Patent ID: 12253483

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the various described embodiments. However, it will be apparent to one of ordinary skill in the art that the various described embodiments may be practiced without these specific details. In other instances, well-known methods, procedures, components, circuits, and networks have not been described in detail so as not to unnecessarily obscure aspects of the embodiments.

Many modifications and variations of this disclosure can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. The specific embodiments described herein are offered by way of example only, and the disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled.

Many superconductors require very low temperatures to operate in a superconducting state. However, operating superconducting circuitry at these low temperatures can be challenging. Achieving temperatures near absolute zero (e.g., via the use of lasers and/or magnetic fields), such as less than 1 Kelvin (K), 1-2 Kelvin, or 2-3 Kelvin, often requires high performance cooling systems that are large and costly. In particular, the challenges become significant as the desired temperature approaches zero. In addition, it is difficult to maintain the near-zero temperature due to high cooling power needed for reliable operation of many superconducting circuits. Therefore, there is a need for superconducting circuitry that is capable of operating in a superconducting state at higher temperatures (e.g., 3-4 Kelvin, 4-5 Kelvin, 5-10 Kelvin, etc.) and having consistent efficiency throughout an operational temperature range (e.g., 3-6 Kelvin). Moreover, there is a great need for manufacturing systems and methods to consistently and efficiently manufacture such superconducting circuitry.

FIGS.1A-1Bare diagrams illustrating a manufacturing system100in accordance with some embodiments. As shown inFIG.1A, the manufacturing system includes a chamber101having multiple inlets (e.g., inlets106and108) and an outlet112. In accordance with some embodiments, an apparatus within the chamber101includes a mount105for holding a substrate102(e.g., a silicon wafer) and a mount103for holding and positioning a sputter target110(e.g., niobium material) above the substrate102. In accordance with some embodiments, the apparatus includes a voltage source104electrically-coupling the mounts105and103. In some embodiments, the manufacturing system100is a CMOS system (e.g., a CMOS back-end-of-line (BEOL) system). In some embodiments, the manufacturing system100is a 200+ millimeter (mm) CMOS system.

FIG.1Bshows deposition of a superconducting layer on the substrate102(e.g., via a physical vapor deposition process) in accordance with some embodiments. In some embodiments, a buffer layer (e.g. composed of SiN) is deposited prior to deposition of the superconducting layer, e.g., as illustrated inFIGS.4A-4B. In some embodiments, the buffer layer is deposited via a chemical vapor deposition (CVD) process.FIG.1Bshows argon116entering the chamber101via a first inlet (e.g., the inlet106), nitrogen114entering the chamber101via a second inlet (e.g., the inlet108), and argon and nitrogen leaving the chamber101via the outlet112. In some embodiments, the inlets and/or the outlet112include valves (e.g., check valves) configured to (1) prevent reverse flow, (2) regulate a pressure within the chamber101, and/or (3) adjust relative percentages of the argon116and the nitrogen114. AlthoughFIG.1Bshows argon116, in some embodiments, argon116is replaced with a different noble gas (e.g., helium, neon, or krypton).

FIG.1Bfurther shows a plasma118forming between the sputter target110and the substrate102in accordance with some embodiments. In some embodiments, conditions within the manufacturing system100are adapted such that the plasma118forms between the sputter target110and the substrate102. For example, total pressure within the chamber101is maintained in the range of 10 milliTorr (mT) to 24 mT, or 12 mT to 15 mT. In some embodiments, the manufacturing system100is configured to operate in a first processing state, such as a processing state defined by process region202(FIG.2A) and process region204(FIG.2B), during deposition of a superconducting layer (e.g., composed of NbN) on the substrate102. In some embodiments, the substrate102is maintained at a temperature between 300 degrees Celsius and 400 degrees Celsius during deposition of the superconducting layer.

In some embodiments, conditions within the manufacturing system100are adapted such that niobium from the sputter target110transfers to the substrate102. For example, the voltage source104is maintained in the 2000 Watt (W) to 4000 W range with a duty cycle between 40% and 70%. In accordance with some embodiments, during transfer to the substrate102, the niobium from the sputter target110combines with nitrogen in the plasma118to form niobium nitride (NbN), and the NbN is deposited on the substrate102.

FIGS.2A-2Bare diagrams illustrating representative processing regions for manufacturing a superconductor device in accordance with some embodiments.FIG.2Ashows a process region202for deposition of a superconductor layer via a physical vapor deposition (PVD) process. The DC power axis inFIG.2Acorresponds to a power utilized by the voltage source104inFIGS.1A-1B. The pressure axis inFIG.2Acorresponds to a total pressure within the chamber101inFIGS.1A-1B. In some embodiments, the process region202is bounded by 10 mT and 24 mT. In some embodiments, the process region202is bounded by 12 mT and 15 mT. In some embodiments, the process region202is bounded by 2000 W and 4000 W. In some embodiments, the process region202is bounded by 2000 W and 2500 W. In some embodiments, the DC power range is dependent on a size of the substrate102, and the DC power range shown inFIG.2Acorresponds to a substrate102(e.g., a wafer) having an 8 inch diameter. In some embodiments, the DC power scales with size of the substrate. For example, the power is proportional to the surface area of the substrate (πr2).

FIG.2Bshows another process region204for deposition of the superconductor layer. The temperature axis inFIG.2Bcorresponds to a temperature of the substrate102inFIGS.1A-1B. The duty cycle percentage (%) axis inFIG.2Bcorresponds to a duty cycle utilized by the voltage source104inFIGS.1A-1B(e.g., an “on” percentage for the voltage source). In some embodiments, the process region204is bounded by 40% duty cycle and 60% duty cycle. In some embodiments, the process region204is bounded by 300 degrees Celsius and 400 degrees Celsius. In some embodiments, the process region204is bounded by 350 degrees Celsius and 400 degrees Celsius.

FIGS.3A-3Dare diagrams illustrating prophetic cubic phase peak ratios for a superconductor device in accordance with some embodiments.FIG.3Aillustrates a prophetic graph of cubic peak ratios between a (111) lattice structure (e.g., corresponding to an angle, of x-ray scattering, of 35.5 degrees) and a (200) lattice structure (e.g., corresponding to an angle of 41.2 degrees) as a function of a percentage of nitrogen in the plasma118for a deposited superconductor. In some embodiments, the percentage of nitrogen in the plasma is varied between a lower bound (e.g., 5% or 10%) and an upper bound (e.g., 15%, 25%, or 50%). In some embodiments and circumstances, the (111)/(200) ratio correlates with a threshold superconducting temperature of the deposited superconductor (e.g., the higher the (111)/(200) ratio the higher the threshold superconducting temperature).

In some embodiments, the graphs shown inFIGS.3B-3Dcorrespond to x-ray diffraction spectra of the deposited superconductor.FIG.3Bshows cubic peaks (111) and (200) for a deposited superconductor produced using a plasma having the nitrogen percentage corresponding to point302inFIG.3A. As illustrated inFIG.3Bthe ratio (111)/(200) is a fraction having a value less than 1 (indicating a low threshold superconducting temperature).FIG.3Cshows cubic peaks (111) and (200) for a deposited superconductor produced using a plasma having the nitrogen percentage corresponding to point304inFIG.3A. As illustrated inFIG.3Cthe ratio (111)/(200) is a fraction having a value greater than 1 (indicating a higher threshold superconducting temperature than inFIG.3B).FIG.3Dshows cubic peaks (111) and (200) for a deposited superconductor produced using a plasma having the nitrogen percentage corresponding to point306inFIG.3A. As illustrated inFIG.3Dthe ratio (111)/(200) is greater than the ratio (111)/(200) inFIG.3B, indicating a higher threshold superconducting temperature for a deposited superconductor produced using a plasma having the nitrogen percentage corresponding to point306inFIG.3Athan a deposited superconductor produced using a plasma having the nitrogen percentage corresponding to points302and304inFIG.3A.FIG.3Dalso shows a superlattice peak320at an angle (of x-ray scattering) of 50.9 degrees (e.g., corresponding to a |112| superlattice). In some embodiments and circumstances, the presence of the superlattice peak320indicates a higher threshold superconducting temperature than x-ray diffraction spectra without the superlattice peak320.

FIGS.4A-4Bare cross-sectional diagrams illustrating representative superconductor devices in accordance with some embodiments.FIG.4Ashows a cross-sectional view of a superconductor device400(e.g., a thick film superconductor). The superconductor device400includes a substrate402(e.g., a silicon wafer), a buffer layer404(e.g., composed of silicon nitride), and a superconductor layer406(e.g., composed of niobium nitride). In some embodiments, the thickness of the buffer layer404, denoted t1inFIG.4A, is in the range of 5 nanometers (nm) to 500 nm. In some embodiments, the thickness of the superconductor layer406, denoted t2inFIG.4A, is in the range of 40 nm to 1000 nm. In some embodiments, the thick film superconductor device400provides better x-ray diffraction spectra (e.g., to analyze to determine a preferred nitrogen percentage in the plasma used when depositing a superconductor layer) than a thin film superconductor. In some embodiments, the buffer layer404is deposited via a chemical vapor deposition process. In some embodiments, the superconductor layer406is deposited via a physical vapor deposition process (e.g., as illustrated inFIG.1B).

FIG.4Bshows a cross-sectional view of a superconductor device420(e.g., a thin film superconductor). The superconductor device420includes the substrate402, a buffer layer408(e.g., composed of silicon nitride), a second buffer layer410(e.g., composed of aluminum nitride), a superconductor layer412(e.g., composed of niobium nitride), and a protective layer414(e.g., composed of aluminum nitride). In some embodiments (not shown), the superconductor device420does not include the buffer layer408and/or the protective layer414. In some embodiments, the thickness of the buffer layer408, denoted t3inFIG.4B, is in the range of 5 nm to 500 nm. In some embodiments, the thickness of the buffer layer410, denoted t4inFIG.4B, is in the range of 3 nm to 50 nm. In some embodiments, the thickness of the superconductor layer412, denoted t4inFIG.4B, is in the range of 4 nm to 20 nm (e.g., in the range of 4 nm to 6 nm). In some embodiments, the thickness of the protective layer, denoted to inFIG.4B, is in the range of 1 nm to 5 nm.

FIGS.5A-5Care flow diagrams illustrating a method500of manufacturing superconductor devices in accordance with some embodiments. In some embodiments, the method500is performed with a manufacturing system (e.g., the manufacturing system100,FIG.1A). In some embodiments, the manufacturing system includes a physical vapor deposition (PVD) tool and/or a chemical vapor deposition (CVD) tool.

The method500includes manufacturing (502) a first superconductor device. In some embodiments, the first superconductor device includes a thick film superconductor layer (e.g., a superconductor layer having a thickness greater than 50 nm, 40 nm, or 30 nm). In some embodiments, the first superconductor device includes a silicon substrate, a buffer layer composed of silicon nitride, and a superconductor layer composed of niobium nitride. For example, the first superconductor is the superconductor device400(FIG.4A).

In some embodiments, manufacturing the first superconductor device includes obtaining (504) a substrate composed of silicon (e.g., a 8 inch diameter silicon wafer). In some embodiments, manufacturing the first superconductor device includes depositing (506) a first layer (e.g., the buffer layer404,FIG.4A) on the substrate, the first layer composed of silicon and nitrogen (e.g., composed of silicon nitride). In some embodiments, the first layer has a thickness in the range of 5 nm to 500 nm. In some embodiments, the first layer is deposited via a chemical vapor deposition (CVD) process (508).

In some embodiments, manufacturing the first superconductor device includes depositing (510) a superconductor layer on the first layer, the superconductor layer composed of niobium nitride. In some embodiments, the superconductor layer is deposited using the manufacturing system100discussed above with reference toFIG.1B. In some embodiments, the manufacturing is performed with CMOS BEOL processes and tools (e.g., a 200 mm+ CMOS tool).

In some embodiments, the superconductor layer is deposited via a physical vapor deposition (PVD) process (512), e.g., a reactive sputter deposition process. In some embodiments, the superconductor layer is deposited via an argon and nitrogen plasma (514), such as the plasma118inFIG.1B. In some embodiments, the argon is replaced with a different noble gas. In some embodiments, the argon and nitrogen plasma is maintained (516) at a pressure in the range of 10 milliTorr (mT) to 24 mT during the PVD process. In some embodiments, the pressure is maintained via selectively opening and closing the inlets106and108and the outlet112.

In some embodiments, depositing the superconductor layer includes transferring (518) niobium from a niobium sputter target (e.g., the sputter target110,FIG.1B) to the superconductor layer. In some embodiments, transferring the niobium includes supplying (520) a voltage to the niobium sputter target via a voltage source, where the voltage source is configured to utilize 2 kiloWatts (KW) to 4 kW of power (e.g., supplies a voltage greater than 1000 volts). In some embodiments, the voltage source comprises a pulsed direct current (DC) voltage source. In some embodiments, the pulsed DC voltage source has a duty cycle in the range of 40% and 70%. In some embodiments, transferring the niobium includes maintaining (522) the substrate at a temperature in the range of 300 degrees Celsius (° C.) to 400° C. during deposition of the superconductor layer.

The method500includes characterizing (524) the first superconductor device. Characterizing the first superconductor device includes obtaining (526) x-ray diffraction spectra of the first superconductor device. Characterizing the first superconductor device also includes identifying (528) a ratio of a first cubic phase peak to a second cubic phase peak in the x-ray diffraction spectra. In some embodiments, the first cubic phase peak corresponds (530) to a (111) lattice structure of niobium nitride (NbN) within the superconductor device, and the second cubic phase peak corresponds to a (200) lattice structure of the NbN. For example, the ratio illustrated inFIGS.3A-3D. In some embodiments, characterizing the first superconductor device includes determining (532) whether the x-ray diffraction spectra includes a superlattice phase peak for the NbN (e.g., the superlattice peak320,FIG.3D). In some embodiments, characterizing the first superconductor device includes determining whether the superlattice peak has a signal strength that is at least 30% of the signal strength of the (200) peak. In some embodiments, characterizing the first superconductor device includes determining whether a ratio of the superlattice peak to the (200) peak is at least a preset value (e.g., at least 1/4, 1/3, or 1/2).

The method500includes adjusting (534) one or more manufacturing parameters based on the identified ratio. In some embodiments, the one or more manufacturing parameters include (536) a percentage of nitrogen in the argon and nitrogen plasma (e.g., adjusting the percentage of nitrogen in the range of 5% to 50%). In some embodiments, the percentage of nitrogen in the plasma is varied between a lower bound (e.g., 5% or 10%) and an upper bound (e.g., 15%, 25%, or 50%) for a series of superconductor devices. For example, the nitrogen percentage is increased by 1% for each subsequent superconductor device (until a desired ratio is achieved). In some embodiments, the one or more manufacturing parameters include a duty cycle of a DC voltage source (e.g., the voltage source104,FIG.1B). For example, the duty cycle is adjusted within a range of 40% to 70%, or within a range of 40% to 60%. In some embodiments, the one or more manufacturing parameters include a wattage of the voltage source (e.g., the voltage source104,FIG.1B). For example, the wattage is adjusted within a range of 2 kW to 4 kW, or a range of 2 kW to 2.5 kW. In some embodiments, the one or more manufacturing parameters include a total pressure for the argon and nitrogen plasma (e.g., the plasma118). For example, the total pressure is adjusted within a range of 10 mT to 24 mT, or a range of 12 mT to 15 mT. In some embodiments, the one or more manufacturing parameters include a temperature of the substrate (e.g., the substrate102). For example, the temperature of the substrate is adjusted within a range of 300 degrees Celsius to 400 degrees Celsius, or a range of 350 degrees Celsius to 400 degrees Celsius. In some embodiments, the one or more manufacturing parameters include a thickness of the superconductor layer. For example, the thickness is adjusted from greater than 40 nm to less than 40 nm.

The method500includes manufacturing (538) a second superconductor device with the adjusted manufacturing parameter. In some embodiments, in accordance with a determination that the x-ray diffraction spectra include the superlattice phase peak (540), the second superconductor device is manufactured with a thin film superconductor layer (e.g., having a thickness less than 30 nm, 40 nm, or 50 nm). For example, the second superconductor device is manufactured with a superconductor layer having a thickness less than a predefined thickness. In some embodiments, the predefined thickness is a thickness value of 30 nm to 50 nm. In some embodiments, in accordance with a determination that the identified ratio is greater than a preset threshold (542), the second superconductor device is manufactured with a thin film superconductor layer (e.g., having a thickness less than 30 nm, 40 nm, or 50 nm). In some embodiments, the preset ratio threshold is a value in the range of 5 to 10. In some circumstances, a ratio greater than the preset threshold corresponds to a high threshold superconducting temperature (e.g., a TC≥15 Kelvin) for the superconductor device manufactured using the above-described manufacturing process. In some embodiments, a ratio greater than the preset threshold corresponds to a TC≥15 Kelvin for a thick superconductor device (e.g., with a superconductor layer having a thickness of at least 40 nm) and a TC≥12 Kelvin for a thin supercenter device (e.g., with a superconductor layer having a thickness below 40 nm, e.g., in the range of 4 nm to 6 nm). In some embodiments, in accordance with a determination that the identified ratio is less than the preset threshold (544), the second superconductor device is manufactured with a thick film superconductor layer (e.g., having a thickness greater than 30 nm, 40 nm, or 50 nm).

In some embodiments, manufacturing the second superconductor device includes depositing (546) a protective layer (e.g., the protective layer414,FIG.4B) over the superconductor layer. In some embodiments, the protective layer is composed of aluminum nitride. In some embodiments, the protective layer has a thickness in the range of 1 nm to 5 nm. In some embodiments, the protective layer is adapted to prevent oxidation of the superconductor layer. In some embodiments, manufacturing the second superconductor device includes, after depositing the protective layer, annealing (548) the second superconductor device. In some embodiments, addition of the protective layer allows for annealing of the superconductor device without damage to the superconductor layer. In some embodiments, the annealing includes annealing via an ex-situ annealing process with temperatures in the range of 500 degrees Celsius to 700 degrees Celsius.

As an example, the method500may include manufacturing multiple thick film superconductor devices (e.g., superconductor devices400), each manufactured using a deposition process having a plasma with a distinct nitrogen percentage. In this example, the thick film superconductor devices are characterized until one is found to have a (111)/(200) ratio greater than a preset threshold (e.g., greater than 5, 6, or 7). Once a thick film superconductor device is determined to have a ratio in excess of the preset threshold, the corresponding manufacturing parameters are identified and/or recorded, and a thin film superconductor device (e.g., superconductor devices420) is manufactured using the identified/recorded manufacturing parameters of the thick film superconductor device.

It will also be understood that, although the terms first, second, etc. are, in some instances, used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first current could be termed a second current, and, similarly, a second current could be termed a first current, without departing from the scope of the various described embodiments. The first current and the second current are both currents, but they are not the same condition unless explicitly stated as such.

The terminology used in the description of the various described embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various described embodiments and the appended claims, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “includes,” “including,” “comprises,” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

As used herein, a “superconducting circuit” or “superconductor circuit” is a circuit having one or more superconducting materials. For example, a superconductor switch circuit is a switch circuit that includes one or more superconducting materials. As used herein, a “superconducting” material is a material that is capable of operating in a superconducting state (under particular conditions). For example, a superconducting material is a material that operates as a superconductor (e.g., operates with zero electrical resistance) when cooled below a particular temperature (e.g., a threshold temperature) and having less than a threshold current flowing through it. A superconducting material is also sometimes called herein a superconduction-capable material. In some embodiments, the superconducting materials operate in an “off” state where little or no current is present. In some embodiments, the superconducting materials can operate in a non-superconducting state during which the materials have a non-zero electrical resistance (e.g., a resistance in the range of one thousand to ten thousand ohms). For example, a superconducting material supplied with a current greater than a threshold superconducting current for the superconducting material transitions from a superconducting state having zero electrical resistance to a non-superconducting state having non-zero electrical resistance.

The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the scope of the claims to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen in order to best explain the principles underlying the claims and their practical applications, to thereby enable others skilled in the art to best use the embodiments with various modifications as are suited to the particular uses contemplated.