Large area microwave plasma chemical vapor deposition reactor device and method for providing large area microwave plasma chemical vapor deposition in a reactor chamber

Abstract

A large area microwave plasma chemical vapor deposition reactor apparatus and a method for large area microwave chemical vapor deposition, comprising a reactor chamber and a composite right / left-hand waveguide section, the reactor chamber being adapted to provide a plasma region in the interior of the reactor chamber by electromagnetic energy of a first frequency, the composite right / left-hand waveguide section being adapted to operate at the first frequency at infinite wavelength and having a coupler device in the wall, the coupler device being arranged to couple electromagnetic energy from the interior of the composite right / left-hand waveguide section to the interior of the reactor chamber.

Description

Technical Field

[0001] The present invention relates to a reactor device and a method for microwave plasma chemical vapor deposition (MPCVD). Background Art

[0002] Known microwave plasma chemical vapor deposition (MPCVD) reactors employ a microwave energy source that couples and transmits microwave energy to the interior of an MPCVD reactor chamber. The MPCVD reactor chamber, which forms a resonant cavity for receiving microwave energy, is designed to shape the electric field of electromagnetic energy within the chamber with a field strength near a substrate that is high enough to form a high temperature plasma that promotes a reaction to form a material vapor that will be deposited on the substrate at a nearby location.

[0003] In known MPCVD reactor arrangements for diamond material deposition, microwaves generated by a microwave energy source typically enter the reactor chamber through a conventional waveguide arranged between the microwave radiation energy source and the reactor chamber, thereby coupling the output from the microwave radiation energy source through an opening in the wall of the reactor chamber via a conventional waveguide coupler. The waves that have entered the reactor space are deflected by the walls of the reactor chamber by the design and shape of the chamber, and further propagate by reflection from the inner wall of the chamber, thereby being concentrated to form a plasma in a relatively small volume of the atmosphere of the reactor chamber, just above a suitable substrate holder located in the reactor chamber. The reaction of the components of the atmosphere then occurs in a relatively small plasma region, in which the strong local electric field of the microwave energy in the chamber ionizes the working gas to form diamond material, and the deposition of the diamond material occurs on a suitable substrate supported on a substrate holder. The substrate holder is typically arranged to move vertically in the chamber, thereby also allowing the resonant characteristics of the resonant cavity to be adjusted. This can be beneficial for higher density plasmas that tend to reflect a portion of the incident radiation, which in turn affects the resonant characteristics of the cavity.

[0004] Some documents with teachings related to microwave energy and MPCVD reactors are:

[0005] - A. Kromka et al., Linear antenna microwave plasma CVD deposition of diamond films over large areas, January 27, 2012, No. 6, Vol. 86, pp. 776-779;

[0006] - S. Liao et al., Synthesis, Simulation and Experiment of Unequally Spaced Resonant Slotted-Waveguide Antenna Arrays Based on the Infinite Wavelength Propagation Property of Composite Right / Left-Handed Waveguide, IEEE Transactions on Antennas and Propagation (Volume 60, Issue 7, July 2012);

[0007] -J. Kim et al., Large-area surface wave plasmas using microwave multi-slot antennas for nanocrystalline diamond film deposition, Plasma Sources Science and Technology, No. 1, Vol. 19;

[0008] - Microwave engineering of plasma-assisted CVD reactors for diamond deposition, Journal of Physics Condensed Matter (impact factor: 2.35), September 2009; 21(36): 364202, DOI: 10.1088 / 0953-8984 / 21 / 36 / 364202; - J.-H. Hur et al., US2005 / 0160986A1, July 28, 2005;

[0009] -L. Xiao Jing et al., IC3ME 2015 (pp. 2170-2176);

[0010] - JEPinneo, US5230740A, July 27, 1993;

[0011] - AH Gicquel et al., US 2006 / 0153994A1, July 13, 2006;

[0012] -CN 103526187A, Wuhan University of Technology, January 22, 2014.

[0013] -YA Lebedev, Microwave discharges at low pressures and peculiarities of the processes in strongly non-uniform plasma, Plasma Sources Sci. Technol., 24053001, 2015, reviews methods of microwave plasma generation using centimeter-millimeter wavelength microwaves at pressures from approximately 10-2 to 30 kPa based on scientific publications from 1950 to the present.

[0014] - US2005 / 000446 A1 relates to a plasma processing device, which includes: at least one electromagnetic wave source for generating electromagnetic waves; an electromagnetic wave distribution waveguide part for distributing the electromagnetic waves generated from the electromagnetic wave source; a plurality of waveguides, each waveguide being coupled to the electromagnetic wave distribution waveguide part, the waveguides being arranged on the same plane; a plurality of slits arranged in each of the waveguides; at least one electromagnetic wave radiation window arranged to face each of the slits; and a vacuum container, in which plasma is generated by the electromagnetic waves radiated from the electromagnetic wave radiation window.

[0015] - EP 0702393 A2 discloses a plasma processing device, which includes: a plasma chamber having a narrow window; and a rectangular waveguide for coupling with the plasma chamber, the rectangular waveguide having a long slot, the long slot being arranged in the E plane of the rectangular waveguide to be opposite to the narrow window of the plasma chamber and extending along the waveguide axis direction of the rectangular waveguide. At least two long slots are also arranged in at least one rectangular waveguide.

[0016] -KR 20170101452 A relates to a surface wave plasma device, which includes: a first waveguide, the first waveguide including a plurality of slot antennas connected to a first microwave energy source on one end; a second waveguide, the second waveguide including a plurality of slot antennas, the second waveguide being arranged in parallel with the first waveguide, the second waveguide having a second microwave energy source connected to an opposite end of the first waveguide; a dielectric plate, the dielectric plate introducing microwaves radiated from the slot antennas into a chamber to generate surface wave plasma; and a gas supply portion, the gas supply portion supplying gas into the chamber.

[0017] The above MPCVD reactors have limited deposition areas, and therefore a large-area, energy-efficient plasma chemical vapor deposition reactor apparatus is required. Summary of the invention

[0018] According to the present invention, a new large area microwave plasma chemical vapor deposition (LA MPCVD) reactor equipment design is proposed.

[0019] The present invention provides a LAMPCVD reactor apparatus comprising a Composite Right / Left-Handed (CLRH) waveguide section according to independent claim 1.

[0020] The invention is also a method according to independent claim 16 for providing large area plasma chemical vapor deposition in a reactor chamber.

[0021] The LAMPCVD and methods of the present invention allow for uniform thin film deposition over large areas on different substrates.

[0022] An example of application of a reactor according to the invention makes it possible to scale the size of the reactor chamber to increase the size of the area of ​​the generated plasma, thereby allowing, for example, standard-sized wafers to be diamond coated. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to illustrate the principles, operation and advantages of the present invention, embodiments of the present invention will now be described in further detail with reference to the following drawings. Please note that in order to better illustrate the microwave characteristics, several of the drawings show the cavity, that is, the interior space of the element, rather than the physical element itself. This makes it easier to visualize the cavity itself and the electric field distribution within the cavity.

[0024] Figure 1 A perspective view of the cavity of a composite right / left-handed CRLH waveguide according to an embodiment of the present invention is shown.

[0025] Figure 2 Shows Figure 1 The current density on the top surface of the cavity.

[0026] Figure 3 1 is another top view of a coupler showing a typical configuration and a cavity and principle of a homogeneous current density distribution of a second example of a LAMPCVD reactor device according to the present invention, wherein the LAMPCVD reactor device uses a plurality of short-circuited CRLH waveguides arranged side by side with slots for coupling microwave energy from the waveguides. It should be noted that only the cavity of the CRLH waveguide is shown, and no physical device is shown.

[0027] Figure 4a A resonant cavity according to an embodiment of the present invention is shown in a 3D CAD model, which is connected to a Figure 3 A set of CRLH waveguides is shown. Only the cavity is shown here.

[0028] Figure 4b Shows Figure 4a The electric field distribution in the yz-plane and xz-plane of the resonant cavity is shown in . It can be seen that the electric field is high throughout the volume of the resonant cavity.

[0029] Figure 5 The magnetic field distribution in the yz direction is shown. The arrows here represent both the direction and the field strength. Larger and thicker arrows represent greater field strengths than smaller and thinner arrows.

[0030] Figure 6 Shown for Figure 4a Cross section of the reactor and electric field distribution in the xy-plane, xz-plane and yz-plane of the embodiment in FIG. The solid red lines represent the walls of the deposition chamber, the dotted black outline represents the quartz window, and the dashed black outline represents the deposition area.

[0031] Fig. 7A A 3D CAD model of a resonant cavity according to the present invention is shown, the resonant cavity being connected to a Figure 3 A set of CRLH waveguides shown in FIG. 1 . Note that only the cavity is shown here. Here, the reactor cavity is divided into two main volumes, a first sub-chamber and a second sub-chamber, which in this example correspond to the lower volume and the upper volume, respectively.

[0032] Figure 7B Provide the basis Fig. 7A 0 is a perspective view of a cutaway depiction of a three-dimensional illustration of the electric field inside a LAMPCVD reactor device according to an embodiment of the present invention shown in FIG.

[0033] Figure 8 Shows Fig. 7A Magnetic field distribution in the yz direction of an embodiment of the resonant cavity in . Here the arrows represent both direction and field strength, with larger and thicker arrows representing greater field strength than smaller and thinner arrows.

[0034] Fig. 9 The cross-sectional view shows Fig. 7A Electric field distribution in the yz-plane for an embodiment in FIG. The dotted black outline represents a possible position of the quartz window.

[0035] Fig. 10A 7 is a perspective view showing the electric field at a given moment in the cavity of a LAMPCVD reactor device including four CRLH waveguide devices with short ends arranged side by side and an arrangement of waveguide wires and shunts arranged to supply microwave energy from a common microwave energy source to all CRLH waveguide devices, such as a T-junction. A horizontally arranged quartz window is also shown.

[0036] Fig. 10B It shows Fig. 10A 3D diagram of the physical implementation of the embodiment in FIG. Here, the LAMPCVD reactor includes four CRLH waveguide devices with shorted ends arranged side by side under the vacuum chamber and an arrangement of waveguides and shunts, such as T-junctions, arranged to supply microwave energy from a common microwave energy source to all CRLH waveguide devices, which will be connected to the rectangular input port at the bottom of the figure. An impedance matching unit, such as a 3-stub tuner, can be used between the energy source and the input port.

[0037] Fig.11 The electric field distribution in the xz plane is shown in cross section. The dashed outline indicates the plasma region. This distribution can represent Figure 4a distribution of the embodiments shown in, or Fig. 7A Implementation method, the second sub-chamber, and the distribution of the upper volume of the reactor chamber.

[0038] Fig. 12A is based on Fig. 7A Schematic cross-sectional view of a detail of a reactor of the embodiment shown in FIG.

[0039] Fig. 12B It is shown Fig. 10B A perspective view of the physical implementation of the upper half of the reactor vacuum chamber shown in FIG. In this figure, the front panel has been removed to show the upper Fig. 12A Details of the reactor shown in .

[0040] Fig.13A It is a three-dimensional diagram of the unit cell cavity of the CRLH waveguide.

[0041] Fig. 13B is a scatter diagram showing the phase shift per unit cell at a frequency of 2.45 GHz.

[0042] Fig. 13C The dimensions of the unit cell cavity according to an embodiment of the present invention are shown in mm when the frequency is 2.45 GHz.

[0043] Fig.13D The size and arrangement of the slots of a CRLH waveguide according to an embodiment of the present invention are shown. In this embodiment, the slots are arranged at 45 degrees relative to the z-direction and x-direction of the waveguide and have a length of 40 mm and a width of 8 mm.

[0044] Fig.14A Shows how the short lines can be used to adjust the size of the unit cell. Remember that the unit cell shown is the cavity, and the short lines represent the physical elements.

[0045] Fig. 14B The cross-sectional view with the top cut off shows how a short wire can be inserted into the cavity to change the size of the unit cell. Here, the physical implementation of a CRLH waveguide according to the invention is shown. A cavity is a continuously arranged unit cell arranged inside a waveguide.

[0046] Fig. 14C Shows Fig. 14B details.

[0047] Fig.15 An embodiment of a method for adapting a reactor to different operating frequencies is shown in a block diagram, wherein the operating frequency deviates from a nominal frequency for which the reactor is designed.

[0048] In the drawings, the x-direction and the y-direction are defined as being perpendicular to the CLRH waveguide, while the z-direction is in the longitudinal direction of the waveguide. In addition, the y-direction is the direction from the waveguide to the reactor. Directions are indicated in most of the figures. The definitions of directions are for illustration only, and other definitions may be used instead.

[0049] The drawings of the application are filed in color. This improves the illustration of current distribution in the reactor and its elements, such as, for example, the current distribution in the CLRH waveguide section. Red represents the highest current density, while blue is the lowest current density. Between red and blue are orange, yellow and green areas with decreasing current density. For example, along Figure 2 and Figure 3 The center of the CLRH section, Figure 7B and Fig. 9 in the center of the top chamber, and in Fig.11 In the center, red can be seen, and therefore the highest current density can be seen.

[0050] Detailed description of the invention

[0051] Hereinafter, the present invention is referred to as a large area microwave plasma chemical vapor deposition reactor and is identified herein by the acronym LAMPCVD. In general, the LAMPCVD of the present invention provides a new coupling of microwave energy in a large area deposition chamber in a first aspect. Figure 3 As shown in , the microwave energy coupler is at least a section based on the infinite wavelength property of a composite right / left-handed CRLH waveguide. The CRLH waveguide device can be a short-circuited section of a CRLH waveguide, composed of a chain of waveguide unit cells. Each unit cell in the chain is designed to provide a phase shift for the left-handed LH and the right-handed RH, providing a passband with zero dispersion for a frequency that matches the operating frequency of the microwave energy. Typically, in a practical implementation, the microwave energy generator can operate at a frequency of 2.45 GHz. In the application of this property of the CRLH waveguide operating at its "infinite wavelength propagation frequency", the currents in different parts of the wall of the waveguide appear uniform or "coherent" at any distance, without significant changes in the direction of microwave propagation in the longitudinal direction indicated by the axis marked by "z" in the waveguide, and extend over substantially the entire length of the short-circuited section of the CRLH waveguide included in the CRLH waveguide device of the present invention.

[0052] In order to couple apparently uniform or "infinite wavelength", "coherent" electromagnetic microwave energy out of the waveguide and into the LAMPCVD reactor chamber, the CRLH waveguide device of the present invention is provided with one or more appropriately sized and oriented slots in the wall of the CRLH waveguide, which carry uniformly distributed "coherent" currents established by microwave energy propagating in the waveguide. In this way, all slot elements along the short-circuited CRLH waveguide wall can be excited to output microwave energy that is in phase or anti-phase in time.

[0053] In order to also expand the area of ​​the uniform electric field in a direction different from the direction of microwave energy propagation in the CRLH waveguide of a single CRLH waveguide device of the present invention, such as, for example, in the direction indicated by the axis marked "y", several CRLH waveguide devices can be positioned in a side-by-side configuration and these CRLH waveguide devices work simultaneously to establish a large-area uniform microwave energy electric field in the reaction chamber, thereby establishing a large-area uniform plasma region.

[0054] Therefore, in a first embodiment, the present invention is a LAMPCVD reactor device (1). The reactor device (1) comprises a reactor chamber (2), which is suitable for providing a plasma region in the interior of the reactor chamber by electromagnetic energy of a first frequency. The reactor device (1) also comprises a CRLH waveguide segment (3), which is suitable for operating at the first frequency at infinite wavelength, and the CRLH waveguide segment (3) has a coupling device (4) in the wall, which is arranged to couple electromagnetic energy from the interior of the CRLH waveguide segment (3) to the interior of the reactor chamber (2). Figure 4a and Fig. 7A Two different reactor devices are shown indirectly through the inner cavity of the reactor device. Fig. 10B Shows that there is Fig. 7A The reactor device (1) has an inner cavity. Figure 1 Schematic diagram of a CRLH waveguide segment that can be used to illustrate a CRLH waveguide cavity according to the present embodiment.

[0055] In a related embodiment, the coupler arrangement comprises a plurality of electromagnetic energy couplers spaced apart relative to one another.The coupler arrangement may comprise a slot in a wall of the CRLH waveguide section.

[0056] In a related embodiment, one or more CRLH waveguides in the CRLH waveguide section have a second end that is short-circuited.

[0057] The above LAMPCVD reactor apparatus may include an electromagnetic energy source having an energy output, and wherein one or more CRLH waveguides in the CRLH waveguide section have a first energy input end coupled to the energy output of the electromagnetic energy source.

[0058] A tuning device may be connected between the energy output and the energy input.

[0059] like Figure 3 As shown in , one or more CRLH waveguides in the CRLH waveguide section may have a short-circuited second end. The short-circuited end here is opposite to the first energy input end.

[0060] In e.g. Fig. 7A In the second embodiment shown in , the reactor chamber comprises a first sub-chamber and a second sub-chamber, wherein the first sub-chamber comprises a coupler device and the second sub-chamber is adapted to comprise a plasma region. Electromagnetic energy is provided from the CRLH waveguide section via the first sub-chamber to the second sub-chamber. Other elements except the reactor chamber may be the same as in the first embodiment.

[0061] The first subchamber and the second subchamber may have the same cross-sectional area.

[0062] The second sub-chamber may include a quartz window arranged to separate the plasma region from atmospheric pressure.

[0063] The first subchamber and the second subchamber may be arranged on top of each other and as Fig. 7A As shown in , they can be connected to each other at each end.

[0064] The electromagnetic energy may be microwave energy at a first frequency, wherein, in a related embodiment, the first frequency may be 2.45 GHz.

[0065] The LAMPCVD reactor apparatus may include one or more CRLH waveguides.

[0066] In a third embodiment, which may be combined with any of the above embodiments, the CRLH waveguide segment comprises Figure 3 Multiple CRLH waveguide sections are arranged side by side as shown in FIG.

[0067] In a fourth embodiment which may be combined with any of the above embodiments, the LAMPCVD reactor apparatus of any of the above claims, wherein the CRLH waveguide segment comprises periodically cascaded unit cells.

[0068] In a related embodiment, the unit cell relationship between frequency and phase shift may be configurable.

[0069] In order to configure the unit cell, the unit cell in a related embodiment includes a tuning element configured to change the internal dimensions of the unit cell. The tuning element may be, for example, Fig.14A , Fig. 14B and Fig. 14C The arrangement shown in is a pair of short lines inserted into each unit cell.

[0070] In one embodiment, the present invention is a method for providing large area plasma chemical vapor deposition in a reactor chamber, wherein the reactor chamber is arranged to provide a plasma region in the interior of the reactor chamber by electromagnetic energy at a first frequency. The method comprises coupling electromagnetic energy from the interior of a CRLH waveguide segment to the interior of the reactor chamber via a wall coupler arrangement of the CRLH waveguide segment, wherein the CRLH waveguide segment is arranged to operate at the first frequency at infinite wavelength. The wall coupler arrangement here may be, for example, Figure 3 The gap shown in .

[0071] In one embodiment, the CRLH waveguide section includes periodically cascaded unit cells.

[0072] In a related embodiment, the unit cell may include a tuning element configured to change an internal dimension of the unit cell, wherein the method includes adjusting the tuning element.

[0073] In a related embodiment, an electromagnetic energy source having an energy output is connected to an input of a CRLH waveguide section, wherein the method includes minimizing measured reflected power by iteratively adjusting a tuning element and impedance matching the electromagnetic energy source to the CRLH waveguide section.

[0074] The tuning element may be, for example, Fig.14A , Fig. 14B and Fig. 14C The short line shown in .

[0075] Furthermore, the reactor chamber and CRLH waveguide section of the method may include features from any of the embodiments for the above LAMPCVD reactor. DETAILED DESCRIPTION

[0076] In the following, embodiments of the present invention will be described with reference to the accompanying drawings. In general, the embodiments describe a LAMPCVD reactor comprising a plurality of CRLH waveguides positioned adjacent to each other, such as Figure 3 Four waveguides are shown in FIG. Figure 3 All four waveguides shown in are placed in such a way that the magnetic current vectors point in the same direction.Other configurations consisting of any number of CRLH waveguides positioned adjacent to each other may be used.

[0077] The resonant cavity is placed on top of the CRLH waveguide. Figure 4a A 3D CAD model of the corresponding resonant cavity on top of four CRLH waveguides is shown. The size of the resonant cavity is determined by the area occupied by the radiating slots. The height h of the chamber is chosen to be approximately half the wavelength of the microwave radiation coupled into the cavity. It is important to note that the size of the LA MPCVD reactor resonant cavity can be scaled by simply changing the length and number of CRLH waveguides, i.e. changing the area occupied by the radiating slots.

[0078] Microwave radiation is magnetically coupled into the resonant cavity. Figure 5 It is shown in Figure 4a A cross-sectional view of the resonant cavity depicted in the yz plane, wherein the arrows indicate the direction and strength of the magnetic field induced by the radiating slot element.

[0079] The alternating magnetic field generates a uniform electric field in a direction perpendicular to the magnetic field across a large area of ​​the resonant cavity, such as Figure 4b The cross-sections of the electric field distribution in the xy-plane, xz-plane, and yz-plane are shown in Figure 6 as shown in .

[0080] The uniform electric field ionizes the working gas and produces a uniform plasma over a large area, see Figure 6 The deposition chamber of the reactor must be separated from the atmospheric pressure. This is achieved by placing a quartz window above the radiation element. However, there are some limitations to placing the quartz window close to the plasma region. First, a large area cavity requires a large quartz window. In order to withstand the atmospheric pressure, the thickness of the window increases with the area. As a result, by increasing the cavity area, the surface of the window becomes closer to the plasma region. Second, the hot plasma generates a high heat load on the window and can damage it. Thermal damage on the window can be avoided by reducing the operating pressure in the chamber to the sub-millibar range, thereby limiting the deposition temperature of the chemical vapor deposition process.

[0081] In order to overcome this problem, another design of the resonant cavity is proposed. The new cavity is composed of a bottom volume and a top volume or a first sub-chamber and a second sub-chamber connected to each other, such as Fig. 7A Each volume has height h and can occupy Figure 4a The distance between the two volumes can vary from 130 mm to 170 mm. Selecting different inter-volume distances produces different electric field distributions in the top and bottom parts.

[0082] Fig. 7A The 3D CAD model of the resonant cavity is shown. The cross-section of the electric field distribution in the yz-plane and the xz-plane is shown in Figure 7B as shown in .

[0083] like Figure 8 As shown in FIG. 1 , microwave radiation is magnetically coupled into the bottom volume or first subchamber in a similar manner to previous resonant cavity designs. The electromagnetic waves propagate further upward through the connecting waveguide to the top volume or second subchamber, thereby generating a Figure 5 Similar magnetic field strength patterns as shown in .

[0084] In the above embodiments, the resonant cavity arranged above the CRLH waveguide section has been shown. However, the resonant cavity may also be arranged, for example, below the CRLH waveguide or at the side of the CRLH waveguide.

[0085] The corresponding dimensions of height, width and length of the resonant cavity and the corresponding first and second sub-chambers, as well as the relative dimensions between the first and second chambers, and the distance between the first and second chambers may also vary as long as they operate at the first frequency.

[0086] The CRLH waveguide or the waveguides in a CRLH waveguide section may also have different configurations. For this purpose, any waveguide design, for example curved, with unit cells of the type specified above may be used. In addition to short-circuits, the waveguides may be connected to each other, for example in series.

[0087] The coupler means, for example one or more slots in the CRLH waveguide, may be arranged on any wall, ie the side wall, the top wall or the bottom wall of the CRLH waveguide.Preferably, in order to facilitate an enlarged plasma region in the resonant cavity, the field density distribution is longitudinal.

[0088] The resonant cavity design consisting of a bottom volume and a top volume overcomes the problem of a large quartz window. The quartz window can now be placed in several locations away from the hot plasma, such as Fig. 9 The dashed outline shows the vertical and horizontal positions of the quartz window. The position is intentionally chosen where the electric field is minimal. The complete configuration of the LA MPCVD reactor with horizontally positioned quartz windows is shown in Figure 10. Four CRLH waveguides are connected using a set of T-junctions and excited using one waveguide port.

[0089] An embodiment of a CRLH waveguide will now be described. This embodiment can be combined with any of the above embodiments.

[0090] The coupling of microwave radiation inside the resonant cavity of a LA MPCVD reactor can be achieved using a set of slotted composite right / left-handed (CRLH) waveguides, each with infinite wavelength propagation properties. This allows the generation of uniform high-intensity electric fields over a large area inside the cavity. The theory of CRLH transmission lines can be found, for example, in the following literature:

[0091] - A. Lai et al., Composite right / left-handed transmission line metamaterials, IEEE Microwave Magazine, (Volume 5, Issue 3, September 2004).

[0092] -Amr M. Nour Eldeen and Islam A. Eshrah, CRLH Waveguide with Air-Filled Double-Ridge Corrugations, 2011 IEEE International Symposium on Antennas and Propagation (APSURSI).

[0093] -T. Ueda et al., Dielectric-Resonator-Based Composite Right / Left-Handed Transmission Lines and Their Application to Leaky Wave Antenna, IEEE Transactions on Microwave Theory and Techniques, (Vol. 56, No. 10, October 2008).

[0094] - L. Shaowei et al., Left-Handed Transmission Line Based on Resonant-Slot Coupled Cavity Chain, IEEE Microwave and Wireless Components Letters, Vol. 17, No. 4, April 2007).

[0095] -Y. Chen et al., Unequally Spaced and Excited Resonant Slotted-Waveguide Antenna Array Based on an Improved Resonant-Slot Coupled Cavity Chain Composite Right / Left-Handed Waveguide, Progress in Electromagnetics Research, 2010, 110: 421-435.

[0096] The CRLH waveguide consists of a periodically cascaded chain of unit cells. Each unit cell has the unique property of supporting left-handed (LH) and right-handed (RH) wave propagation, which can be represented using an equivalent circuit model as described above by Ueda et al. In the balanced case, the unit cell has no stop band and seamlessly transitions from the LH to the RH band in the dispersion diagram. Since the proposed invention uses the infinite wavelength propagation property of the CRLH waveguide, each unit cell in the waveguide must be balanced. This criterion can be met by different designs of the unit cells, for example, using designs as proposed in the literature by Elden and Esrah, Uead et al., Shaowei and Chen et al. above.

[0097] The current implementation of the CRLH waveguide employs a design similar to the unit cell as described by Chen et al. Fig.13A The unit cell shown is designed in such a way that Fig. 13B The dispersion diagram shown has a seamless transition from the LH to RH bands and thus the unit is balanced. Fig. 10B It can be seen that the infinite wavelength propagation frequency is 2.45 GHz and matches the operating frequency of the energy source or microwave generator.

[0098] The unit cell can be implemented in various geometries and supports infinite wavelength propagation frequencies beyond 2.45 GHz.

[0099] The CRLH waveguide consists of a periodically cascaded array of unit cells and terminated at a metal wall, such as Figure 3 As shown. Microwave radiation to the CRLH waveguide is supplied through the transition waveguide. Due to the infinite wavelength propagation characteristics of the CRLH waveguide, the surface current along the waveguide (z direction) flows undisturbed, as shown in Figure 2 and Figure 3 As shown. Thus, compared to a conventional waveguide where adjacent slots are separated by half the waveguide wavelength (λg), the radiating slot elements for coupling microwave radiation into the cavity can be placed at almost any position and close to each other. Thus, a uniform electromagnetic field distribution over a large area can be achieved using the present invention.

[0100] The radiation mechanism of the slots is the same as in conventional waveguides, and the amount of radiation from each slot is determined by the intercepted current. As a result, the radiated power of the slot depends on the tilt angle relative to the corresponding center line of the CRLH waveguide. Here, all the slots are rotated 45 degrees to maximize the radiated power.

[0101] An effect of the invention is that the reactor chamber can be scaled up. This can be done by extending the CRLH waveguide as described above or adding more waveguides. This will effectively increase the size of the region of plasma produced.

[0102] Another effect is that a LA MPCVD according to embodiments of the present invention can operate above the sub-millibar pressure range, whereas other implementations of other LA MPCVD reactors, for example using standard waveguides, can only operate at lower pressures.

[0103] This is made possible by a novel coupling technique made possible by the CRLH waveguide, which produces a plasma with a fairly uniform and shallow shape throughout the deposition area compared to existing techniques. The height of the plasma is less than half the wavelength at 2.45 GHz, which means that the plasma can efficiently absorb the input microwave radiation. This results in a high absorbed power density that allows operation at higher pressures.

[0104] The unit cell may be designed in such a way that the phase shift per unit cell is zero for an operating frequency of 2.45 GHz.

[0105] In an embodiment that can be combined with any of the above embodiments, for frequencies other than 2.45 GHz or any other operating frequency, a phase shift per unit cell of zero can be achieved by changing the size of the unit cell. This is particularly important for microwave generators where the operating frequency is not locked and is a function of output power. Typically, the frequency of an industrial magnetron increases with increasing power and can deviate from the nominal frequency by the order of ±1%. Therefore, as the output power of the generator changes, the shape of the unit cell can actively adapt to the change in operating frequency.

[0106] In a related embodiment, the change in unit cell shape is achieved in such a way that the phase shift per unit cell is zero for any frequency.All units in one or more CRLH waveguides may be adapted simultaneously. Fig.15 A block diagram illustrating a method of adaptive control of a unit cell is shown in .

[0107] The method starts with setting the output power of the microwave generator and measuring the corresponding operating frequency. Next, the shape of all unit cells is changed by adjusting certain dimensions of the cell or inserting tuning elements such as stubs and keeping the cell balanced. The shape of each unit cell must be changed in the same way using input from simulation or empirical data. The frequency of the adjusted cell must match the operating frequency measured in the previous step. After adjusting the cell, the impedance observed by the generator can be matched with an impedance matching cell such as a 3-stub tuner placed between the energy source and the CRLH waveguide. The reflected power P measured in this step is ref is retained for later use. Since the input used for cell adjustment has an error, in the next step, the cell should be changed by a small amount compared to the adjustment in the third step. Next, match the impedance again and measure the corresponding reflected power P'ref Finally, compare P ref With P' ref If P' ref <P ref , the unit is changed again after the impedance matching step and a new reflected power measurement. These steps are repeated iteratively until the reflected power is minimized. If the output power of the generator is changed, the procedure is repeated again.

[0108] As shown in FIG. 14 , adaptive control of the unit cell can be achieved, for example, by inserting two (truncated) short wires simultaneously in the bottom portion of the unit. The unit cell can be described using an equivalent circuit model by decomposing the unit into a set of ripples, short wires and rectangular waveguides with corresponding parallel inductances, series capacitances, and series inductances and parallel capacitances. Therefore, inserting the (truncated) short wires into the unit effectively changes the inductance and capacitance of the unit element. As a result, the frequency corresponding to the phase shift per unit cell of zero changes. This allows adaptive control of each unit cell in one or more CRLH waveguides. The depth of the short wire insertion should be selected to match the operating frequency of the generator so that the surface current density of the waveguide remains uniform and unchanged. During this process, the unit cell should remain balanced.

[0109] Chemical vapor deposition (CVD) of diamond material can be achieved in the following ways. Figure 7B and Fig. 9 The uniform electric field shown in ionizes the working gas and produces a uniform plasma over a large area, as shown in Fig.11 as shown in .

[0110] Typical working gases for diamond CVD processes are hydrogen and methane. Methane is used as a carbon source, and atomic hydrogen dissociated from molecular gases by plasma is necessary for selectively etching graphite content in the process. Other gases such as nitrogen, oxygen or argon can be introduced into the chamber to change CVD process parameters, such as growth rate and substrate temperature. A schematic representation of an embodiment of a LA MPCVD reactor is shown in Figure 12. It is important to note that both the top and bottom surfaces of the provided chamber cavity, i.e., the second subchamber, can be used for the deposition process. Here, only the deposition process on the bottom surface is presented.

[0111] The working gas is introduced from the top of the second sub-chamber. The gas is delivered to the substrate using tubes positioned above the substrate. Each tube includes a set of holes for uniform gas distribution over the entire deposition area.

[0112] exist Fig. 12AThe central, plasma region is represented by the red oval. It covers the substrate stage represented by the magenta rectangle. Diamond material is deposited on a substrate placed on top of the stage. The substrate is heated by the plasma, but the stage can also be heated by RF induction or other means if necessary.

[0113] The process gas can be evacuated from the chamber using a vacuum pump. The pumping rate can be actively adjusted during the CVD process to keep the pressure stable.

Claims

1. A large-area microwave plasma chemical vapor deposition reactor device, the reactor device comprising: a reactor chamber adapted to provide a plasma region in an interior of the reactor chamber by electromagnetic energy of a first frequency; as well as a composite right / left-hand waveguide section adapted to operate at the first frequency at infinite wavelength and having a coupler arrangement in a wall arranged to couple electromagnetic energy from an interior of the composite right / left-hand waveguide section to an interior of the reactor chamber.

2. The large-area microwave plasma chemical vapor deposition reactor device according to claim 1, wherein: The coupler arrangement includes a plurality of electromagnetic energy couplers spaced apart relative to one another.

3. The large-area microwave plasma chemical vapor deposition reactor device according to claim 1 or 2, wherein: The coupler arrangement comprises a slot in the wall of the composite right / left-handed waveguide section.

4. The large-area microwave plasma chemical vapor deposition reactor device according to claim 1 or 2, comprising: An electromagnetic energy source having an energy output, and wherein one or more of the composite right / left hand waveguides in the composite right / left hand waveguide section has a first energy input end coupled to the energy output.

5. The large-area microwave plasma chemical vapor deposition reactor device according to claim 4, wherein: One or more of the composite right / left-hand waveguides in the composite right / left-hand waveguide section has a second end that is short-circuited.

6. The large-area microwave plasma chemical vapor deposition reactor device according to claim 1 or 2, wherein: The reactor chamber comprises a first sub-chamber and a second sub-chamber, wherein the first sub-chamber comprises the coupler arrangement and the second sub-chamber is adapted to comprise the plasma region, and wherein the electromagnetic energy is provided from the composite right / left-handed waveguide section via the first sub-chamber to the second sub-chamber.

7. The large-area microwave plasma chemical vapor deposition reactor device according to claim 6, wherein: The first subchamber and the second subchamber have the same cross-sectional area.

8. The large-area microwave plasma chemical vapor deposition reactor device according to claim 6, wherein: The second sub-chamber includes a quartz window arranged to separate the plasma region from atmospheric pressure.

9. The large-area microwave plasma chemical vapor deposition reactor device according to claim 6, wherein: The first subchamber and the second subchamber are arranged on top of each other and are connected to each other in each end.

10. The large-area microwave plasma chemical vapor deposition reactor device according to claim 1 or 2, wherein: The electromagnetic energy is microwave energy at the first frequency.

11. The large-area microwave plasma chemical vapor deposition reactor device according to claim 1 or 2, wherein: The first frequency is 2.45 GHz.

12. The large-area microwave plasma chemical vapor deposition reactor device according to claim 1 or 2, wherein: The composite right / left-hand waveguide section includes a plurality of composite right / left-hand waveguides arranged side by side.

13. The large-area microwave plasma chemical vapor deposition reactor device according to claim 1 or 2, wherein: The composite right / left-handed waveguide section comprises periodically cascaded unit cells, wherein the unit cell relationship between frequency and phase shift is configurable.

14. The large-area microwave plasma chemical vapor deposition reactor device according to claim 13, wherein: The unit cell includes a tuning element configured to change an internal dimension of the unit cell.

15. The large-area microwave plasma chemical vapor deposition reactor device according to claim 14, wherein: The tuning element includes a pair of short lines arranged to be inserted into the unit cell.

16. A method for providing large area plasma chemical vapor deposition in a reactor chamber, wherein: The reactor chamber is arranged to provide a plasma region in an interior of the reactor chamber by electromagnetic energy of a first frequency, wherein the method comprises: Electromagnetic energy is coupled from the interior of a composite right / left hand waveguide section to the interior of the reactor chamber via a wall coupler arrangement of the composite right / left hand waveguide section, wherein the composite right / left hand waveguide section is arranged to operate at the first frequency at infinite wavelength.

17. The method according to claim 16, wherein: The composite right / left-handed waveguide section comprises periodically cascaded unit cells, the unit cells comprising a tuning element configured to change an internal dimension of the unit cells, wherein the method comprises: The tuning element is adjusted.

18. The method according to claim 17, wherein: An electromagnetic energy source having an energy output is connected to an input of the composite right / left-handed waveguide section, wherein the method comprises: The measured reflected power is minimized by iteratively adjusting the tuning element and impedance matching the electromagnetic energy source to the composite right / left-handed waveguide section.

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