. % Al, 42.5 at. % N, 5.1 at. % O, and 3.1 at. % C composition by XPS.
The GI-XRD comparison inset (
The crystallinity of sputtered material on 4H-SiC is also enhanced when grown on template layers deposited by the 580° C. pulsed CVD process. Shown in
The efficacy of the pulsed CVD templating layers on SiC are made clear by the TEM, SAED, and HR-TEM shown in
Further analysis of the epitaxial relationship of the CVD-templated sputtered film shown in
The epitaxial growth of the 580° C. CVD template layer may be the result of comparatively greater adatom mobility on the growth surface due to the considerably higher substrate temperature and slower growth rate. In comparison, the initial amorphous region of the directly sputtered film may be the result of the combined higher deposition rate and a comparatively colder initial growth surface as the SiC substrate was not actively heated during sputtering. These effects likely resulted in constrained surface adatom mobility. For films deposited on SiC, these XRD, TEM, and SAED results demonstrate that the enhancement mechanism of the sputtered material is not a function of the CVD template layer thickness, but rather is the result of sputtering AlN onto a highly crystalline and lattice-matched CVD template layer.
These results demonstrate that a 580° C. pulsed CVD process for aluminum nitride is a viable alternative to more complex techniques such as atomic layer annealing and techniques requiring substantially greater substrate temperatures, such as MBE and MOCVD. Using tris (dimethylamido) aluminum and anhydrous hydrazine, crystalline films with low oxygen and carbon content can be achieved at temperatures as low as 400° C., though substantial improvement in crystallinity and density is observed at 580° C. When performed on SiC substrates, the 580° C. process demonstrates an epitaxial relationship with the substrate and forms a single crystal; this greatly enhances the crystallinity of reactively sputtered AlN with no active substrate heating. This technique may be used for the growth of crystalline AlN buffer/templating layers for GaN and InGaN on silicon and silicon carbide, enabling a decrease in substrate costs for RF power electronics and for thermally conductive buffer layers for microLED devices.
The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Further embodiments of the present inventive concept are exemplified in the following claims.
The present application claims the benefit of U.S. Provisional Application Ser. No. 63/364,005, filed May 2, 2022, the entirety of which is incorporated herein by reference.
This invention was made with government support under Grant No. HR0011-18-3-0004 awarded by the Department of Defense Advanced Research Projects Agency (DARPA). The government has certain rights in the invention.
| Number | Date | Country | |
|---|---|---|---|
| 63364005 | May 2022 | US |
