Radiant heated CVD reactor for superconductor manufacturing

Abstract

A radiant heater susceptor assembly used in a deposition reactor provides heat input and controls the temperature of a substrate tape as well as minimizes the build-up of errant deposition material. The radiant heater heats a substrate tape within the reactor upon which one or more thin films are deposited, particularly high temperature superconductor (HTS) thin films produced in a MOCVD reactor.

Description

Docket No.: RadHeater-WO RADIANT HEATED CVD REACTOR FOR SUPERCONDUCTOR MANUFACTURING CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority and benefit from U.S. Provisional Patent Application No.63 / 527,104 filed on July 17, 2023, entitled “A Radiant Heated Moving Susceptor MOCVD Reactor,” the content of which is incorporated in its entirety herein by reference. BACKGROUND OF THE INVENTION TECHNICAL FIELD

[0002] Embodiments of the subject matter disclosed herein generally relate to heater and susceptor assemblies utilized in a deposition reactor and more particularly in vapor deposition reactors for fabricating high-temperature superconductors on substrate tapes. DISCUSSION OF THE BACKGROUND

[0003] High temperature superconductors (HTS) provide the potential for development of superconductor components that perform at higher operating temperatures compared to traditional superconductors that operate at liquid helium temperature (4.2K). Superconductors operating at the higher temperatures thus provide the ability to develop superconducting components and products more economically. Thin film HTS material comprised of YBa2Cu3O7-x (YBCO), is one of aDocket No.: RadHeater-WO group of oxide-based superconductors. After the initial discovery of YBCO superconductors, other superconducting materials were discovered having a similar chemical composition but with Y replaced by other rare earth (RE) elements. This family of superconductors is often denoted as REBCO where RE may include Y, La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu. This material formed the basis for second generation or “2G” HTS wire technology which provides a more cost- effective material for manufacturing HTS tapes and wires.

[0004] Such HTS films are typically deposited as textured REBCO thin films which may include one or more buffer layers onto an atomically textured metal substrate. In the case of MOCVD, an organic ligand may comprise a vapor phase precursor delivered to the substrate for deposition. In the manufacturing of High Temperature Superconductors (HTS) via chemical vapor deposition (CVD) or metal- organic chemical vapor deposition (MOCVD) processing, a stainless steel or Hastelloy substrate tape is heated to high temperature, for example, 800oC to 900oC for the vapor phase precursor materials to deposit on the substrate tape and HTS film growth to occur.

[0005] Devices and methods for heating a substrate tape include hot block susceptors that directly contact the substrate tape and provide the needed heat via conduction. A typical CVD reactor apparatus 100 is shown in Fig.1 and includes using a single stationary hot block type susceptor 110 that supports and heats a translating substrate tape 120. (In this end view depiction, substrate tape 120 is translating perpendicular to the page.) Reactor housing 190 is maintained under vacuum conditions via an outlet port 130 and precursor reactant(s) 140 are introduced via a showerhead 150.Docket No.: RadHeater-WO

[0006] Existing heated susceptors in a CVD process particularly for HTS production have several disadvantages including high temperature gradients within the reactor, and errant deposition 180 that builds up on the exposed surfaces of the susceptor and other components of the reactor. The surface of the showerhead may be e.g., 300 – 350oC, while the surface of the deposition area may typically be around 850 – 900oC, making for very high temperature gradients of, for example, 500oC or more over the small gap between the showerhead and the top of the susceptor. The deposition process is thus very sensitive to temperature gradients and are preferably maintained within approximately a 5-10oC range of a target substrate temperature for acceptable deposition performance.

[0007] Thus, in a typical MOCVD HTS process, the reactant precursor gases tend to deposit upon other surfaces within the reactor chamber where the surface temperature is above approx.400–450oC. To keep the chamber clean, it is critical to maintain internal surfaces at a minimum, or at least below, approximately 400oC to prevent errant deposition which is deposition occurring on surfaces other than the intended substrate. Particularly in CVD reactors under vacuum, precursor vapor undergoes expansion and is thus prone to deposit on exposed surfaces of the susceptor outside the intended target deposition zone on the substrate tape where HTS film growth is desired. Over long process times, the errant material deposited on the susceptor may build up to exceed the tape thickness that may be between 30 to 100 micrometers (µm) thickness, for example. Such errant deposition buildup on susceptor surfaces near the tape edges themselves can cause degradation of the properties of the HTS film grown on the tape. For example, the precursor boundary layer flow uniformity on and around the tape may be impacted by errant deposition.Docket No.: RadHeater-WO The heat transfer and the radiation properties of the errant material build-up may thus be different than the HTS film which can cause local edge temperature non- uniformity on the tape; and / or the built-up material itself may break away, become entrained within micro-eddies, and redeposit on and foul or disturb the deposited layers. Such errant material may then negatively impact the performance characteristics of the HTS film, for example, degradation of critical current (Ic). Errant material build-up on the susceptor is also a major limiting factor in the ability to run continuous and lengthy HTS process runs. The build-up may prevent the reactor system from processing kilometers long HTS tapes due to a need to stop processing and disassemble the reactor for cleaning.

[0008] Another potential deleterious effect of the typical stationary hot block type susceptor setup is friction between the substrate tape translating across the top of the susceptor which results in stick-slip motion caused by small vibrations of the tape. This poor surface to surface contact can lower and cause greater variability on the tape temperature. This issue is more severe when the tape is thin, and the translation velocity is high.

[0009] For these reasons, new susceptor assemblies and reactor systems are needed to tightly control thermal conditions as well as minimize errant deposition particularly in areas proximal to the target substrate tape. In order to overcome the issues described above we have invented heater assembles, systems and methods where the tape is heated primarily, and in certain embodiments, solely by radiation.Docket No.: RadHeater-WO SUMMARY OF EXAMPLE EMBODIMENTS

[0010] According to an embodiment, there is a radiant heater assembly for heating and temperature control of one or more longitudinal substrate tapes within a deposition apparatus. The radiant heater assembly includes a longitudinal substrate tape that translates through a deposition zone within a deposition apparatus; a primary susceptor comprised of a radiant heater; a secondary susceptor disposed between the primary susceptor and the longitudinal substrate tape and which is configured as a longitudinal tape having a width greater than the longitudinal substrate tape. The secondary susceptor is supported by one or more refractory support elements which are disposed in between the primary susceptor and the secondary susceptor. The longitudinal substrate tape is disposed above the secondary susceptor by a predetermined vertical spacing without contacting the secondary susceptor.

[0011] According to another embodiment, there is a chemical vapor deposition (CVD) apparatus for deposition of thin films on a longitudinal substrate tape. The apparatus includes a reactor housing having an inlet showerhead for introducing a precursor and a vacuum exhaust, and a radiant heater assembly for heating and temperature control of one or more longitudinal substrate tapes within the reactor housing. The radiant heater assembly comprises a primary susceptor which is itself comprised of a radiant heater; and a secondary susceptor disposed between the primary susceptor and the longitudinal substrate tape with the secondary susceptor itself configured as a longitudinal tape having a width greater than the longitudinal substrate tape. The secondary susceptor is supported by one or more refractoryDocket No.: RadHeater-WO support elements which are disposed in between the primary susceptor and the secondary susceptor. The longitudinal substrate tape is disposed above the secondary susceptor by a predetermined vertical spacing without contacting the secondary susceptor. The longitudinal substrate tape is configured to translate above the secondary susceptor and below the inlet showerhead.

[0012] According to yet another embodiment, there is a chemical vapor deposition (CVD) apparatus for deposition of thin films on a longitudinal substrate tape. The apparatus includes a reactor housing having an inlet showerhead for introducing a precursor and a vacuum exhaust and a radiant heater for heating and temperature control of one or more longitudinal substrate tapes within the reactor housing. The radiant heater is positioned below the longitudinal substrate tape by a predetermined vertical spacing. The radiant heater heats the longitudinal substrate tape without contacting the longitudinal substrate tape.Docket No.: RadHeater-WO BRIEF DESCRIPTON OF THE DRAWINGS

[0013] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments. In the drawings:

[0014] FIG.1 shows a prior art CVD reactor assembly with a stationary hot block type susceptor.

[0015] FIG.2 shows a CVD reactor assembly with an exemplary susceptor assembly with a moving susceptor.

[0016] FIGS.3A and 3B show two views of an exemplary embodiment of a radiant heater for use in a CVD reactor that includes a primary susceptor with a secondary moving susceptor that does not contact the longitudinal substrate tape.

[0017] FIG.4 shows an exemplary embodiment of a radiant heater for use in a CVD reactor that includes a primary susceptor with a secondary moving susceptor without use of a radiant plate.

[0018] FIG.5A shows an embodiment whereby substrate support members comprised of short lengths of small diameter wires support the substrate tape(s).

[0019] FIG.5B shows another embodiment of substrate supports whereby L- shaped arms are utilized to the support substrate tape(s).

[0020] FIGS.6A-6D show additional embodiments with side tapes are disposed adjacent to the substrate tape(s) instead of underneath as the secondary moving susceptor.

[0021] FIG.7 shows an exemplary chemical vapor deposition (CVD) reactor apparatus that utilizes radiant heater assemblies described herein for controlling theDocket No.: RadHeater-WO temperature of one or more longitudinal substrate tapes as well as minimizing errant deposition.Docket No.: RadHeater-WO DETAILED DESCRIPTION OF EXAMPLES OF THE INVENTION

[0022] The following description of the embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to susceptor assemblies and systems for deposition of thin films, particularly superconducting coated conductors, formed from films deposited on substrate tapes in a CVD and more particularly in a MOCVD reactor. However, the embodiments discussed herein are not limited to such elements. For example, the susceptor assemblies disclosed herein have application to other reactor types and chemistries that utilize a susceptor for heating a substrate of any type, and where build-up of errant deposition may be a problem. Such other reactor types may include Pulsed Laser Deposition (PLD) and others.

[0023] Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. The drawings are intended to be illustrative of the claimed features and unless stated otherwise are not to scale. Where a dimension of a given feature may be pertinent, the detailed description will indicate one or more examples of the range and units of said dimension where needed toDocket No.: RadHeater-WO enable the subject matter. Further, the described features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

[0024] This disclosure describes various embodiments of a MOCVD reactor with radiant heater and susceptor assemblies for heating and temperature control of one or more longitudinal substrate tapes. In certain embodiments, the susceptor assembly includes a secondary moving susceptor that continuously provides a clean surface under and adjacent the substrate tape. Pending PCT Patent Application Publication WO / 2024 / 015275, entitled “Secondary Translating Susceptor Apparatus, System and Method” and co-owned by the present Applicant, discloses embodiments of a moving susceptor and the content is incorporated for all purposes herein by reference. Briefly recapitulating, the moving susceptor typically is comprised of a metal tape (e.g., a Hastelloy tape) that has a width at least equal to and preferably greater than the width of the substrate tape. In preferred embodiments, the metallic longitudinal substrate tape (i.e., the lengthy process tape upon which the desired HTS layer is to be deposited, which in certain embodiments may be 10 mm wide and meters or even kilometers in length) translates over and in contact with the moving susceptor thus the moving susceptor travels underneath the substrate tape.

[0025] An exemplary susceptor assembly 200 with a moving susceptor is illustrated in sideview in Fig.2. Susceptor assembly 200 is located inside reactor housing 190 which also includes a showerhead 150 and a vacuum exhaust 130. Susceptor assembly 200 includes a primary stationary susceptor block 210 and secondary moving susceptor 220 for heating and temperature control of aDocket No.: RadHeater-WO longitudinal substrate tape 120 within the deposition apparatus. Primary susceptor 210 is typically longitudinal in shape and thus has a length approximately equal to the desired deposition zone length within a reactor apparatus and a width equal to or slightly greater than the width of a substrate tape 120. Hence, the length of the primary susceptor is greater than its width, and typically is a length many times its width, e.g., 5, 10, 20 or more times its width. (In this sideview depiction of Fig.2, the substrate tape 120 translates parallel to the page.) Also, the upper surface of primary (stationary) susceptor block 210 as shown in Fig.2 may be curved in a lengthwise direction such that the vertical height 212 of the primary susceptor 210 is greater at the center so as to impart tension in both the moving susceptor 220 and the substrate tape 120 to improve contact between the two tapes. A curved primary susceptor 210 may also be used with or without a tensioning device (not shown) within the reel-to-reel system to further improve tension and contact.

[0026] Also in this embodiment, a wide tape acts as the secondary moving susceptor 220 and is supplied by one or more feed reels 250 on the left and translates over the primary stationary susceptor 210. Secondary susceptor tape 220 is then taken up by one or more take-up reels 260 on the right as shown. Note that the stationary susceptor 210 may also be referred to interchangeably as the primary susceptor, primary heater or primary heater element, primary susceptor block, fixed susceptor, main susceptor, or lower susceptor. Similarly, the moving susceptor 220 may also be referred to herein as the secondary susceptor, upper susceptor, secondary susceptor tape, or secondary tape. In the embodiments of susceptor assemblies disclosed herein, the term susceptor shall refer to a body of material configured to absorb energy and transmit it to a second body with the intent toDocket No.: RadHeater-WO provide a target temperature of a body. For example, the first body may absorb electromagnetic energy and convert it to heat which in turn may be transmitted to a second body by conduction or said heat of the first body may be re-emitted as infrared thermal or other wavelength of radiation and transmitted to a second body by radiation heat transfer, or the first body may directly absorb thermal energy and transmit it to another body by conduction.

[0027] Substrate tape 120 is also fed from one or more feed reels 265 and translates over moving susceptor 220 which in this embodiment is in contact with and translates over the primary stationary susceptor 210 after which substrate tape 120 is taken up by one or more take-up reels 270. Further, tensioning devices and payout and take-up reels for either the substrate tape(s) 120 or secondary moving susceptor tape(s) 220 may be located internal or external to the reactor housing 190. In this manner, the susceptor assembly 200 thus comprises a two-part susceptor (210 and 220) which includes an upper moving susceptor 220 in slidable contact with a lower non-moving susceptor 210. Thus, in this example, the primary susceptor 210 may be comprised of a conductive hot block type susceptor 110 such as that shown in Fig.1.

[0028] As mentioned above, longitudinal substrate tape 120 is typically comprised of a long thin tape wherein the length may be many meters or kilometers in length and the width comparatively narrow, e.g., 10 mm, 12 mm, etc. and may be fabricated from an atomically textured stainless steel or Hastelloy material. The moving susceptor 220 may also be comprised of stainless steel or Hastelloy but may also be composed of any suitably conductive metallic material such as copper, an alloyed metal or a conductive composite. Thus, the same or similar material used forDocket No.: RadHeater-WO the substrate tape may be used for the moving susceptor tape, but the two tapes may be comprised of different materials or compositions as well.

[0029] Also, substrate tape handling configurations described herein may encompass a “single-pass” tape configuration, or a single-length tape with “multi- pass” tape configuration, or several separate tapes running in parallel over susceptor assembly 200 in a “multi-track” configuration. The reels or rollers that are used in single or multi-pass configurations may be located inside the reactor, or outside the reactor with the one or more substrate tapes 120 passing through slits or ports in the reactor walls. U.S. Patent 11,910,726 and pending U.S. Patent Application 18 / 407,993 both entitled “Multi-Stack Susceptor Reactor for High-Throughput Superconductor Manufacturing” and co-owned by the present Applicant, describe various embodiments of tape handling configurations and the contents of both are incorporated herein in their entirety by reference.

[0030] Further improvements to the moving susceptor reactor and other reactor embodiments may incorporate a radiant heater to provide more consistent substrate temperature control while still minimizing the effects of errant deposited material which inhibit lengthy run time operation. Figure 3A illustrates an embodiment of a radiant heater for use in a CVD reactor that includes a primary susceptor with a secondary moving susceptor that does not contact the longitudinal substrate tape. In this example depicted as an end view, five longitudinal substrate tapes 120 are indicated but as mentioned, the substrate tape(s) may comprise a singular tape or a plurality of tapes of greater or less number. The radiant heater assembly 300 is comprised of a single or a plurality of radiant heater elements 310 as the primary susceptor which heats an optional radiant plate 320 positioned closelyDocket No.: RadHeater-WO above the heaters 310 in order to minimize the vertical gap, e.g., 1-3 mm, between heat source and target. Refractory support elements 330 may be narrow blocks of materiel composed of the same or similar material as the radiant plate 320 and are used to fix the vertical spacing between the radiant heater elements 310 and the radiant plate 320 and the moving susceptor 220. The radiant plate 320 may be composed of silicon carbide, a metal such as nickel, a metallic oxide, or metallic alloy such as Hastelloy and Haynes alloy. Thermocouples (not shown) may be inserted into or affixed to any aspect of the assembly including the heater element 310 or radiant plate 320 in order to measure the temperature and control the power supplied to the heaters. In the side view of Fig.3B, radiant heater elements 310 are shown positioned along the length of the substrate tape(s) 120 such that a main deposition zone is defined. The power to these heater element(s) can be programmatically controlled to obtain a uniform temperature along the deposition zone or a predetermined temperature profile. Additional zones on one or both ends of the main deposition zone may provide a region where the temperature is ramped up or ramped down from the main deposition zone temperature.

[0031] A second tape, which in preferred embodiments is wider than the substrate tape 120, forms a secondary moving susceptor 220 and is closely positioned above radiant plate 320, e.g., by a few mm or less, and below the longitudinal substrate tape Secondary moving susceptor 220 typically also translates in the same or opposite direction as the substrate tape translation, but at a lower speed, for example, at 1 / 10th the speed of the substrate tape. In the case of a plurality of substrate tapes 120, a single secondary moving susceptor tape 220 spanning the width of all the substrate tape may be utilized, however, it isDocket No.: RadHeater-WO contemplatable that more than one adjacent secondary moving susceptor tapes may be employed.

[0032] As discussed above, the same or similar material used for the substrate tape 120 may be used for the moving susceptor tape 220, however the two tapes may be comprised of different materials or compositions as well. In the case of a radiant heated moving susceptor, the susceptor 220 may ideally be composed of a material that has a high emissivity in the mid and far infra-red wavelength range at high temperature. Oxidized nickel, oxidized Hastelloy and oxidized Haynes alloy are possible choices. In addition, certain ceramic tapes which meet the emissivity requirement can also be used.

[0033] Moving susceptor 220 prevents significant quantities of precursor vapors coming in contact with the radiant plate 320 and heaters 310. However, an inert gas purge may be used to purge the space between the moving susceptor 220 and radiant plate 320 as well as between the radiant plate 320 and heaters 310 to further prevent any reagent vapors from entering these spaces.

[0034] In this radiant heated approach, errant particle accumulation on or adjacent the substrate tape is minimized as there is no contact between it and the moving susceptor. As mentioned, substrate tape(s) 120 may be positioned very closely above the moving susceptor 220, e.g., by one or a few millimeters, to allow for more efficient radiant heat transfer. Additionally, there is only a slight change in the emissivity of the moving susceptor 220 with time since the surface of the moving susceptor is renewed constantly. The radiant plate 320 assists in providing a uniform temperature across the width of the deposition zone. However, it is also possible to have additional radiant heaters 310 on the edges to adjust theDocket No.: RadHeater-WO temperature across the width. The substrate tape 120 temperature can be monitored and / or feedback controlled using pyrometers without contact, e.g., via viewing the tape through small holes in the showerhead or even other positions away from the susceptors and / or substrate tape. Controlling the substrate tape temperature directly by using pyrometers rather than indirectly by controlling the temperature of the radiant plate may be preferred since any process tape temperature change due to changes in the emissivity of the moving susceptor or gas flow will not be sensed by the thermocouples affixed or in radiant plate 320. Further, direct substrate temperature control vs the radiant plate likely will provide for the quickest response time for temperature correction. Thus, for more efficient heat transfer to the substrate tape(s) and improved temperature control, in other embodiments radiant plate 310 may not be used. Figure 4 (side view) gives such an embodiment of radiant heater assembly 300 without use of a radiant plate 320.

[0035] During operation, substrate tape 120 may sag which can cause variable vertical gap spacing 340 between the substrate tape and the moving susceptor 220 and can alter the amount of radiation incident on the underside of the substrate tape and thus contribute to deviations from the target temperature or temperature profile. For example, one meter length of 60 µm thick and 12 mm wide Hastelloy substrate tape 120 may sag by approximately 0.2 mm at the center. Thus, if the spacing between the substrate tape 120 and moving susceptor 220 is e.g., 4 mm, the change in radiation striking the process tape from one end to the center may be ~5 - 10%. The change in temperature due to this small variability can be readily compensated for by controlling the power supplied to the different zones of the heater(s) 310 which may include a particular profile down the length of theDocket No.: RadHeater-WO substrate tape that compensates for the effect of sag at the center. However, to obviate this potential issue related to the small sag, an alternative embodiment may employ structural elements to support the substrate tape 120 to better maintain a predetermined vertical spacing 340. Figure 5A depicts an embodiment whereby substrate support members 350 comprised of short lengths of small diameter (e.g., 1 mm) wires transverse perpendicularly on the underside of substrate tape(s) 120.

[0036] Depending on the length of the deposition zone, additional support wires may be spaced apart as needed, for example, every 10 centimeters, etc. Since the contact area between the very thin substrate support members 350 (e.g., wires of 1 - 2 mm diameter) and the substrate tape 120 is minimal, there should be minimal generation of stick-slip motion between the two components.

[0037] Other types of substrate support members 350 may include thin rods or cylinders, including hollow cylinders with a wire or second smaller diameter rod through the middle that permit a rolling action to further reduce friction. Another embodiment as shown in Fig.5B (end view) may comprise L-shaped arms 360 that also support substrate tape 120 being supported underneath by the short leg 365 of the “L” having minimal contact area with the substrate tape thereby minimizing friction. Other types of structural support elements, such as thin side rails running parallel and underneath substrate tape 120 or lateral siderails with grooves etc. and others are contemplatable by those skilled in the art having the benefit of the disclosure herein.

[0038] Figure 6A provides an alternate embodiment of a radiant heater assembly 600. In this example shown in end view, side tapes 610 are comprised of two or more tapes that run closely adjacent (e.g., 1 mm, or less lateral distance) toDocket No.: RadHeater-WO substrate tape(s) 120. In certain embodiments, a side tape 610 is present or translates one on each side of each substrate tape 120 instead of underneath as the secondary moving susceptor 220 as given in previous examples. In other embodiments, particularly single substrate tape 120 in multi-pass configurations, only two side tapes run adjacent the outer most substrate tape 120 windings. With this side tape 610 approach, errant deposited material 180 (not shown) collects on these side tapes 610. This removes the secondary moving susceptor 220 underneath the substrate tapes(s) 120 as a radiant sink in the system thereby allowing for more efficient radiant heat transfer to the substrate tapes 120. In the example of Fig.6A, optional radiant plate 320 supported by refractory support elements 330 above radiant heater 310 is shown employed as in previous examples. However, Fig.6b illustrates an embodiment without the use of a radiant plate.

[0039] Similar to prior examples, predetermined vertical gap 340 may be maintained by use of substrate and side tape support member 350 which are analogous to those discussed in reference to Figs 5A and B. However, with radiant heater assembly 600 embodiments, support member(s) 350 support both the substrate tape(s) 120 and side tapes 610. Exemplary Fig.6C shows one such embodiment of support member 350 used with side tapes 610 which for simplicity, radiant assembly 600 does not include radiant plate 320, but is understood that similar support schemes described above could be employed accordingly as well. For example, supports 350 may comprise a wire, rod, hollow cylinder with or without a central wire or axle oriented perpendicular to the substrate and side tapes 120 / 610, as well as parallel disposed rails or supports similar to support members 360 / 365 as described in reference to Fig.5B, but configured as sets of rails with a set of two orDocket No.: RadHeater-WO more to support the array of substrate and side tapes. Figure 6D shows an example of four rails 360 supporting a single substrate tape 120 and two side tapes 610.

[0040] An exemplary chemical vapor deposition (CVD) reactor apparatus 700 that utilizes radiant heater assemblies 300 / 600 described herein for controlling the temperature of one or more longitudinal substrate tapes 120 (four are shown) as well as minimizing errant deposition 180 is shown in Fig.7. In the example shown as an end view, CVD apparatus 700 includes reactor housing 190 which houses assembly 300 as described above and shown in Fig.3A. However, it is to be understood that any of the various susceptor assembly 300 / 600 embodiments described above and shown in Figs.3-6 may be installed into reactor apparatus 700 in a similar manner. Also, apparatus 700 is discussed with specific reference to a preferred embodiment of a MOCVD reactor for thin film production of HTS films. However, it is to be understood that other thin films and other deposition reactor types (e.g., CVD) may employ the radiant assemblies described herein.

[0041] The CVD apparatus 700 is comprised of a reactor housing 190 of a given length and width where typically the length is greater than the width and the housing 190 for HTS thin film depositions is preferably operated under vacuum conditions maintained by one or more exhaust or outflow ports 130. (The reactor’s lengthwise dimension is out of the page in the 2D representation of Fig.7.) A showerhead 150 for the delivery of one or more precursors 140, e.g., a metal organic compound from an external source (not shown) is included which may be a direct liquid injection vapor source, or a solid precursor feed system as disclosed in U.S. Patent 11,162,171 which is assigned to the present Applicant and incorporated by reference herein for all purposes.Docket No.: RadHeater-WO

[0042] In certain embodiments, illumination sources 160 are utilized to aid thin film growth on longitudinal substrate tape 120 and may be comprised of, for example, single or arrays of lamps, LEDs, etc. emitting one or more or a combination of Ultraviolet (UV) to visible wavelengths, but other wavelengths, such as near UV to far infrared bandwidth sources may be utilized. Illumination at the surface of the growing film energetically excites the surface atoms and enhances molecular surface mobility thus allowing for more rapid attainment of a lower energy configuration. In this manner, a photo-activated or photo-assisted deposition process enhances the YBCO deposition rate and improves the crystallization structure of the resulting HTS thin film. In the example of Fig.7, lamps 160 are positioned external the reactor housing 190 and the radiation transmitted through one or more windows 165 located on one or more walls of the reactor housing 190. In other approaches, lamps 160 may be located inside the reactor housing 190. However, minimizing the distance “d” between showerhead 150 and substrate tape(s) 120 has many advantages,including higher deposition rates and efficiency. Thus, in order to provide sufficient illumination through a small gap “d” necessitates an acute angle which favors 160 placement of radiations sources 160 at further distances. It is also preferred to place the radiation source outside the reactor housing 190 to prevent the illumination source from getting coated by errant deposition which would cause degradation of the illumination power and photo-activation effectiveness. Also, externally placed sources may more easily be cooled via water-to-water heat-exchanger. Hence external sources and use of windows 165 may be a preferred embodiment.

[0043] In such embodiments with reduced distance “d” between the susceptor and showerhead (e.g., as low as 20mm, 10mm, 5mm, or less) in particular areDocket No.: RadHeater-WO provided by the present disclosure of radiant heater assemblies 300 having a high degree of thermal control, owing in part to the heat transfer characteristics between the susceptor and proximally located showerhead 150. For example, reactor system 700 is thermally stable when it is connected to a heat source as well as a heat sink. The heat sink is the radiative heat transfer from the susceptor to the showerhead which is preferably cooled with fluid circulation, for example an oil or water circulation heat-exchanger maintained at, for example, 300 – 3500C and the source is the susceptor top surface and the HTS tape. Thus, stable heat transfer from the susceptor acting as the source to the showerhead acting as the sink across reduced distance “d” may aid in improving the temperature control over the HTS tape 120. Additionally, this effect may be further enhanced by selective application of emissivity adjusting coatings to various surfaces within the system, particularly the susceptors as well as the underside surface of the showerhead facing the primary or secondary moving susceptor.

[0044] Returning to the apparatus embodiment of Fig.7, radiant heater assembly 300 includes one or more radiant heater elements 310, radiant plate 320, refractory support elements 330, and secondary moving susceptor 220. In this example, four longitudinal substrate tapes 120 are positioned above secondary moving susceptor 220 by a predetermined vertical spacing 340. However, as discussed prior, the assembly 300 may be configured to heat any number of substrate tapes 120 and / or accommodate multiple passes of the same substrate tape or tapes. Substrate tape 120 payout and take-up reels (not shown) may be located inside the reactor or outside the reactor with the tape(s) passing through sealed ports located on the reactor walls of the housing 190.Docket No.: RadHeater-WO

[0045] CVD apparatus of Fig.7 shows heater assembly 300 configured as a radiant heater as primary susceptor 310 which may be connected to an electrical conduit or busbar 730 that may be located inside reactor housing 190 and ultimately connects to a power source 740 external the reactor. Power source 740 may be controlled by a control system 750 with a proportional integral derivative (PID) or other type of feedback controller capable of receiving inputs from one or more sensors 760 such as direct contact thermocouples or a non-contact infra-red pyrometer, comparing the measured temperature to a predetermined setpoint temperature, and adjusting the power input to the primary radiant heater 310 via power source 740.

[0046] CVD apparatus 700 may be further characterized by the additional features described herein to include but not limited to the following regarding either susceptor assembly 300 as discussed above and illustrated in Figs.2-7:

[0047] The refractory support element(s) 330 may be composed of a single or more than one component or material. The components of the refractory element(s) 330 may be further comprised of at least one material that is different from a material of another component.

[0048] One or more radiation shields may be applied to one or more portions of the susceptor assembly 300 or other reactor 700 components for purposes of redirecting or concentrating radiant energy.

[0049] The emissivity coating may be applied to one or more portions of the susceptor assembly 300 or to reactor apparatus 700 components e.g., the showerhead 150.Docket No.: RadHeater-WO

[0050] The emissivity coating may be a low emissivity or high emissivity coating, e.g., a ceramic or black body coating.

Claims

Docket No.: RadHeater-WO WHAT IS CLAIMED IS:

1. A radiant heater assembly (300) for heating and temperature control of one or more longitudinal substrate tapes (120) within a deposition apparatus, the radiant heater assembly (300) comprising: a longitudinal substrate tape (120) that translates through a deposition zone within a deposition apparatus; a primary susceptor comprised of a radiant heater (310); a secondary susceptor (220) disposed between the primary susceptor (210) and the longitudinal substrate tape (120) and configured as a longitudinal tape having a width greater than the longitudinal substrate tape (120); and wherein the secondary susceptor (220) is supported by one or more refractory support elements (330) disposed in between the primary susceptor (210) and the secondary susceptor (220); and wherein the longitudinal substrate tape (120) is disposed above the secondary susceptor (220) by a predetermined vertical spacing (340) without making contact with the secondary susceptor (220). 2 The radiant heater assembly of Claim 1, wherein the primary susceptor (310) is stationary and the secondary susceptor (220) translates across the top of the primary susceptor and underneath the longitudinal substrate tape (120) in a lengthwise direction relative to the longitudinal substrate tape (120).Docket No.: RadHeater-WO 3. The radiant heater assembly of Claim 1 further comprising a radiant plate (320 ) disposed between the primary susceptor (310) and the secondary susceptor (220).

4. The radiant heater assembly of Claim 3, wherein the radiant plate (320) is separated by a vertical gap maintained by one or more refractory support elements (330).

5. The radiant heater assembly of Claim 1, wherein the longitudinal substrate tape (120) is supported underneath by a substrate support member (350) configured to maintain the predetermined vertical spacing (340).

6. The radiant heater assembly of Claim 5, wherein the substrate support member (350) is comprised of one or more wires.

7. The radiant heater assembly of Claim 1, wherein the radiant heater assembly is configured to heat more than one longitudinal substrate tape (120).

8. A chemical vapor deposition (CVD) apparatus (600) for deposition of thin films on a longitudinal substrate tape (120), the apparatus (600) comprising: a reactor housing (190) having an inlet showerhead (150) for introducing a precursor (140) and a vacuum exhaust (130); a radiant heater assembly (300) for heating and temperature control of one or more longitudinal substrate tapes (120) within the reactor housing (190), wherein theDocket No.: RadHeater-WO radiant heater assembly (300) comprises a primary susceptor (310) comprised of a radiant heater; a secondary susceptor (220) disposed between the primary susceptor (310) and the longitudinal substrate tape (120) and configured as a longitudinal tape having a width greater than the longitudinal substrate tape (120); and wherein the secondary susceptor (220) is supported by one or more refractory support elements (330) disposed in between the primary susceptor (310) and the secondary susceptor (220); and wherein the longitudinal substrate tape (120) is disposed above the secondary susceptor (220) by a predetermined vertical spacing (340) without making contact with the secondary susceptor (220); and wherein the longitudinal substrate tape (120) is configured to translate above the secondary susceptor (210) and below the inlet showerhead (150).

9. The CVD apparatus of Claim 8, wherein radiant heater assembly (200) primary susceptor (310) is stationary and the secondary susceptor (220) translates across the top of the primary susceptor and underneath the longitudinal substrate tape (120) in a lengthwise direction relative to the longitudinal substrate tape (120).

10. The CVD apparatus of Claim 8, wherein the radiant heater assembly (300) further comprises a radiant plate (320) disposed between the primary susceptor (310) and the secondary susceptor (220).Docket No.: RadHeater-WO 11. The CVD apparatus of Claim 10, wherein the radiant plate (320) is separated by a predetermined vertical spacing (340) maintained by one or more refractory support elements (330).

12. The CVD apparatus of Claim 8, wherein the longitudinal substrate tape (120) is supported underneath by a substrate support member (350) to maintain the predetermined vertical spacing (340).

13. The CVD apparatus of Claim 12, wherein the substrate support member (350) is comprised of one or more wires.

14. The CVD apparatus of Claim 8, wherein the radiant heater assembly (300) is configured to heat more than one longitudinal substrate tape (120).

15. The CVD apparatus of Claim 8, further comprising an illumination source (160) located internal or external the reactor housing (190).

16. The CVD apparatus of Claim 15, wherein the illuminated source (160) is located exterior the reactor housing (190).

17. A chemical vapor deposition (CVD) apparatus (600) for deposition of thin films on a longitudinal substrate tape (120), the apparatus (600) comprising: a reactor housing (190) having an inlet showerhead (150) for introducing a precursor (140) and a vacuum exhaust (130);Docket No.: RadHeater-WO a radiant heater (310) for heating and temperature control of one or more longitudinal substrate tapes (120) within the reactor housing (190), and wherein the radiant heater is positioned below the longitudinal substrate tape (120) by a predetermined vertical spacing (340); and wherein the radiant heater heats the longitudinal substrate tape (120) without contacting the longitudinal substrate tape (190).

18. The CVD apparatus of Claim 17 further comprising a radiant plate (320) disposed between the radiant heater (310) and the longitudinal substrate tape (120).

19. The CVD apparatus of Claim 17, wherein the longitudinal substrate tape (120) is supported underneath by a substrate support member (350) to maintain the predetermined vertical spacing (340).

20. The CVD apparatus of Claim 19, wherein the substrate support member (350) is comprised of one or more wires.

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