Method of making high critical temperature metal nitride layer

Abstract

A method of manufacturing a device including a superconducting layer includes depositing a seed layer on a substrate, exposing the seed layer to an oxygen-containing gas or plasma to form a modified seed layer, and depositing a metal nitride superconducting layer directly on the modified seed layer after exposing the seed layer to the oxygen-containing gas or plasma. The seed layer is a nitride of a first metal, and the superconducting layer is a nitride of a different second metal.

Description

[Technical Field]

[0001] This disclosure relates to the use of seed layers to increase the superconducting critical temperature of metal nitride layers. [Previous Technology]

[0002] In the context of superconductivity, the critical temperature (TC) represents the temperature at which a material becomes superconducting. Niobium nitride (NbN) is a material that can be used in superconducting applications, such as superconducting nanowire single photon detectors (SNSPDs) for quantum information processing, defect analysis in CMOS and LiDAR, etc. The critical temperature of niobium nitride depends on the crystal structure and atomic ratio of the material. For example, referring to Figure 1, cubic delta-phase NbN has some advantages due to its relatively "high" critical temperature, such as 9.7 K to 16.5 K (the indicated process temperatures are for specific manufacturing processes and may not be applicable to other processes and deposition chamber designs).

[0003] Niobium nitride can be deposited on a workpiece by physical vapor deposition (PVD). For example, sputtering can be performed using a niobium target in the presence of nitrogen. Sputtering can be performed by inducing plasma in a reactor chamber containing the target and the workpiece. [Summary of the Invention]

[0004] In one embodiment, a method of manufacturing an element including a superconducting layer includes depositing a seed layer on a substrate, exposing the seed layer to an oxygen-containing gas or plasma to form a modified seed layer, and depositing a metal nitride superconducting layer directly on the modified seed layer after exposing the seed layer to an oxygen-containing gas or plasma. The seed layer is a nitride of a first metal, and the superconducting layer is a nitride of a different second metal.

[0005] In another embodiment, a method of manufacturing an element including a superconducting layer includes depositing a lower seed layer on a substrate, depositing an upper seed layer directly on the lower seed layer, and depositing a metal nitride superconducting layer directly on the upper seed layer. The lower seed layer is a nitride of a first metal, the upper seed layer is an oxide or oxynitride of the first metal, and the superconducting layer is a nitride of a different second metal.

[0006] In another embodiment, a method of manufacturing a device including a superconducting layer includes depositing a seed layer on a substrate and depositing a metal nitride superconducting layer directly on the seed layer. The seed layer is an oxide or oxynitride of a first metal, and the superconducting layer is a nitride of a different second metal.

[0007] In another embodiment, a method of manufacturing an element including a superconducting layer includes depositing a seed layer on a substrate at a first temperature, lowering the temperature of the substrate to a second temperature below the first temperature, raising the temperature of the substrate to a third temperature above the first temperature to form a modified seed layer, and directly depositing a metal nitride superconducting layer on the modified seed layer at the third temperature. The seed layer is a nitride of a first metal, and the superconducting layer is a nitride of a different second metal.

[0008] Implementation may include one or more of the following features.

[0009] Exposing the seed layer to oxygen-containing gas or plasma may include exposing the seed layer to pure oxygen. Depositing the seed layer on the substrate may include depositing a layer having a thickness of 3 nm to 50 nm. The upper seed layer may have a thickness of 0.1 nm to 1 nm or 3 nm to 50 nm. The temperature of the substrate may be reduced from a first temperature for depositing the seed layer to a lower second temperature, and this temperature may be increased to a third temperature higher than the second temperature for depositing the metal nitride superconducting layer.

[0010] Implementation may provide, but is not limited to, one or more of the following advantages. The critical temperature of the metal nitride layer (e.g., an NbN layer) can be increased. This allows for the fabrication of devices, such as SNSPDs, using superconducting wires with higher critical temperatures. The larger difference between the operating temperature (2 K to 3 K) and the critical temperature provides superior detection efficiency, lower dark counts, and potentially faster time response.

[0011] It should be noted that "superconductivity" indicates that the material becomes superconducting at the operating temperature of the device (e.g., 2 K to 3 K). The material is not actually superconducting during the manufacture of the device at or above room temperature, or when the device is not cooled for operation.

[0012] Details of one or more embodiments are set forth in the accompanying drawings and the following description. Other possible forms, features and advantages will become apparent from the embodiments, drawings and the scope of the claims.

Implementation Method

[0029] As mentioned above, niobium nitride (especially δ-phase NbN) has some advantages as a superconducting material. However, δ-phase NbN may be difficult to deposit with satisfactory quality. Furthermore, the greater the difference between the operating temperature (2 K to 3 K) and the critical temperature, the better the device performance. An aluminum nitride (AlN) layer can be used as a seed layer to increase the critical temperature of the NBN layer. Without being limited by any particular theory, the AlN seed layer can induce a crystalline structure in the NbN layer, which provides an increased critical temperature.

[0030] However, it has been surprisingly found that exposing the AlN seed layer to the atmosphere and at room temperature before depositing the NbN layer can actually provide a higher critical temperature than performing the NbN layer deposition on the AlN seed layer, for example, about 0.5 K higher, without disrupting the vacuum and lowering the substrate temperature. Again, without being limited by any particular theory, two non-exclusive possibilities have been proposed. First, exposing AlN to the atmosphere can result in the formation of a thin layer of alumina or alumina oxynitride on the surface of the AlN layer, which induces a superior crystalline structure in the NbN layer. Second, thermally cycling the AlN seed layer by lowering the substrate temperature from the first deposition temperature for AlN (e.g., 400°C) to room temperature (i.e., 20°C to 22°C) and then raising the substrate temperature back to the second deposition temperature for NbN (e.g., 400°C) may affect the stress in the AlN seed layer, which may affect its crystalline structure and consequently the crystalline structure of the NbN layer.

[0031] Figure 2A is a schematic diagram of some layers in element 100, including a metal nitride layer 108 used as a superconducting material. Figure 2B is a schematic diagram of element 100, wherein the metal nitride layer has been formed as, for example, a superconducting wire 108'. Element 100 may be a superconducting nanowire single-photon detector (SNSPD), a superconducting quantum interference device (SQUID), a circuit (e.g., RF circuitry) in a quantum computer, etc. Figures 3A to 3C are flowcharts of manufacturing method 200.

[0032] The metal nitride layer 108 is disposed on the support structure 102. The support structure 102 may include a substrate, such as a silicon wafer. The substrate may be a dielectric material, such as sapphire, SiO2, fused silica, or quartz; or a semiconductor material, such as silicon, gallium nitride (GaN), or gallium arsenide (GaAs). Although drawn as a single cube, the support structure 102 may include multiple underlying layers. For example, the support structure 102 may include a distributed Bragg reflector (DBR), which includes multiple pairs of layers formed of high-refractive-index and low-refractive-index materials deposited on the substrate, or a waveguide formed on the substrate.

[0033] The seed layer structure 103 is formed on the support structure 102. The seed layer structure 103 includes a lower seed layer 104 and an upper seed layer 106.

[0034] The lower seed layer 104 covers the top of the support structure 102, for example, in direct contact with the top surface of the support structure 102. The lower seed layer 104 is a metal nitride layer. Specifically, the lower seed layer 104 and the superconducting layer 108 are nitrides of different metals. The lower seed layer 104 may be aluminum nitride (AlN). However, hafnium nitride (HfN), chromium nitride (CrN), or nitrides of alloys of aluminum with hafnium or scandium may also be suitable.

[0035] The lower seed layer 104 may have a thickness of about 3 nm to 50 nm, for example, about 5 nm, about 10 nm, or about 20 nm. The lower seed layer 104 may have a (002) c-axis crystal orientation. The lower seed layer 104 does not need to be superconducting at the operating temperature of the device 100. The lower seed layer 104 may be deposited (step 202) by a standard chemical vapor deposition or physical vapor deposition process. The deposition process may be performed on a substrate at a temperature of 200°C to 500°C (e.g., 400°C).

[0036] The exemplary processing parameters for the lower seed layer are: a power of 1 kW to 5 kW applied to the sputtering target; a total pressure of 2 mTorr to 20 mTorr (nitrogen and inert gas) supplied in a ratio between 3:100 and 6:1 (e.g., about 3:1); a wafer temperature of 200°C to 500°C; and no bias voltage applied to the wafer.

[0037] An upper seed layer 106 is formed on top of a lower seed layer 104, for example, in direct contact with the top surface of the lower seed layer 104 (step 204). The upper seed layer 106 is a metal oxide or metal oxynitride layer. Specifically, the upper seed layer 106 is an oxide or oxynitride of a metal that is the same metal as the metal nitride in the lower seed layer 104. The upper seed layer 106 may be aluminum oxide or aluminum oxynitride, as this appears to increase the critical temperature of NbN, for example, by about 0.5 K compared to aluminum nitride as a seed layer. However, hafnium oxide or hafnium oxynitride, chromium oxide or chromium oxynitride, or nitrides or oxynitrides of aluminum alloys with hafnium or scandium may also be suitable.

[0038] The upper seed layer 106 may be thinner than the lower seed layer 104. Depending on the manufacturing method, the upper seed layer 106 may be about 0.1 nm to 3 nm thick. In some embodiments, the upper seed layer 106 is only one to five atomic layers thick, for example, two to three atomic layers thick. The upper seed layer 106 may have a (002) c-axis crystal orientation. The upper seed layer 106 does not need to be superconducting at the operating temperature of the device 100.

[0039] Referring to Figure 3A, one technique for forming the upper seed layer 106 of metal oxide or metal nitride is to expose the lower seed layer 104 to a gas containing oxygen and / or water (step 204a). For example, the lower seed layer 104 may be exposed to air. As another example, the lower seed layer 104 may be exposed to pure oxygen. As another example, the lower seed layer 104 may be exposed to a gas mixture containing 20% ​​to 90% by volume oxygen and one or more other gases, such as nitrogen and / or rare gases (e.g., argon). In some embodiments, the gas mixture includes water, for example, water vapor or steam. The pressure may be from 1 Torr to 1 atmosphere, for example, 0.8 to 1 atmosphere.

[0040] Referring to Figure 3B, another technique for forming the upper seed layer 106, using a metal oxide or metal nitride, is to expose the lower seed layer 104 to a gas containing oxygen (O2) plasma (step 204b). For example, the lower seed layer 104 can be exposed to pure oxygen plasma. For example, oxygen can be directed into a plasma processing chamber, and the oxygen plasma can be formed at a power of approximately 100 W. The pressure can be from 2 mTorr to 500 mTorr. Generally, a relatively high pressure, such as 100 mTorr to 500 mTorr, can be used in a dedicated chamber for oxygen plasma processing, while a relatively low pressure, such as 2 mTorr to 15 mTorr, can be used if oxygen plasma processing is performed in the same chamber used for depositing the lower seed layer.

[0041] Without being restricted by any particular theory, exposing AlN to oxygen can result in the formation of a thermal oxide or thermal nitride layer (i.e., an aluminum oxide or aluminum oxynitride layer) on the surface of the AlN layer.

[0042] In some embodiments, the substrate having the lower seed layer is lowered from a first temperature (e.g., 300°C to 500°C) at which the lower seed layer is deposited to a lower second temperature (e.g., 20°C to 300°C). The lower seed layer is exposed to oxygen-containing gas or plasma at the lower second temperature. The second temperature may be at least 200°C lower than the first temperature. For example, the second temperature may be room temperature, i.e., 20°C to 22°C. The substrate is then raised to an elevated third temperature for depositing the metal nitride for the superconducting layer.

[0043] In some embodiments, the substrate having the lower seed layer is maintained at a high temperature, for example, at 300°C or above, for example, at the same temperature at which the lower seed layer is deposited (e.g., 400°C), and the substrate is exposed to oxygen-containing gas or plasma at this high temperature.

[0044] In some embodiments, the substrate having the lower seed layer is lowered from a first temperature to a second temperature, and then raised to an elevated third temperature (e.g., at or above 300°C, for example, 300°C to 500°C), and the lower seed layer is exposed to oxygen-containing gas or plasma at the elevated third temperature.

[0045] The exposure time can depend on the pressure and temperature, and can range from 1 second to 120 minutes. For example, the exposure time to the atmosphere at room temperature can be about 45 minutes. As another example, the exposure time to oxygen plasma (where the substrate is at the same temperature as the deposited seed layer (e.g., about 400°C)) can be about 30 seconds.

[0046] In the techniques shown in Figures 3A and 3B, the upper seed layer 106 is actually a primary oxide or primary oxynitride formed on the underlying metal nitride layer, and is therefore expected to be two to four atomic layers thick. For example, the upper seed layer 106 can be up to about 1 nm thick.

[0047] Referring to Figure 3C, another technique for forming the upper seed layer 106, namely the metal oxide or metal oxynitride, is to deposit the upper seed layer 106 by physical vapor deposition. Example processing parameters for the upper seed layer include a power of 1 kW to 5 kW applied to the sputtering target, a total pressure (oxygen and inert gas) of 2 mTorr to 20 mTorr supplied at a ratio between 3:100 and 6:1, and a wafer temperature of 200°C to 500°C. CVD and ALD techniques for depositing alumina or aluminum oxynitride also exist.

[0048] In the technique shown in Figure 3C, the thickness of the upper seed layer 106 depends on the processing time or the number of iterations of the deposition process. For example, the thickness of the upper seed layer 106 can be 1 nm to 2 nm.

[0049] Referring to Figures 2A and 2B, a superconducting metal nitride layer 108 is deposited on the upper seed layer 106, for example, in direct contact with the upper seed layer 106. The metal nitride layer 108 is formed of niobium nitride (NbN), titanium nitride (TiN), or niobium titanium nitride (NbxTi1-xN). The superconducting layer 108 may have a thickness of 4 nm to 50 nm, for example, about 5 nm, about 10 nm, or about 20 nm.

[0050] The metal nitride layer 108 can be deposited using standard chemical vapor deposition or physical vapor deposition processes. Exemplary processing parameters include a base pressure of 1e-8 Torr, a power applied to the target of 1 kW to 3 kW, a total pressure of 5 mTorr to 7 mTorr during processing, a wafer temperature of 400°C, no bias voltage applied to the wafer, and a percentage of gas (such as N2) sufficient to obtain cubic delta-phase NbN. In some implementations, for example by switching to a new target, the metal nitride layer 108 can be deposited in the same processing chamber used for depositing the lower seed layer 104 and the upper seed layer 106. This allows for higher throughput fabrication. Alternatively, the substrate can be transported to different deposition chambers without disrupting the vacuum. This allows for the deposition of the metal nitride layer without exposing the seed layer to the atmosphere and with a lower risk of contamination.

[0051] After depositing the metal nitride layer 108, a capping layer 110 may be deposited on the metal nitride layer 108 (step 208). The capping layer 110 acts as a protective layer, for example, to prevent oxidation or other types of contamination or damage to the metal nitride layer 108. The capping layer 108 may be a dielectric, but does not need to be superconducting at the operating temperature of the device 100. The capping layer 108 may be amorphous silicon (a-Si). In some embodiments, the capping layer 108 is a nitride of a material different from the metal nitride used for the superconducting layer 108. Examples of materials used for the capping layer 108 include AlN, Al2O3, SiO2, and SiN. The capping layer 108 may be deposited by standard chemical vapor deposition or physical vapor deposition processes.

[0052] An etching process may be used to form a trench 112 through at least the metal nitride layer 108 to form the superconducting wire 108' or other structures required for the device 100 (step 210). The wire 108' may have a width of about 25 nm to 250 nm, for example, about 60 nm. Although Figure 2B illustrates the trench 112 as extending through the metal nitride layer 108 and the capping layer 110 and not extending into the upper seed layer 106, other configurations are possible. As an example, the trench 112 may extend partially into or completely through the upper seed layer 106, or completely through the upper seed layer 106 and partially into or completely through the lower seed layer 104.

[0053] Air may contain contaminants, therefore, for any of the above-described processes, the upper seed layer 106 can be formed on the lower seed layer 104 without breaking the vacuum. For example, the substrate is not removed from the deposition chamber in which the lower seed layer is deposited, or the vacuum is not broken during the transfer of the substrate from the deposition chamber in which the lower seed layer is deposited to the chamber in which the upper seed layer is formed. Similarly, a metal nitride superconducting layer 108 can be formed on the upper seed layer 106 without breaking the vacuum.

[0054] When forming the upper seed layer 106 by oxygen plasma treatment (see Figure 3B) or by PVD (see Figure 3C), the application material Endura® with pulsed PVD can be used. The deposition of the lower seed layer and the oxygen plasma treatment or PVD of oxides or oxynitrides can be performed in the same chamber. NbN deposition can be performed in different chambers of the same Endura tool without disrupting the vacuum.

[0055] Figure 4A is a schematic diagram of some layers in element 100', including a metal nitride layer 108 used as a superconducting material. Figure 4B is a schematic diagram of element 100', wherein the metal nitride layer has been formed as a feature, for example, a superconducting wire 108'. Element 100' is similar to element 100, but the seed layer structure 103 of element 100' has a single metal oxide or metal nitride seed layer 106', instead of having a lower seed layer and an upper seed layer. Element 100' can be configured and manufactured as discussed with respect to element 100, except as described below. Figure 5 is a flowchart of the manufacturing method 200'.

[0056] A seed layer 106' is disposed on top of the support structure 102. The seed layer 106' is a metal oxide or metal oxynitride. Specifically, the seed layer 106' is an oxide or oxynitride of a metal different from the metal nitride in the superconducting layer 108. The seed layer 106' can be aluminum oxide or aluminum oxynitride (AlN), as this appears to increase the critical temperature of NbN, for example, by about 0.5 K compared to aluminum nitride as a seed layer. However, hafnium oxide, hafnium oxynitride, gallium oxide, or gallium oxynitride may also be suitable. Unlike element 100, there is no metal nitride layer of the same metal in direct contact with the bottom of the metal oxide or oxynitride seed layer 106'.

[0057] The seed layer 106' may have a thickness of about 3 nm to 50 nm, for example, about 5 nm, about 10 nm, or about 20 nm. The seed layer 106' may have a (002) c-axis crystal orientation. The seed layer 106' does not need to be superconducting at the operating temperature of the device 100. The seed layer 106' may be deposited (step 204') by a standard chemical vapor deposition or physical vapor deposition process. The deposition process may be performed on a substrate at a temperature of 200°C to 500°C (e.g., 400°C).

[0058] The exemplary processing parameters are a power of 1 kW to 5 kW applied to the sputtering target, a total pressure of 2 mTorr to 20 mTorr (nitrogen and inert gas) supplied in a ratio between 3:100 and 1:6, a wafer temperature of 200°C to 500°C, and no bias voltage applied to the wafer.

[0059] The application material Endura® with pulsed PVD can be used for the deposition of seed layers and superconducting layers. For example, alumina deposition can be performed in the first chamber, and NbN deposition can be performed in different chambers of the same tool without disrupting the vacuum.

[0060] Thermal cycling can be applied between the deposition of the seed layer 106' and the superconducting layer 108. For example, the substrate having the seed layer 106' is lowered from a first temperature to a second temperature, and then raised to a third temperature for depositing the metal nitride superconducting layer 108, for example, at or above 300°C, such as 300°C to 500°C. Alternatively, the substrate having the seed layer 106' can be maintained at a high temperature, for example, at or above 300°C, such as at the same temperature for depositing the seed layer 106', until the metal nitride superconducting layer 108 is deposited.

[0061] Figure 6A is a schematic diagram of some layers in element 100" including a metal nitride layer 108 used as a superconducting material. Figure 6B is a schematic diagram of element 100" in which the metal nitride layer has been formed as a feature, for example, a superconducting wire 108'. Element 100" is similar to element 100', but the seed layer structure 103 of element 100" includes a single layer of metal nitride that has undergone thermal cycling, rather than a seed layer having metal oxide or metal oxynitride. Except as discussed below, element 100" can be configured and manufactured as discussed with respect to elements 100 and 100'. Figure 7 is a flowchart of manufacturing method 200".

[0062] A seed layer 104' is disposed on top of the support structure 102. The seed layer 104' is a metal nitride. Specifically, the seed layer 104' and the superconducting layer 108 are nitrides of different metals. The seed layer 104' can be aluminum nitride. However, hafnium nitride or gallium nitride can also be suitable. Unlike element 100, there is no metal oxide or metal oxynitride between the seed layer 104' and the superconducting layer 108.

[0063] The seed layer 104' can be deposited directly on the support structure 102 by a standard chemical vapor deposition or physical vapor deposition process (step 204'). The deposition process can be performed on a substrate at a first temperature of 200°C to 500°C (e.g., 400°C).

[0064] After deposition, the substrate having the metal nitride seed layer undergoes thermal cycling (step 205). Specifically, the substrate having the seed layer is cooled from a first temperature (e.g., 200°C to 500°C) at which the seed layer was deposited to a lower second temperature. For example, the substrate having the seed layer 104' is cooled from the first temperature (e.g., 300°C to 500°C) at which the seed layer was deposited to a lower second temperature (e.g., 20°C to 300°C). The second temperature may be at least 200°C lower than the first temperature. For example, the second temperature may be room temperature, i.e., 20°C to 22°C. The seed layer may undergo thermal cycling while in a vacuum or exposed to nitrogen and / or an inert gas (e.g., argon). The substrate is then cooled to an elevated third temperature, e.g., 300°C to 500°C, for depositing the metal nitride for the superconducting layer. Thermal cycling may alter the crystal structure of the seed layer 104'.

[0065] After thermal cycling, a metal nitride superconducting layer 108 can be deposited on the seed layer 104'. The superconducting layer 108 is deposited without breaking the vacuum or otherwise exposing the seed layer to oxygen or oxygen-containing vapor (e.g., H2O).

[0066] Figures 8A and 8B respectively show a top view and a side view of the element 100a configured as a superconducting nanowire single-photon detector (SNSPD). The element 100a may use any of the above-described seed layer 103 configurations.

[0067] The SNSPD element 100a may include at least one superconducting wire 108' disposed on the support structure 102. The superconducting wire 108' may be connected between the conductive electrodes 120. The superconducting wire 108' may be arranged in a zigzag pattern (e.g., back-and-forth parallel lines) on the support structure 102. In some embodiments, multiple wires 108' are connected in parallel between the electrodes 120, wherein each wire 108' covers a separate area 152, but it is possible that only a single wire 108' covers the entire detection area of ​​the element 100a. In addition, many other patterns are possible, such as zigzag or double helix.

[0068] The support structure 102 includes a substrate 124 and a distributed Bragg reflector (DBR) 126, which includes multiple pairs of layers formed of high-refractive-index and low-refractive-index materials.

[0069] The SNSPD element 100a operates by bringing photons (illustrated as beam 10) close to the top of the element 100a (e.g., perpendicularly incident relative to the substrate 124). The SNSPD element operates by having photons to be detected enter from the top and irradiate the SNSPD. Upon initial impact or after reflection from the DBR, photon absorption creates hotspots on the NbN nanowires. These hotspots raise the temperature of the NbN above the critical temperature, causing a portion of the conductor to cease to be superconducting. Current congestion may occur in the area around the hotspots, resulting in current densities exceeding the critical current density, which may disrupt the superconducting state of the entire conductor. The change from the superconducting state to a normal resistive state of the NbN conductor can be detected electrically by allowing current to flow through the element and monitoring the voltage difference between the electrodes.

[0070] Another form of the superconducting nanowire single-photon detector (SNSPD) element includes a waveguide for inputting photons into the detector along an axis generally parallel to the surface of the substrate. Figures 9A and 9B illustrate an element 100b configured as a superconducting nanowire single-photon detector (SNSPD) and having a waveguide 138. Element 100b may use any of the above-described arrangements of the seed layer 103.

[0071] The SNSPD element 100b may include at least one superconducting wire 108' disposed on the support structure 102. Several superconducting wires 108' may be arranged to form a plurality of parallel lines, wherein adjacent lines are connected at alternating ends. Although Figure 9A illustrates four parallel lines, the element may have only two parallel lines (e.g., U-shaped wires) or a greater number of lines. The superconducting wires 108' may be connected between conductive electrodes.

[0072] The support structure 102 may include a substrate 134, a dielectric layer 136 on the substrate 134, and a waveguide 138 disposed on the dielectric layer 136. The dielectric layer 102c is a first material having a first refractive index, and the waveguide 102d is a second material having a second refractive index higher than the first refractive index.

[0073] Photons indicated by beam 10b are injected into the device from the side (e.g., generally parallel to the top surface of substrate 132) via waveguide 138. Specifically, photons may enter along an axis (indicated by arrow A) that is generally parallel to a line parallel to the conductor 108'.

[0074] Additionally, along an axis transverse to the direction of light propagation, the conductor 108' may be located near the center of the waveguide 138. For example, on each side of the element, a gap 130 may exist between the outer edge of the conductor 108' and the outer edge of the waveguide 138. This gap 130 may have a width of approximately 25% to 30% of the total width of the waveguide.

[0075] Generally speaking, because the dielectric layer 136 below the waveguide 138 and the empty space or air above the waveguide 138 both have a lower refractive index than the waveguide 138, photons in the waveguide 138 are captured by total internal reflection. However, due to the optical coupling between the waveguide 138 and the nanowire 108', photons can escape into the nanowire 108' and thus be absorbed by the nanowire 108'. In this type of device, the optical coupling efficiency can be very high.

[0076] Referring to Figure 9C, if waveguide 138 is formed of a suitable metal nitride (e.g., aluminum nitride), the top surface of waveguide 138 can provide a lower seed layer and can be processed to form an upper seed layer 106, or the upper seed layer 106 can be formed directly on waveguide 108, that is, it is not necessary to deposit a separate lower seed layer.

[0077] While specific embodiments have been described, other and additional embodiments may be devised without departing from the basic scope of this disclosure. Elements and features of one embodiment are expected to be advantageously incorporated into other embodiments without further description. However, it should be noted that the drawings illustrate only exemplary embodiments. The scope of this invention is defined by the following claims. [Simplified Explanation of the Diagram]

[0013] Figure 1 is a diagram showing the phase of niobium nitride as a function of processing temperature and the percentage of nitrogen atoms.

[0014] Figure 2A is a schematic cross-sectional view of a device including a lower seed layer of metal nitride, an upper seed layer of metal oxide or oxynitride, and a superconducting metal nitride layer.

[0015] Figure 2B is a schematic cross-sectional view of the element in Figure 2A, wherein the superconducting layer has been etched to form a superconducting wire.

[0016] Figures 3A to 3C are flowcharts of methods for manufacturing the components in Figure 2A or Figure 2B.

[0017] Figure 4A is a schematic cross-sectional view of a device including a metal oxide or nitride seed layer and a superconducting metal nitride layer.

[0018] Figure 4B is a schematic cross-sectional view of the element in Figure 4A, wherein the superconducting layer has been etched to form a superconducting wire.

[0019] Figure 5 is a flowchart of a method for manufacturing the component in Figure 4A or Figure 4B.

[0020] Figure 6A is a schematic cross-sectional view of a device including a metal nitride seed layer and a superconducting metal nitride layer.

[0021] Figure 6B is a schematic cross-sectional view of the element in Figure 6A, wherein the superconducting layer has been etched to form a superconducting wire.

[0022] Figure 7 is a flowchart of a method for manufacturing the component shown in Figure 6A or Figure 6B.

[0023] Figure 8A is a schematic top view of an SNSPD including a distributed Bragg reflector.

[0024] Figure 8B is a schematic cross-sectional side view of the element in Figure 8A.

[0025] Figure 9A is a schematic top view of the SNSPD including the waveguide.

[0026] Figure 9B is a schematic cross-sectional side view of the element in Figure 9A.

[0027] Figure 9C is a schematic cross-sectional side view of another embodiment of the element in Figure 9A.

[0028] The same element symbols and names in various diagrams indicate the same element. [Biomaterial Storage]

[0079] Domestic Deposit Information (Please note in order of deposit institution, date, and number) None

[0080] Overseas Deposit Information (Please note in the order of deposit country, institution, date, and number) None

Claims

1. A superconducting device, comprising: a dielectric or semiconductor substrate; a nitride seed layer disposed on the substrate, the nitride seed layer being a nitride of a first metal; a metal nitride superconducting layer directly disposed on the seed layer and patterned to form a line, the metal nitride superconducting layer being a nitride of a different second metal, wherein the second metal is niobium, titanium, or an alloy of niobium and titanium; and a capping layer, the capping layer being amorphous silicon, an oxide, or a metal nitride, the metal nitride being a silicon nitride, a nitride of the first metal, or a nitride of a different third metal.

2. The superconducting element as described in claim 1, wherein the second metal is niobium.

3. The superconducting element as described in claim 2, wherein the first metal is aluminum.

4. The superconducting element as described in claim 1, wherein the first metal is aluminum.

5. The superconducting device as claimed in claim 1, wherein the oxynitride seed layer has a thickness of 1 to 3 nm.

6. The superconducting element as claimed in claim 5, wherein the metal nitride superconducting layer has a thickness of 4 to 50 nm.

7. The superconducting element as claimed in claim 1, wherein the capping layer is an oxide of the first metal.

8. The superconducting element as described in claim 7, wherein the first metal is aluminum.

9. The superconducting element as claimed in claim 1, wherein the capping layer is an oxide of the first metal.

10. The superconducting element as claimed in claim 9, wherein the first metal is aluminum.

11. The superconducting element as claimed in claim 1, wherein the capping layer is silicon oxide or silicon nitride.

12. The superconducting element as claimed in claim 1, wherein the capping layer is a nitride of one of the different third metals.

13. The superconducting device as claimed in claim 1, wherein the capping layer is amorphous silicon.

14. The superconducting element as claimed in claim 1, wherein the line has a width of 25 to 250 nm.

15. The superconducting element as claimed in claim 1, wherein the plurality of trenches that pass through the metal nitride superconducting layer to form the isotherms do not extend to the seed layer.

16. The superconducting element as claimed in claim 1, wherein a plurality of trenches through the metal nitride superconducting layer to form the lines also extend to the seed layer.

17. The superconducting element as claimed in claim 1, wherein a plurality of trenches pass through the capping layer and through the metal nitride superconducting layer to form the isolines.

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