Patent Application
20250230578
This application includes material which is subject or may be subject to copyright and/or trademark protection. The copyright and trademark owner(s) has no objection to the facsimile reproduction by any of the patent disclosure, as it appears in the Patent and Trademark Office files or records, but otherwise reserves all copyright and trademark rights whatsoever.
Diamond crystalline materials, with their wide bandgap of 5.47 eV and a host of extreme physical properties, stand out as a premier choice for advanced electronic and quantum applications. Renowned for the highest thermal conductivity (>2000 Wm{circumflex over ( )}−1K{circumflex over ( )}−1), exceptional electron and hole mobilities (>3000 cmV{circumflex over ( )}−1 s{circumflex over ( )}−1), and formidable breakdown field strength (10 MV cm{circumflex over ( )}−1), diamond's intrinsic attributes surpass those of conventional silicon and other wide-bandgap semiconductors. These properties position diamond as an ideal material for high-frequency field-effect transistors (FETs), power electronics, single-photon emitters, high-precision sensors, and cutting-edge quantum computing components. Despite its theoretical superiority and wide-ranging potential applications in harsh working conditions, the full exploitation of diamond's capabilities in devices like power diodes, photoconductive switches, and advanced detectors is hindered by substantial challenges. Fundamental obstacles include the difficulty in achieving shallow, thermally-activated n-type doping, controlling the quality and character of its crystalline structure, and a limited understanding of defect-related transport properties. Although doping with elements like boron, nitrogen, and phosphorus, as well as more exploratory halogens and lithium, has shown promise, a comprehensive understanding of the interplay between diamond's geometric and electronic properties—especially how these influence the band gap and defect states—is critically needed. As such, the development of diamond-based electronics and quantum devices requires not just incremental improvements in material processing and doping strategies but a revolutionary approach to harnessing and tailoring its unique properties for next-generation technologies.
The disclosed embodiments include the co-doping of lithium (Li), boron (B), and phosphorus (P) in nanocrystalline diamond (NCD) thin films, focusing on the enhancement of electrical properties and the underlying structural changes. Ion implantation was used for doping, followed by rapid thermal annealing (RTA) to achieve optimal dopant distribution. The films were characterized using Raman spectroscopy, secondary ion mass spectrometry (SIMS), and scanning transmission electron microscopy (STEM) to analyze doping profiles, crystal structure, and surface morphology. Electrical properties were evaluated through Van der Pauw measurements, revealing a high carrier concentration of 5.047×10{circumflex over ( )}18 cm{circumflex over ( )}−3, low resistivity of 1.228×10{circumflex over ( )}2 Ohm/sq, and high mobility of 347.47 cm{circumflex over ( )}2/Vs. These results indicate that co-doping significantly improves the electrical performance of diamond, making it a viable approach for diamond-based electronic devices. The disclosed embodiments highlight the impact of crystallographic orientation and dopant clustering on the observed properties.
In some disclosed embodiments, the disclosure herein presents a new and improved system and method for fabricating enhanced diamond semiconductor materials and devices. In accordance with one aspect of the approach, a specific percentage of the substituent donor atoms contribute to the lattice's conduction electrons instead of contributing to the competing intermediate band states, providing higher carrier mobility to be realized than the state of the art, wherein donors show ionization energies in the range of 0.15 to 0.3 eV, and where mobilities over 800 cm2/Vs can be realized at room temperature. The disclosure suggests broader applications and advantages of this approach in semiconductor technology.
In some disclosed embodiments, the disclosure herein, In another aspect of a disclosed approach, a method of fabricating substituent doped diamond semiconductor materials may include the steps of selecting a diamond Lattice material with RRQF of at least 133.2, introducing a minimal amount in the range of 1×108/cm−2 to 1×1011 cm−2, of interstitial dopant atoms to the diamond lattice to create interference with vacancy wavefronts, introducing a minimal amount in the range of 1×108 cm−2 to 1×1011 cm−2, of substituent acceptor strain dopant atoms, introducing a plurality of substituent donor dopant atoms in the range of 5×1010 to 5×1015 cm−2, and pulsed laser irradiation using laser wavelengths of 550 nm or lower, wherein the combination of vacancy wavefront impedance and induced biaxial stress allow for substituent dopant geometries to realized and electronically activated by laser irradiance in lieu of thermal annealing techniques.
In another aspect of an approach, novel n-type and novel p-type substituent doping techniques are combined with novel fabrication methods for quantum optical defect creation and photonic components to create a monolithically integrated quantum photonic modulator device, where the quantum pair source, is modulated on chip, and where a fully diamond quantum photonic system is realized for the first time.
The benefits of the disclosed techniques and approach are broad and functional, promising significant advancements in the fields of high-frequency field-effect transistors, power electronics, single-photon emitters, high-precision sensors, and quantum computing components. The invention claims support this by detailing specific steps and conditions for manipulating diamond material properties, emphasizing an innovative combination of doping strategies, lattice manipulation, and annealing techniques.
The foregoing disclosure, including the drawings and detailed description, reveals various systems, methods, aspects, features, embodiments, and advantages related to the fabrication of diamond semiconductors. Those skilled in the art will recognize additional elements within this domain upon review of the provided materials. This disclosure intends to encompass all such supplementary systems, methods, aspects, features, embodiments, and advantages as part of this description and to include them within the ambit of the claims that follow.
The drawings provided are intended solely for illustrative purposes. It should be noted that the components depicted in these figures may not be to scale. The primary focus is on demonstrating the fundamental principles of the system described herein. In these illustrations, identical reference numerals are used to identify the same elements across various views.
These and other aspects of the present invention will become apparent upon reading the following detailed description in conjunction with the associated drawings.
The following detailed description is directed to certain specific embodiments of the invention. However, the invention can be embodied in a multitude of different ways as defined and covered by the claims and their equivalents. In this description, reference is made to the drawings wherein like parts are designated with like numerals throughout.
Unless otherwise noted in this specification or in the claims, all of the terms used in the specification and the claims will have the meanings normally ascribed to these terms by workers in the art.
Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise,” “comprising” and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in a sense of “including, but not limited to.” Words using the singular or plural number also include the plural or singular number, respectively. Additionally, the words “herein,” “above,” “below,” and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application.
The following description combines and references the drawings to illustrate and teach one or more specific embodiments of the present application. These embodiments, offered not to limit but only to exemplify, are presented in sufficient detail for those skilled in the art to practice as claimed. The description aims to make the objects, technical solutions, and advantages of these embodiments clear and comprehensible. It may omit certain information known to those of skill in the art for brevity and assumes the examples were conducted under conventional conditions or those recommended by the manufacturer, using commercially available conventional products. The focus is on clarity and completeness, providing a technical understanding while acknowledging the expertise of the intended audience, and that those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.
The development of electronic and optical defects in diamond semiconductor in the prior art has limitations, where the main activities include: the theoretical ionization energies of potential donor dopants such as nitrogen, phosphorous, lithium and sodium, with theorized activation energies of 1.7 eV, 0.2-0.6 eV, 0.1 eV, and 0.3 eV, respectfully, acceptor dopants such as Boron, with theorized activation energy 0.1-0.37 eV, and optical vacancy-dopant defects such as nitrogen-vacancy (N-V), silicon-vacancy (Si-V) and germanium-vacancy (Ge-V), with a range of electron-spin coherence times based on various factors such as concentrations and interrelated band splitting effects. In practice, only deep donor activation energies with low carrier densities at ambient conditions are demonstrated, with attempts at incorporating higher donor or acceptor dopant concentrations leading to graphitic-like band bending, decreased carrier mobilities with charge carrier transport via hopping conduction, and further compromised electronic properties, especially noticeable with temperature variations. These dopants are invariably introduced alongside compensating/passivating defects such as interstitial-vacancy defects, vacancy chains and dislocation fronts, which further degrade the electronic performance and erode the inherent advantages of diamond materials. Moreover, the ambition to enhance the density of optical defect centers in diamond quantum systems invariably clashes with the need to maintain long carrier lifetimes or long electron-spin coherence times, resulting in detrimental trade-offs. Despite the theoretical promise of diamond crystalline materials for advanced electronic and quantum devices, practical demonstrations have consistently grappled with significant technological barriers due to fundamental gaps in diamond defect knowledge.
Another major failing of the prior art can be seen in the dubious nature of diamond crystalline geometry and defect incorporation therein, where potential dopant donors such as Li and N show electronic band gap states in polycrystalline diamond systems not replicated in the single crystal diamond system of any orientation, such as nitrogen incorporation in ultrananocrystalline diamond, so-called N-UNCD. Additional manifestations of this problem include phosphorous doping concentration versus ionization efficiency in (111) oriented versus (100) oriented single crystal diamond. This constitutes a major failing of prior art as claims must particularly point out and distinctly define the metes and bounds of the subject matter that will be protected, and materials ranging from single-crystal diamond to various forms of polycrystalline diamond and mixed-amorphous diamond-like materials, such as diamond-like-carbon, so-called DLC, and so-called Q-Carbon, each with their unique sp2 and sp3 bonding states, present diverse mechanical, optical, and electronic characteristics. These enduring challenges not only reflect a gap in achieving the full potential of diamond materials but also underscore the serious implications for the advancement of semiconductor and quantum technologies. The persistent defects, particularly in nanocrystalline films, compromise not only the electronic and optical properties but also the mechanical integrity, significantly limiting the application of diamond in demanding environments. The collective struggle to achieve full activation of dopants, maintain high carrier mobilities and coherence, ensure long-term stability, and preserve the mechanical robustness of diamond films represents a critical bottleneck in unlocking the full suite of diamond's exceptional attributes.
Accordingly, there is an unmet need presently in addressing these multifaceted challenges in enabling shallow substituent dopant materials and thereby enabling novel power electronic devices, amongst other applications.
The substituent doped diamond, the preparation method thereof, the semiconductor and/or semimetal material and devices in the embodiments of the present are specifically described below.
The inventor discovers that in the process of implementing the application: diamond, whether in single crystal, microcrystalline, or nanocrystalline form, shares the same fundamental building block of the carbon atom arranged in a tetrahedral lattice. The variations come in the form of grain boundaries, defects, and overall crystallinity. From a topological standpoint, it is considered that each form of diamond is a different “state” or manifestation of the same underlying material. Topologically, it is considered that the invariance in the molecular structure of carbon atoms in the diamond lattice across these different forms. While the macroscopic properties such as electrical conductivity, hardness, etc., change significantly between single-crystal and nanocrystalline diamond, the local bonding environment of each carbon atom remains tetrahedrally coordinated with four other carbons in a sp3 bond state arranged in variable geometric diamond structure. This is considered herein as a type of “local” topological invariance. In the case where sp3 bonding is maintained amongst two coordinated carbon atom molecular states, the so-called dimmer pairs seen in higher volumes in nanocrystalline (NCD) and ultrananocrystalline (UNCD) diamond volumes, the topological state is seen distinctly changed, where under UV Raman Spectroscopy the diamond signature peak is shifted in favor of the 1335 cm−1 to 1390 cm−1 region, and the intensity of contributions from the graphitic band are seen to correspondingly increase. This shows while the Raman spectroscopy technique can be quite sensitive to carbon bond states in the various diamond allotropes, techniques such as X-ray diffraction or XRD analysis, are less sensitive, as even UNCD materials can show primarily (111) predominance, masking the local geometric states amongst global orientations. The points in the proposed topological space then represent different states or conditions of the diamond material, characterized by their specific Raman signatures. Each point corresponds to a particular set of physical properties or structural characteristics of the diamond, such as grain size, crystallinity, and defect density. The neighborhoods of each point could be defined by variations in the Relative Raman Quality Factor, RRQF. For example, a neighborhood could consist of all diamond states that have Raman signatures within a certain range of RRQF. This captures the notion of “closeness” or similarity between different diamond states in terms of their Raman characteristics and related molecular properties. RRQF, as defined by the intensity and sharpness of the diamond Raman peak at 1332 cm−1 (indicative of sp3 bonding) and its relation to any graphitic G-band features (indicative of sp2 bonding), provides a measure of crystal quality and ordering. This factor can then serve as a boundary defining the extent of the neighborhoods. Whereas, in quantum optics the quality factor is known to be defined as the frequency divided by the Full Width Half Maximum about the frequency or QF=f/FWHM; Herein, we define RRQF specifically for a Raman Shift using UV Raman Spectroscopy: RRQF=(λD/FWHMD)·(ID/IG) where λD is the diamond signature peak (1332 cm−1), FWHMD is the Full width at half maximum of the diamond peak about the region 1330 to 1390 cm−1 of the band, as used herein the terms ID and IG are defined as the Intensity of the diamond peak at 1332 cm−1 and the Intensity about the graphitic band (G-band), respectively and both are measured normatively in counts or arbitrary units depending on the Raman spectroscopy system's calibration. Further wavelength is used in lieu of frequency for the convenience of producing terms that do not require exponents to denote. The ratio ID/IG is a dimensionless quantity as it's comparing the relative intensities of two spectral features. For example, a diamond peak 1332 cm−1 with FWHMD of not more than 20 cm−1 and a ID/IG ratio of at least 2 yields the RRQF value of 133.2. Therefore, given that the RRQF is a ratio of these quantities, the ultimate units of RRQF itself are dimensionless, as it represents the product of a pure quality factor and a probability amplitude of diamond's structural integrity based on its Raman signature. The dimensionless nature makes it a versatile and comparative metric that can be used across a plurality of different samples and conditions. Therefore, a success of the disclosed approach, the presented disclosures can be promptly applied to the development of practical diamond based optical and electronic materials with any chemical composition and atom arrangement (i.e. single crystal, microcrystalline, nanocrystalline and ultra nanocrystalline diamond).
The inventor discovers further that in the process of implementing the application: The ideal perfect single crystal diamond lattice, the naturally occurring so-called type IIa diamond contains within it a volume of vacancies that introduce localized states within the diamond electronic band gap, as physically evidenced via cathodoluminescence (CL) by the characteristic so-called Band-A luminescence at approximately 2.9 eV, or in the range of 2.13 eV to 3.13 eV above the conduction band, known to those skilled in the art to correspond to the neutral donor vacancy of the self-interstitial. Further, the Band-A luminescence is seen quenched either through annealing above temperatures of 420 degrees Celsius and/or through vacancy-interstitial defect formation in the presence of nearby interstitial dopants, and through dislocation front formations such as diamond grain boundaries. At sufficient density, the vacancy states begin to overlap to form “bands” of states situated at about 2.9 eV or in the range of 2.1 eV to 3.13eVabove the valence band, however, these are not the bands of the native diamond system, i.e. the conduction or valence bands, but rather instead, a dense collection of localized states within the band gap constituting a competing intermediate band. These states can trap charge carriers, altering the electronic and optical properties of the diamond. Furthermore, as vacancy defects exist with different charge states, these states mediate processes like non-radiative recombination as well as introduce new optically active transitions (e.g. N—V, Si—V, Ge—V centers in diamond). For example, some defects might act as donors, while others act as acceptors. The net effect on the electronic properties would depend on the relative concentrations and energy levels of these defects. Where the presence of vacancy related defects introduces trap states within the intrinsic diamond band gap, these trap states can be represented as: Et=Ev+Etrap, where Et is defined as the energy of the trap state, Ev is the energy of the valence band maximum, and Etrap is the energy of the defect state relative to the valence band maximum. For a semiconductor with defects, the density of states g(E) near the Fermi level (EF) due to vacancies can be approximated as g(E)=g0(E)−Δg(E), where: g0(E) is defined as the density of states without defects and Δg(E)=Nvδ(E−Etrap), where Nv is defined as the density of vacancies, and δ(E−Etrap) is defined as the Dirac delta function representing the energy level introduced by the defect. The E−Etrap term is known where 5.47 eV-2.9 eV, and the Direct delta function is bounded by solutions between 0 and 1. Thus, at room temperature, either all intrinsic electron carriers within the host diamond lattice occupy the plurality of Etrap states as the lowest possible electron state corresponding to the conduction band, or by zero solution to the Dirac delta function, all trap states are quenched and the density of states is equivalent to those of the defect free system. Untreated, the intermediate band (IB) will fix the fermi level and the corresponding fermi surface to IB associated states, instead of lying halfway between the conduction and valence bands of the host diamond system at ambient pressures and temperatures. Further, even for donor-type defects sufficiently close to substitutional positions within the diamond lattice, but interstitially located, achieving full activation (i.e., every dopant atom contributing a free carrier) will remain a challenge, especially for n-type dopants. Untreated, the effective doping will be lower than the introduced dopant concentration. It is also known that at annealing temperatures above 420 C, neutral vacancy levels are quenched, whereby neutral interstitials have combined to form divacancies, amongst other complexes. As such, the temperatures normative to diamond growth via CVD and HPHT methods, and in-situ doping methods practiced therein, most probabilistically would yield the dopant states associated with the IB, and as such demonstrate low carrier mobilities, poor activation, etc. as seen by practical demonstrations of diamond semiconductor materials and devices heretofore. Therefore, another failing of the prior art, dopant experiments to date have shown varying degrees of vacancy-interstitial defect electronic contribution and not n-type doping of the diamond system. Furthermore, the term substituent dopant is used in place of substitutional dopant intentionally heretofore to distinguish between carrier states added through the replacement of a carbon atom and carrier states added through vacancy-defect complex created states associated with the intermediate band in the topological space.
The second step 104 of method 100 may include introducing a minimal amount of interstitial dopant atoms to the diamond lattice to create interference with vacancy wavefront. The introduction of interstitial dopant atoms may disrupt or alter the usual propagation of these waves and may cause a diminution of the extended effects caused by vacancies and their propagation. The interstitial dopant may be but is not limited to lithium, sodium, and hydrogen. The minimal amount of interstitial atoms of second step 104 may be for example, but is not limited to, approximately 1×108 cm−2 of lithium. In other embodiments, the minimal amount of interstitial dopant atoms of second step 104 may be for example, but is not limited to, approximately 1×109 cm−2 of lithium, and a range of 1×108 cm−2 to 1×1010 cm−2 where the thickness of the co-doped diamond is generally 0.5 um to 5.0 um. Second step 104 may be accomplished by interstitial co-doping at extremely low to room temperatures in that interstitial defects and vacancies may be limitedly mobile, but lithium may take interstitial positioning. The second step 104 may create mobile vacancies for subsequent dopants, in addition to some substitutional positioning through the vacancies created by self-interstitials displaced by the impinging ion.
The third step 106 of method 100 may include introducing a minimal amount in the range of 1×108 cm−2 to 1×1011 cm−2, of substituent acceptor strain dopant atoms. The substituent dopant atoms may be introduced to the diamond lattice through the ion tracks created by step 104. For example, third step 106 may include introducing smaller substituent dopant atoms using ion implantation at energies less than 1 MeV to minimize localized self-annealing effects and maintain precise layer control within the topological space. The smaller co-dopant may introduce biaxial strain, which may be more easily accommodated in the through reorientation of the local geometries, such as for example the <100> orientation. The acceptor substituent dopant may be, but is not limited to, Boron or Aluminum. The minimal amount of interstitial atoms of third step 106 may be for example, but is not limited to, approximately 1×108 cm−2 of boron. In other embodiments, the minimal amount of interstitial dopant atoms of third step 106 may be for example, but is not limited to, approximately 1×109 cm−2 of boron, and a range of 1×108 cm−2 to 5×1010 cm−2 where the thickness of the co-doped diamond is generally 0.5 um to 5.0 um. Third step 106 may be accomplished by interstitial co-doping at extremely low to room temperatures in that interstitial defects and vacancies may be limitedly mobile, but boron may take both substituent and interstitial positioning. The third step 106 may create mobile vacancies for subsequent dopants, in addition to some substitutional positioning through the vacancies created by self-interstitials displaced by the impinging ion.
In the fourth step, 108, a plurality of substituent donor dopant atoms is introduced. The as-implanted diamond topological space with local vacancy wavefront interference and/or diffraction, and the biaxial system stress induced in the lattice from second step 104 and third step 106, facilitates the introduction of donor dopants into near substituent positioning. The substituent donor dopant may be for example but is not limited to Phosphorous, Nitrogen, Sulfur, and Oxygen. Donor atoms will have at least one more or more valence electrons than carbon, which perturb the electronic structure. Where the plurality of substituent donor dopant atoms exceeds the minimized concentration of remaining unquenched vacancy states about the topological space, and where the sp3 bonding in diamond allows for angular momentum conservation through bond reorientation, the introduction of further donor dopants must be accompanied by a localized reorientation, in accordance with the least time principles of crystalline growth mentioned in the preceding section. For example, for (111) or (110) surface, reorientation about the (100) plane might offer more favorable bonding configurations that minimize energy and preserve angular momentum when accommodating both P and the smaller co-dopant, where the (111) inter planer distances are known to be 0.206 nm and where the (100) inter planer distances are known to be about 0.356 nm, the (100) plane would be the most remote point perpendicular to both (111) and (110) surfaces. The effective reduction or elimination of voids is also attributed, in part, to the more consistent growth direction. A consistent growth direction can lead to a more compact and regular arrangement of atoms, reducing the likelihood of voids or defects. Furthermore, as the surface reconstruction changes the <111> or <110> surface to <100>, the volume becomes further compacted.
In one embodiment, the ion implantation of step 108 may be performed using Phosphorus at or below approximately 0 degrees Celsius to impede vacancy and interstitial diffusion out of target layers, preserving depth controls afforded by the technique.
An embodiment of the application uses ion implantation of step 108 with tilt angles greater than 6 degrees in the implantation step 108, where underestimation of implantation depth in known to occur due to channeling of dopants in ion implantation of crystalline materials. Channeling is a known issue to those skilled in the art, and where the critical angle for a given ion dopant is known to be a function of ion implant mass and lattice constant parameters, and where said parameter is known for single crystal diamond to be approximately 0.3567 nm for the (100) oriented diamond and approximately 0.206 nm for the (111) oriented diamond diffraction planes. Doping may be performed on a Varian Ion Implantation System with a phosphorus mass 31 singly ionized dopant (i.e., 31P+).
An embodiment of the application provides a substituent doped diamond, the lattice structure of doped diamond comprises a plurality of carbon atoms, a lithium atom, a boron atom, and a plurality of phosphorus atoms, and a plurality of vacancies, with concentration of donor atoms at least 0.000568% of the diamond volume per cubic centimeter, which in the present embodiment is principally phosphorous, provide conduction electrons having ionization energies less than 0.31 eV.
An embodiment of the application provides ion implantation where the target species are doped molecularly instead of as individual ions, such as for example but not limited to, dopant adenine, C5N4Hn, the molecular ion will dissociate immediately at the surface into atomic components, entering the volume with equal velocities. The stopping depth would therefore be determined by implant mass energies, and as such, depth control may still be accomplished with fewer total doping steps. The molecule larger size however will generate more vacancies per ion than single ion doping sequentially and may generate an increase in wanted defects incorporated.
The inventor discovers further still that in the process of implementing the application: substituent dopant atoms may be placed close to neutral vacancies with topological break to local crystal symmetry about the reoriented volume, but can only be stabilized once formed, and will otherwise diffuse out of the doped region to equalize charge balances and arrange in lowest rest energy configurations in the volume. Given sufficient energy or time, the doping profiles immediately following the implantation steps will substantially change. Due to the large energy difference between the top of the lowest conduction band state (approximately 2.9 eV above the valence band) and the conduction band minimum, the prior art fails to provide sufficient pathway to electronic activation of the substituent dopants, where using the annealing approaches implemented to date, that is in-situ CVD and HPHT, oven annealing and rapid thermal annealing, thermal energy is provided to a plurality of vacancy related defects, and the high temperatures utilized favor vacancy-defect complex formation over substitutional donor complex formation, even at short duration. Therefore, optical annealing methods such as pulsed laser irradiation may be utilized to provide sufficient energies to drive dopant electronic activation and recrystallization of the damaged implant layers, however sufficient optical energy should be provided such that vacancy defect mechanisms are suppressed in favor of dopant-vacancy annihilation. With sufficient plurality of electrons transferred from IB states to conduction band and from conduction band minimums to created substituent dopant states, substituent dopant centers will remain relatively undisturbed, where orbitals and the spin states' coherence is protected by the symmetries and topological characteristics of the diamond lattice, making them less susceptible to decoherence mechanisms.
The fifth step 110 of method 100, may include subjecting the diamond lattice to pulsed laser irradiation. The pulsed laser irradiation may be done using laser wavelength of 532 nm, which may be generated by a Q-switched, frequency doubled Nd-YAG laser, and beam energy density of less than 50 Joules/cm2. Pulsed laser irradiation may drive volume compaction through annihilation of vacancy and defect and increased crystalline ordering, and as such may restore integrity to portions of the diamond lattice that may have been damaged during the second step 104, the third step 106, and the fourth step 108 and may electrically activate the dopant substituent atoms. Successive increase to beam energy density with successive pulses may be beneficial as the pulsed laser irradiation drives improved crystal quality through recombination and improved ordering and as such there is ever improving thermal energy dissipation in the system. Further, pulse times in excess of the excitation-relaxation lifetimes, known to be approximately 1.1 ns at room temperature, may be beneficial to drive vacancy-donor conversion efficiencies. The pulsed laser irradiation step 110 may be done in open air and at ambient temperatures and pressures.
Another embodiment of the application uses wavelengths of 193 nm, such as generated by ArF excimer laser, energy densities less than 50 Joules/cm2, and pulse times less than 100 ns, such that energy provided to the system implanted by method 100 is greater than the band gap energy 5.47 eV, and where compaction can be accelerated to form ultra-high crystallinity without deleterious effects to substituent doping.
Another embodiment of the application uses wavelengths greater than 550 nm, such that energy can be provided to form stable quantum optical defect centers in a surrounding high-crystalline quality system, providing long coherence times in excess of 220 us.
For some applications it may be advantageous to degenerately and/or differentially dope different parts of the same diamond wafer, for example, to create n-type (n) and heavily doped n-type (n+), and/or p-type (p) and heavily doped p-type (p+) regions. In embodiments, various semiconductor and quantum photonic devices are created including p-n and p-i-n junction phase shifters, and ring-resonator qubit pair sources.
The second step of method 600 may be the same as the second step 502 of method 500, including cleaning the diamond surface volume to remove organic and ionic contaminants. The third step 602 of method 600, which includes depositing an aluminum charging layer, may be accomplished by physical vapor deposition (PVD) sputter technique utilizing a Kurt J Lesker Sputter system, where Aluminum sputter target is deposited using 200 watts DC power at 5 mTorr pressure under 50 sccm of flowing Argon for 113 seconds, yielding approximately 15 nm of Al thickness. The fourth step 604 of method 600 includes a positive resist spin, bake, E-Beam exposure, and development. The resist may be, but is not limited to, commercially available 495 PMMA A resist. The resist may be applied after a pre-bake for one minute at 180 degrees Celsius, coating 200 nm thickness using a spin speed of 2500 rpm, and a post-spin bake at temperatures between 100 and 180 degrees Celsius for 70 seconds. E-beam exposure may be done using standard e-beam lithography systems such as made by RAITH, using a mask file comprising cross-hatch alignment structures or the like, and may implement 500 um by 500 um write fields at 0.02 um resolution, and beam energy of 2 kV with beam area dose of 375 uC/cm. Post-e-beam exposure, development may be accomplished using known PMMA developer mixture of 1:3 MIBK to Isopropyl alcohol. The fifth step 606 of method 600, which includes RIE etch, descum, and clean, may comprise reactive ion etching which may be practiced using commercial systems such as those manufactured by oxford systems, and where using input parameters such as 300 W forward power, 0V DC bias, 50:1 ratio of 02 to Argon gas sources at 9 mTorr base pressure, etching raters of approximately 40 nm/min may be controllably achieved to the target depth thickness. Descum process, which is known to those of skill in the art, may be achieved using standard dry recipes on commercially available ozone generator systems, such as those manufactured by MKS. The Cleaning step may be the cleaning step 502 of method 500. The sixth step 608 of method 600, which includes clean, dehydration bake, spin HSQ, and bake may include exposing the alignment patterned diamond material of 600 to cleaning with Toluene, Acetone, IPA, and DI water for 2 minutes each, followed by a dehydration bake on a hotplate for 5 minutes at 120 degrees Celsius. HSQ may be spun using a 1 mL pipette to extract 0.75 mL of HSQ and deposited while in spinning, 6% at 1000 RPM for 60 seconds, with 500 RPM ramp up and ramp down before achieving target spin speed, then exposing to hot plate surface at 120 degrees Celsius for 2 minutes, and letting cool down before proceeding. In the seventh step 610 of method 100, which includes waveguide E-Beam write, may include using the e-beam system of the fourth step 604 with a mask file comprising of the structures of integrated quantum photonic modulator device system 700. Where it is known beam area dose of approximately 3000 uC/cm2 is effective for diamond, 2700 uc/cm2 may be utilized to not overexpose in the case of polycrystalline diamond systems with corresponding resolutions of 0.001 μm and beam energy of 10 kV and probe current of approximately 10 nA. In the eight step 612, which includes HSQ Diamond Etch and Clean, post e-beam exposure of the previous step, the material may be developed using commercially available developers containing TMAH such as MF CD-26, which may be heated to 60 degrees Celsius for uniform and timely development. The exposed pattern may be etched similarly to the RIE diamond etch step of 606, adjusting time scales to achieve the target etch dept of 300 nm. Clean steps include removal of remaining HSQ materials and the clean steps of 502 of method 500. Quick removal of HSQ is known to occur with ten second dip in buffered oxide etchant (50:1).
The ninth step 614 of method 600, which includes deposition of patterned implant mask I, which may include the previous steps of fourth step 604 of method 600, utilizing a pattern for n-type region openings in lieu of alignment marks, followed by the deposition of aluminum in the likeness of the third step 602, followed by the next step similar to step 606 of method 600, omitting the etch portion and utilizing descum and appropriate clean, followed by a next step of blanket Aluminum deposition in the likeness of the third step 602, such that portions to be n-type implanted will have differential Al mask thickness of about 30 nm and that elsewhere the thickness of Al will fully block dopants from reaching the diamond surface.
The tenth step 616 of method 600, which includes n-type implantation, may be the same as fourth step 104, fifth step 106, and sixth step 108 of method 500, modifying the dopant dose of phosphorous to 1×1012 cm−2 to achieve target dopant concentration of approximately 1×1020 cm−3 at the desired depth. The eleventh step 618 of method 600 includes strip Al mask I, clean, deposit patterned mask II, which may be the same as the Al etchant seventh step 506 of method 500, and where clean and deposit patterned mask II may repeat the cleaning step 502 of method 500 and the ninth step 614 of method 600, changing the pattern file corresponding to p-type region opens. The twelfth step 620 of method 600 includes p-type implant, which may be the same as fourth step 104, fifth step 106, and sixth step 108 of method 500, modifying the dopant type and dose of fifth step 106 to be minimal substituent donor Nitrogen at 1×109 cm−2, and modifying the dopant type and dose of sixth step 108 to be plurality of substituent acceptor Boron at 1×1012 cm−2 corresponding to target Boron concentration of 1×1020 cm−3 in the diamond volume at the target dept. The thirteenth step 622 of method 600 includes strip mask II, clean, deposit patterned mask III, which may be the same as eleventh step 618 of method 600, changing the pattern file corresponding to openings for the ring-resonator 704 region instead. The fourteenth step 624 of method 600 includes X-V Defect Implant, where X denotes one of the optical defect center generating dopant species such as Nitrogen, Silicon, Germanium amongst potentially others. In the present embodiment, Nitrogen is used, though the same principles and techniques may be practiced with Silicon and Germanium adjusting excitation energy to correspond to those optical centers. The methodology may be the same as the as fourth step 104, fifth step 106, and sixth step 108 of method 500, where the modified goal of creating quantum optical defect centers in lieu of substituent dopants. In the present embodiment steps 104-106 are combine by use of ion implantation of molecular dopant adenine, C5N4Hn, where interstitial defect H, strain dopant C, and optical donor N dope the system, but where strain dopant C can combine with neutral and singly charged vacancies, and where Nitrogen can form complexes but not preferentially occupy substitutional sites after doping. Using ion beam energy of approximately 70 keV, a dose of approximately 1×109 cm−2, and ion beam tilt angle greater than 6 degrees, a uniform doping layer may be achieved sub-surface within the ring-resonator structure 704.
The fifteenth step 626 of method 600 includes strip mask III, clean, deposit laser irradiation mask, and may be the same as eleventh step 618 of method 600, changing the pattern file corresponding to openings for the ring-resonator region 704, n-type doping region 718 and p-type region 726 instead. The sixteenth step 628 of method 600 includes pulsed laser irradiation and may be the same as eight step 110 of method 500. The n-type and p-type regions may be activated using laser wavelength corresponding to the 532 nm transition discussed. Further, as ring-resonator structure 704 calls for quantum defect activation, laser wavelength of 658 nm or 741 nm may be used, where it is known to those skilled in the art such wavelengths correspond to excitation and relaxation between the T2 lowest excited state of conduction band and A2, T1, and E the split off bands and ground states, respectively. Laser power levels may be maintained as previous, adjusting only for change to wavelength and pulse durations. The seventeenth step 630 of method 600 includes strip mask and clean, and may be the same as the seventh step 506 of method 500. The eighteenth step 632 of method 600 includes deposit patterned contact mask, which may include the previous steps of fourth step 604 of method 600, utilizing a mask file pattern for the contact metal opening 728, followed by the deposition of first Titanium (Ti) and next gold (Au). Deposition may be done by PVD method such as on Lesker Sputter systems, where 5 nm of Ti can be deposited using 200 W power, 50 sccm flowing Argon at 4 mTorr chamber pressure for approximately 50 seconds, and where 50 nm of Au can be deposited using 150 W DC Power under 50 sccm of flowing Argon at chamber pressure of 4 mTorr for approximately 180 seconds. The nineteenth step 634 of method 600 includes strip mask and clean steps, and may be the same as the descum and appropriate clean steps of the ninth step 614 of method 600. The twentieth step 636 of method 600 includes metal annealing, which may be accomplished in typical annealing furnaces. The metal furnace annealing may be performed at 350 degrees Celsius for two hours and may include annealing under a forming gas such as H2:Ar, and may be plasma assisted. The twenty-first step 638 of method 600 includes terminating the surface. There are few successful termination schemes for diamond, as known to those of skill in the art, where surface terminations may induce loss of conduction and graphitization at surface sites. The present application produces a stable defect surface, where negative electron affinity may be achieved with appropriate termination scheme. Therefore, the use of hydrogen termination, oxygen termination and hydroxyl termination may be practiced where hydrogen termination may be accomplished under atomic hydrogen producing conditions, oxygen termination may be accomplished by acid exposure followed by ozone treatment, and hydroxy termination may be accomplished by water vapor source exposure during hydrogen termination treatment.
The above descriptions of the disclosed embodiments are provided to enable persons skilled in the art to make, practice or use that which is defined in the application. Other embodiments and modifications will readily occur to those of ordinary skill in the art in view of these teachings without a further inventive step.
The above detailed description of embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise form disclosed above. While specific embodiments of, and examples for, the invention are described above for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. For example, while steps are presented in a given order, alternative embodiments may perform routines having steps in a different order. The teachings of the invention provided herein can be applied to other systems, not only the systems described herein. The various embodiments described herein can be combined to provide further embodiments. These and other changes can be made to the invention in light of the detailed description.
All the above references and U.S. patents and applications are incorporated herein by reference. Aspects of the invention can be modified, if necessary, to employ the systems, functions and concepts of the various patents and applications described above to provide yet further embodiments of the invention.
These and other changes can be made to the invention in light of the above detailed description. In general, the terms used in the following claims, should not be construed to limit the invention to the specific embodiments disclosed in the specification, unless the above detailed description explicitly defines such terms. Accordingly, the actual scope of the invention encompasses the disclosed embodiments and all equivalent ways of practicing or implementing the invention under the claims.
While certain aspects of the invention are presented below in certain claim forms, the inventors contemplate the various aspects of the invention in any number of claim forms.
This utility patent application claims priority from provisional patent application 63/620,477 filed on Jan. 12, 2024 the contents of which are incorporated herein by reference as if restated herein.
| Number | Date | Country | |
|---|---|---|---|
| 63620477 | Jan 2024 | US |
